U.S. patent application number 10/588212 was filed with the patent office on 2008-08-14 for combustion apparatus.
This patent application is currently assigned to EBARA CORPORATION. Invention is credited to Shunsuke Amano, Masataka Arai.
Application Number | 20080193886 10/588212 |
Document ID | / |
Family ID | 34836111 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080193886 |
Kind Code |
A1 |
Amano; Shunsuke ; et
al. |
August 14, 2008 |
Combustion Apparatus
Abstract
A combustion apparatus according to the present invention can
positively control and generate burnt gas recirculation with a
simple structure. The combustion apparatus has an annular container
(12) having an inner cylindrical portion (15) forming an inner
circumferential side surface, an outer cylindrical portion (13)
forming an outer circumferential side surface, an open end (26),
and a close end (10). A flow (28) of air is formed so as to have a
velocity component in the direction of a central axis (J) from the
open end (26) to the close end (10) and a velocity component to
swirl in a circumferential direction of the annular container (12).
Fuel (23) is injected so as to have a velocity component in the
direction of the central axis (J) from the close end (10) to the
open end (26) and a velocity component directed radially
outward.
Inventors: |
Amano; Shunsuke; (Kanagawa,
JP) ; Arai; Masataka; (Gunma, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
EBARA CORPORATION
Ohta-ku, Tokyo
JP
|
Family ID: |
34836111 |
Appl. No.: |
10/588212 |
Filed: |
February 9, 2005 |
PCT Filed: |
February 9, 2005 |
PCT NO: |
PCT/JP05/02371 |
371 Date: |
February 28, 2007 |
Current U.S.
Class: |
431/9 |
Current CPC
Class: |
F23R 3/06 20130101; F23C
9/006 20130101; F23R 3/46 20130101; F23R 3/50 20130101; F23C 7/02
20130101; F23C 3/006 20130101 |
Class at
Publication: |
431/9 |
International
Class: |
F23M 3/02 20060101
F23M003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2004 |
JP |
2004-032941 |
Claims
1. A combustion apparatus comprising: an annular container having
an inner cylindrical portion forming an inner circumferential side
surface, an outer cylindrical portion forming an outer
circumferential side surface an open end, and a close end; an air
supply portion for supplying combustion air into said annular
container so as to have a velocity component in a direction of a
central axis of said annular container from said open end to said
close end of said annular container; and a fuel supply portion for
supplying fuel into said annular container so as to have a velocity
component in the direction of the central axis of said annular
container from said close end to said open end of said annular
container, wherein a flow of the combustion air supplied into said
annular container first crosses a track of the fuel at a region
away from said fuel supply portion and then crosses the track of
the fuel again at a region near said fuel supply portion.
2. A combustion apparatus comprising: an annular container having
an inner cylindrical portion forming an inner circumferential side
surface, an outer cylindrical portion forming an outer
circumferential side surface, an open end, and a close end; an
inflow passage for supplying combustion air into said annular
container said inflow passage being formed at a location away from
said close end in a direction of a central axis of said annular
container so as to extend through said outer circumferential side
surface of said annular container; and a fuel nozzle provided
inside of said close end of said annular container for supplying
fuel into said annular container, wherein said inflow passage is
configured so as to form a flow of the air with a velocity
component in the direction of the central axis of said annular
container from said open end to said close end and a velocity
component to swirl in a circumferential direction of said annular
container, wherein said fuel nozzle is configured so as to inject
the fuel toward said inflow passage with a velocity component in
the direction of the central axis of said annular container from
said close end to said open end and a velocity component directed
radially outward.
3. A combustion apparatus comprising: an annular container having
an inner cylindrical portion forming an inner circumferential side
surface, an outer cylindrical portion forming an outer
circumferential side surface an open end, and a close end; an
inflow passage for supplying combustion air into said annular
container; and a fuel nozzle for supplying fuel into said annular
container, wherein said outer cylindrical portion has a portion
having a reduced diameter at a location away from said close end
along a central axis of said annular container by a predetermined
distance, wherein said inflow passage is formed at said portion
having a reduced diameter in said outer cylindrical portion and is
configured so as to for a flow of the air with a velocity component
in the direction of the central axis of said annular container from
said open end to said close end and a velocity component to swirl
in a circumferential direction of said annular container, wherein
said fuel nozzle is configured so as to inject the fuel toward said
inflow passage with a velocity component in the direction of the
central axis of said annular container from said close end to said
open end and a velocity component directed radially outward.
4. A combustion apparatus comprising: an annular container having
an inner cylindrical portion forming an inner circumferential side
surface, an outer cylindrical portion forming an outer
circumferential side surface, an open end, and a close end; a
cylindrical member disposed substantially coaxially with a central
axis of said annular container and positioned on said open end side
of said outer cylindrical portion, said cylindrical member having a
diameter smaller than that of said outer cylindrical portion; an
annular connecting member connecting an end of said outer
cylindrical portion and an outer circumferential surface of said
cylindrical member to each other; an inflow passage formed in said
connecting member for supplying combustion air into said annular
container; and a fuel nozzle provided inside of said close end of
said annular container for supplying fuel into said annular
container, wherein said inflow passage is configured so as to form
a flow of the air with a velocity component in the direction of the
central axis of said annular container from said open end to said
close end and a velocity component to swirl in a circumferential
direction of said annular container, wherein said fuel nozzle is
configured so as to inject the fuel toward said inflow passage with
a velocity component in the direction of the central axis of said
annular container from said close end to said open end and a
velocity component directed radially outward.
5. A combustion apparatus comprising: an annular container having
an inner cylindrical portion forming an inner circumferential side
surface, an outer cylindrical portion forming an outer
circumferential side surface, an open end, and a close end; an
annular member disposed substantially coaxially with a central axis
of said annular container and positioned on said open end side,
said annular member having an inner cylindrical portion forming an
inner circumferential side surface and an outer cylindrical portion
forming an outer circumferential side surface and having a diameter
smaller than that of said outer cylindrical portion of said annular
container; a first connecting member connecting an end surface, on
said open end side, of said outer cylindrical portion of said
annular container and an outer circumferential surface of said
outer cylindrical portion of said annular member to each other; a
second connecting member connecting an end surface, on said open
end side, of said inner cylindrical portion of said annular
container and an end surface of said inner cylindrical portion of
said annular member to each other; an inflow passage formed in said
first connecting member for supplying combustion air into said
annular container; and a fuel nozzle provided inside of said close
end of said annular container for supplying fuel into said annular
container wherein said inflow passage is configured so as to form a
flow of the air with a velocity component in the direction of the
central axis of said annular container from said open end to said
close end and a velocity component to swirl in a circumferential
direction of said annular container, wherein said fuel nozzle is
configured so as to inject the fuel toward said inflow passage with
a velocity component in the direction of the central axis of said
annular container from said close end to said open end and a
velocity component directed radially outward.
6. The combustion apparatus as recited in claim 2, wherein an
additional inflow passage is provided in said inner cylindrical
portion of said annular container for supplying air into said
annular container.
7. The combustion apparatus as recited in claim 2, wherein an
additional inflow passage is provided on said close end at a
location near said inner cylindrical portion of said annular
container and is positioned radially inward from said fuel nozzle
so that air flows in the direction of the central axis of said
annular container.
8. The combustion apparatus as recited in claim 2, wherein an
additional inflow passage is provided in said outer cylindrical
portion of said annular container for supplying air inwardly in a
radial direction of said annular container.
9. The combustion apparatus as recited in claim 2, further
comprising a flow adjusting structure disposed on said close end
within said annular container and/or on said outer cylindrical
portion of said annular container near said close end for
suppressing a swirling flow of the air near said close end.
10. The combustion apparatus as recited in claim 2, further
comprising a flow adjusting structure disposed on said close end
within said annular container and/or on said outer cylindrical
portion of said annular container near said close end for
converting a flow of air having a velocity component in a direction
of the central axis of said annular container from said open end to
said close end and swirling in a circumferential direction of said
annular container into a flow directed inwardly in a radial
direction of said annular container near said close end.
11. The combustion apparatus as recited in claim 2, wherein an
additional fuel nozzle is provided at a location closer to said
close end than said inflow passage with respect to the direction of
the central axis of said outer cylindrical portion of said annular
container.
Description
TECHNICAL FIELD
[0001] The present invention relates to a combustion apparatus, and
more particularly to a combustion apparatus for supplying
combustion air and fuel to a combustion chamber to mix and combust
the combustion air and the fuel.
BACKGROUND ART
[0002] Regulation regarding air pollutants discharged from a
combustion apparatus, particularly nitrogen oxide (NOx), becomes
stricter and stricter. Thus, there has been demanded technology to
reduce discharge of NOx.
[0003] Nitrogen oxide (NOx) is generally classified according to
its generation mechanism into three types: thermal NOx, prompt NOx,
and fuel NOx. Thermal NOx is generated when nitrogen in air reacts
with oxygen at a high temperature, and greatly depends on
temperature. Prompt NOx is generated particularly in a flame of
fuel-rich condition. Fuel NOx is generated while nitrogenous
compounds contained in fuel are converted.
[0004] Recently, clean fuel including no nitrogenous compounds has
been used in many cases. In such cases, fuel NOx is hardly
generated. When a design of fuel-rich combustion is modified into a
design of lean combustion in order to reduce prompt NOx, the
generation of prompt NOx can be suppressed. As compared to the
aforementioned reduction of fuel NOx and prompt NOx, reduction of
thermal NOx is most difficult and is becoming a key of NOx
reduction technology in recent years.
[0005] Here, it is important to lower a combustion temperature in
order to reduce thermal NOx. Technology to lower a combustion
temperature includes premixed combustion, particularly lean
premixed combustion, pre-evaporation, rich and lean combustion,
two-stage combustion, burnt gas recirculation, and the like.
[0006] In a case of gaseous fuel, a uniform distribution of fuel
concentration can be achieved by premixed combustion in which fuel
is sufficiently mixed with air, then ignited, and combusted, and a
combustion temperature can be lowered particularly by premixed
combustion in fuel-lean condition. However, premixed combustion has
problems that a stable combustion range is so narrow that backfire
or blow-off is likely to occur. Further, there is a defect that
liquid fuel cannot be premixed unless the fuel has previously been
evaporated (pre-evaporated).
[0007] In a case of liquid fuel, fuel to be injected is atomized
when the fuel passes through nozzles having a small passage
cross-section. Usually, droplets of the fuel remain at the time of
ignition. Since combustion occurs while the droplets are being
evaporated, a location with a theoretical air ratio is inevitably
produced, and temperature locally increases. Thus, there is a limit
to reduction of thermal NOx.
[0008] Pre-evaporation has been known as technology to solve the
above problems. In pre-evaporation, a pre-evaporation portion is
provided inside or outside of a combustor, and fuel is sprayed into
the pre-evaporation portion, evaporated by heating from an external
source, and then combusted. According to the pre-evaporation,
thermal NOx reduction equivalent to that in the case of gaseous
fuel can be expected. However, the size of the combustion apparatus
problematically becomes large by the pre-evaporation portion.
[0009] Further, fuel or air is divided into several stages and
supplied into a combustion apparatus so that air ratios are
controlled at each region in a combustion chamber. In this case, a
portion having a fuel concentration higher than a theoretical air
ratio and a portion having a fuel concentration lower than the
theoretical air ratio are intentionally formed so as to avoid a
mixed state region with the theoretical air ratio, thereby reducing
thermal NOx.
[0010] However, such technology has been employed in many
large-sized combustion furnaces but cannot be applied to
small-sized combustion apparatuses because a supply system of fuel
or air becomes complicated. Further, it is difficult to find
optimal supply locations of fuel or air and optimal division
ratios, or to control these locations and division ratios according
to loads.
[0011] Burnt gas recirculation is technology to achieve slow and
uniform combustion by mixing a combustion gas having a high
temperature and a low oxygen concentration with combustion air.
Thus, a combustion temperature is lowered while an inert gas is
increased so as to increase a heat capacity. An average flame
temperature is lowered. Hence, thermal NOx is reduced. The burnt
gas recirculation is applied mainly to a combustion apparatus in a
boiler and an industrial furnace, and an engine.
[0012] Methods to produce burnt gas recirculation include use of a
flame holder, external recirculation, and internal recirculation.
Combustion methods called flue gas recirculation (FGR) or exhaust
gas recirculation (EGR) have been known but are basically the same
technology as the burnt gas recirculation.
[0013] For example, Japanese laid-open patent publication No.
2002-364812 discloses an example using burnt gas recirculation for
gaseous fuel. Japanese patent No. 3139978 discloses an example
using burnt gas recirculation for premixed combustion of gaseous
fuel. In either case, a combustion gas is recirculated in a
recirculation region formed centrally downstream of a flame holding
plate and in a space between a combustion apparatus projecting in a
combustion chamber and a combustion chamber wall.
[0014] However, a burnt gas recirculation flow centrally downstream
of the flame holding plate does not reach a portion in which fuel
is mixed with air before ignition. The burnt gas recirculation flow
serves merely to stabilize ignition. Actually, a burnt gas
recirculation flow from the space between the combustion apparatus
and the combustion chamber wall is circulated only near the
combustion apparatus. Accordingly, a combustion gas that has been
sufficiently combusted so as to have a high temperature and a low
oxygen concentration is not recirculated, and the amount of
circulation is small. Thus, reduction effect of thermal NOx becomes
small.
[0015] Further, in these combustion apparatuses the size of the
combustion chamber must be sufficiently larger than the diameter of
the combustion apparatus in order to draw a burnt gas recirculation
flow from the outside of the combustion apparatus in a direction of
a central axis. Accordingly, this technology is not suited for
purposes where the size of a combustion chamber of a combustion
apparatus of a gas turbine or the like should be made as small as
possible. Further, it is difficult to apply this technology to
liquid fuel.
[0016] For example, Japanese laid-open patent publication No.
9-133310 discloses technology regarding gaseous fuel to recirculate
a combustion gas from a rear central portion of a flame holding
plate by the flame holding plate, produce a lifted and divided
flame, and recirculate a combustion gas from a lateral portion of
the flame. According to this technology, the amount of burnt gas
recirculation can be increased. However, a structure of a burner
becomes complicated due to the divided flame. A cross-section of
the burner includes a portion having no flame. Accordingly, the
size of the burner problematically becomes large (a combustion load
per volume is low). Further, it is difficult to apply this
technology to liquid fuel.
[0017] For example, in a combustion apparatus using premixed
combustion of gaseous fuel for a boiler disclosed in Japanese
laid-open patent publication 11-153306, a plurality of premixed gas
injection holes are provided in a combustion chamber wall, and a
premixed gas is injected as a combustion gas toward an adjacent
premixed gas injection hole. However, since fuel and air have
previously been mixed, fresh air is involved in combustion at the
time of ignition and mixed with a combustion gas only after
starting combustion. Accordingly, there is a problem that effect to
make combustion slow is small. Further, this technology relates to
premixed combustion for gaseous fuel. A premixed gas reaches a next
injection hole in a short period of time. It is difficult to apply
this technology to liquid fuel.
[0018] For example, in a burner for a boiler disclosed in Japanese
patent No. 3171147, a low-pressure portion is formed by kinetic
energy of combustion air flowing around a fuel nozzle, mainly with
respect to liquid fuel. A combustion gas in a furnace is drawn and
mixed with the combustion air. However, since the combustion gas is
mixed outside of the combustion air, the combustion gas is hardly
mixed inside of the combustion air. Fuel is first mixed with the
combustion air and then gradually mixed with the combustion gas.
Accordingly, a combustion phenomenon depends on combustion air
having the same oxygen concentration as usual, and hence slow
ignition and combustion under a low oxygen concentration cannot be
achieved sufficiently. Further, a structure for drawing a
combustion gas is complicated. Furthermore, since a divided flame
is employed, the burner has a complicated structure. A
cross-section of the burner includes a portion having no flame.
Accordingly, the size of the burner problematically becomes large
(a combustion load per volume is low).
[0019] For example, Japanese patent publication No. 2000-79837
discloses technology in which a swirling flow is induced in a
cylindrical combustion apparatus so that static pressure is lowered
at a central portion of the swirling flow to thereby draw another
gas from a normal direction of a swirling surface into a swirling
center. This technology is applied to burnt gas recirculation at a
secondary combustion zone in a cylindrical combustion apparatus.
Not only supply of primary air and secondary air for combustion,
but also supply of fuel serve to induce a swirling flow. However,
effect of recirculation of the combustion gas introduced by the
swirling flow is limited to combustion control at a secondary
combustion zone. A region of a high fuel concentration near a flame
is not a targeted region of the burnt gas recirculation.
Accordingly, NOx reduction effect is limited only to temperature
control at an end portion of flame.
[0020] Next, a specific arrangement of a conventional combustion
apparatus and problems of the conventional combustion apparatus
will be described in greater detail with reference to FIGS. 1
through 4.
[0021] FIG. 1 shows an example of a conventional general combustion
apparatus. The combustion apparatus shown in FIG. 1 is a
cylindrical combustion apparatus and has a cylindrical container
2001, an inflow casing 2002, a partition cylinder 2004, a fuel
nozzle 2005, and a flame holding plate 2006 disposed downstream of
the fuel nozzle 2005 and coaxially with the fuel nozzle 2005.
Inflow passages are formed by the cylindrical container 2001, the
inflow casing 2002, and the partition cylinder 2004.
[0022] Combustion air 2010 flows into the inflow casing 2002, flows
through a space 2012 between the partition cylinder 2004 and the
fuel nozzle 2005, and then flows near the flame holding plate 2006
into the cylindrical container 2001 by a blower or a compressor
(not shown).
[0023] On the other hand, fuel 2014 is injected through the fuel
nozzle 2005 into the cylindrical container 2001 by a fuel pump, a
blower, or a compressor (not shown). The fuel 2014 is mixed with
the combustion air 2010 and combusted to produce a combustion gas
2016. The produced combustion gas 2016 flows out of an open end
2007 of the cylindrical container 2001.
[0024] Here, the flame holding plate 2006 allows stable ignition.
In the example shown in FIG. 1, the flame holding plate 2006 is in
the form of a cone having a larger diameter near the open end 2007.
The flame holding plate 2006 blocks a flow of air flowing through
the space 2012 between the partition cylinder 2004 and the fuel
nozzle 2005, reduces a velocity of flow of the combustion air 2010
at a tip of the fuel nozzle 2005, and forms a flow region 2018, in
which air flows backward from a downstream region, at a downstream
side of the flame holding plate 2006. The back flow 2018 returns a
combustion gas 2016 having a high temperature to an ignition region
right downstream of the tip of the fuel nozzle 2005.
[0025] However, the back flow of the combustion gas is present only
at an inner side 2020 of a fuel track 2014 but does not reach a
portion at which the fuel 2014 is mixed with the air 2010.
Accordingly, a unction of the back flow of the combustion gas is
merely to stabilize ignition.
[0026] An example of an annular combustion apparatus to which the
combustion apparatus shown in FIG. 1 is directly applied will be
described with reference to FIGS. 2A and 2B. As described above, in
the case of the cylindrical combustion apparatus shown in FIG. 1,
the flame holding plate 2006 is in the form of a cone. However, in
the case of the annular combustion apparatus shown in FIGS. 2A and
2B, an annular flame holding plate 2006a is employed as shown in
FIG. 2B.
[0027] As shown in FIG. 2B, a plurality of cylindrical fuel nozzles
2005 may be attached to the flame holding plate 2006a. An annular
fuel nozzle (not shown) may be employed. Effects of the fuel
nozzles 2005 are the same as those in the case of the cylindrical
combustion apparatus shown in FIG. 1.
[0028] An arrangement, effects, and problems of a conventional
combustion apparatus which utilizes burnt gas recirculation will be
described with reference to FIG. 3. A combustion apparatus shown in
FIG. 3 is a cylindrical combustion apparatus, which is applied to
boilers or industrial furnaces. The combustion apparatus has a
first swirler 2003 through which combustion air 2010 passes, a
second swirler 2030 disposed outside of an annular container 2001,
and an outer cylinder 2031 in addition to the arrangement of the
conventional combustion apparatus shown in FIG. 1
[0029] The swirler 2003 swirls a flow of the combustion air 2010 to
form a negative pressure region at the center of the swirling flow
so as to form a flow region 2019 in which the air flows back from a
downstream side of the flow region 2019. The back flow 2019 returns
a combustion gas 2016 having a high temperature to an ignition
region right downstream of the tip of the fuel nozzle 2005. Thus,
the swirler 2003 stabilizes ignition as with the flame holding
plate 2006.
[0030] When the second swirler 2030 is located away from a
combustion chamber wall 2032, the combustion gas 2016 in a
combustion chamber is drawn through the second swirler 2030 by
induction effect of the flowing combustion air 2010, mixed with the
combustion air 2010, and combusted.
[0031] This is a typical example of conventional technology which
utilizes burnt gas recirculation. Since the combustion gas 2016 is
introduced from an outside of the swirling flow of the combustion
air 2010, the combustion gas 2016 is hardly mixed inside of the
combustion air 2010. The fuel 2014 is first mixed with the
combustion air 2010 and gradually mixed with the combustion gas
2016. Accordingly, combustion phenomenon depends on the combustion
air 2010 having the same oxygen concentration as usual, and hence
ignition and combustion under a low oxygen concentration cannot be
achieved.
[0032] Further, in the combustion apparatus shown in FIG. 3, since
a burnt gas recirculation flow is drawn from an outside of the
outer cylinder 2031, the size of the combustion chamber must be
sufficiently larger than the diameter of the outer cylinder 2031.
Accordingly, this combustion apparatus is not suited for purposes
of a combustion apparatus of a gas turbine or the like where the
size of the combustion chamber should be made as small as possible.
Furthermore, the combustion apparatus shown in FIG. 3 is not suited
for application to an annular combustion apparatus.
[0033] An arrangement, effects, and problems of a conventional
annular gas turbine combustion apparatus will be described with
reference to FIG. 4. A conventional combustion apparatus of a gas
turbine has a extremely low total air ratio because a targeted
temperature is considerably lower than a flame temperature in
combustion with a theoretical amount of air, i.e., just the amount
of air containing oxygen required for combustion of fuel. When
general hydrocarbon fuel is used, it is difficult to combust the
fuel by a single stage with such total air ratio.
[0034] For this reason, supply of the combustion air is divided
into several stages. First, fuel is mixed with only a portion of
the combustion air (primary air 2040) and combusted. Then, the rest
of the combustion air is added. Thus, complete combustion is
achieved under a desired outlet temperature.
[0035] A region from a location at which combustion air of the
first stage is mixed with fuel in the container 2001a to air inflow
portions of the second stage is referred to as a primary combustion
zone 2042. With regard to combustion in a gas turbine, many
technical ideas to add air downstream of the primary combustion
zone 2042 have been known to prevent a lowered combustion
efficiency, discharge of unburnt components, and increase of
NOx.
[0036] In FIG. 4, the reference numeral 2044 represents air holes
formed in the container 2001a, and the reference numeral 2046
represents secondary and dilution air flowing from the air holes
2044 into the container 2001a.
[0037] As described above, combustion under a low oxygen
concentration by burnt gas recirculation has been known as an
effective method for reducing thermal NOx. However, there are no
conventional combustion apparatuses, directed to combustion under a
low oxygen concentration by burnt gas recirculation, which have a
sufficient amount of burnt gas recirculation or NOx reduction
effects and there are no conventional combustion apparatuses which
can achieve pre-evaporation combustion even with liquid fuel and
premixed combustion as with gaseous fuel.
DISCLOSURE OF INVENTION
[0038] The present invention has been proposed in view of the above
drawbacks of the conventional technology. It is, therefore, an
object of the present invention to provide a combustion apparatus
which has a relatively simple structure, can maximize effects of
burnt gas recirculation, can achieve pre-evaporation in a case of
liquid fuel, premixed combustion in a case of gaseous fuel/liquid
fuel, and slow combustion under a low oxygen concentration, and can
suppress generation of NOx.
[0039] Further, another object of the present invention is to
provide a combustion apparatus suitable for inexpensively achieving
use of ceramics to improve high-temperature resistance,
particularly a combustion apparatus which can simplify a structure
and reduce cost when applied to a gas turbine combustion
apparatus.
[0040] According to a first aspect of the present invention, there
is provided a combustion apparatus which can positively control and
generate burnt gas recirculation with a simple structure. The
combustion apparatus has an annular container having an inner
cylindrical portion forming an inner circumferential side surface,
an outer cylindrical portion forming an outer circumferential side
surface, an open end, and a close end; an air supply portion for
supplying combustion air into the annular container so as to have a
velocity component in a direction of a central axis of the annular
container from the open end to the close end of the annular
container and a fuel supply portion for supplying fuel into the
annular container so as to have a velocity component in the
direction of the central axis of the annular container from the
close end to the open end of the annular container. A flow of the
combustion air supplied into the annular container first crosses a
track of the fuel at a region away from the fuel supply portion and
then crosses the track of the fuel again at a region near the fuel
supply portion.
[0041] According to the present invention, the combustion apparatus
has a combustion chamber having an annular cross-section and is
configured so that a flow of the supplied air first crosses a track
of the supplied fuel at a region away from the fuel supply means
and then crosses a track of the supplied fuel again at a region
near the fuel supply means. Accordingly, it is possible to
positively generate burnt gas recirculation with a simple
structure. Thus, when the present invention is applied to a general
combustion apparatus, it is possible to enhance the stability and
maximize effects of burnt gas recirculation.
[0042] Since effects of burnt gas recirculation can be maximized
with high stability, it is possible to perform combustion with a
combustion gas having a high temperature and a low oxygen
concentration. Accordingly, it is possible to achieve
pre-evaporation combustion having stable evaporation
characteristics in a case of liquid fuel, in which it has been
difficult to reduce NOx with the conventional technology, premixed
combustion in either case of gaseous fuel or liquid fuel, slow
combustion, uniform combustion with a low maximum flame
temperature, and combustion with a low average flame temperature
due to the heat capacity of an inert gas in the combustion gas.
Therefore, it is possible to suppress thermal NOx, which has been
difficult to suppress with the conventional technology.
[0043] Here, in the combustion chamber having an annular
cross-section, the track of the air and the track of the fuel are
not the same, and the track of the air and the track of the fuel
intersect each other two times. The track of the air flow first
crosses a track of the fuel flow near a tip of the fuel track and
then crosses the track of the fuel flow again at a region from a
root of the track of the fuel flow to the vicinity of the tip. In
order to meet the above requirements, for example, the air flow and
the fuel flow are opposed in a state such that the air flows in an
opposite direction of the outlet direction while the fuel flows in
the outlet direction, and the fuel spreads outwardly in a direction
perpendicular to the central axis of the combustion chamber
(outwardly in a radial direction in a case of a cylindrical
container) as the fuel is farther from an injection side.
[0044] According to a second aspect of the present invention, there
is provided a combustion apparatus which can positively control and
generate burnt gas recirculation with a simple structure. The
combustion apparatus has an annular container having an inner
cylindrical portion forming an inner circumferential side surface,
an outer cylindrical portion forming an outer circumferential side
surface, an open end, and a close end; an inflow passage for
supplying combustion air into the annular container, the inflow
passage being formed at a location away from the close end in a
direction of a central axis of the annular container so as to
extend through the outer circumferential side surface of the
annular container; and a fuel nozzle provided inside of the close
end of the annular container for supplying fuel into the annular
container. The inflow passage is configured so as to form a flow of
the air with a velocity component in the direction of the central
axis of the annular container from the open end to the close end
and a velocity component to swirl in a circumferential direction of
the annular container. The fuel nozzle is configured so as to
inject the fuel toward the inflow passage with a velocity component
in the direction of the central axis of the annular container from
the close end to the open end and a velocity component directed
radially outward.
[0045] According to a third aspect of the present invention, there
is provided a combustion apparatus which can positively control and
generate burnt gas recirculation with a simple structure. The
combustion apparatus has an annular container having an inner
cylindrical portion forming an inner circumferential side surface,
an outer cylindrical portion forming an outer circumferential side
surface, an open end, and a close end; an inflow passage for
supplying combustion air into the annular container; and a fuel
nozzle for supplying fuel into the annular container. The outer
cylindrical portion has a portion having a reduced diameter at a
location away from the close end along a central axis of the
annular container by a predetermined distance. The inflow passage
is formed at the portion having a reduced diameter in the outer
cylindrical portion and is configured so as to form a flow of the
air with a velocity component in the direction of the central axis
of the annular container from the open end to the close end and a
velocity component to swirl in a circumferential direction of the
annular container. The fuel nozzle is configured so as to inject
the fuel toward the inflow passage with a velocity component in the
direction of the central axis of the annular container from the
close end to the open end and a velocity component directed
radially outward.
[0046] According to a fourth aspect of the present invention, there
is provided a combustion apparatus which can positively control and
generate burnt gas recirculation with a simple structure. The
combustion apparatus has an annular container having an inner
cylindrical portion forming an inner circumferential side surface,
an outer cylindrical portion forming an outer circumferential side
surface, an open end, and a close end; a cylindrical member
disposed substantially coaxially with a central axis of the annular
container and positioned on the open end side of said outer
cylindrical portion, the cylindrical member having a diameter
smaller than that of the outer cylindrical portion; an annular
connecting member connecting an end of the outer cylindrical
portion and an outer circumferential surface of the cylindrical
member to each other; an inflow passage formed in the connecting
member for supplying combustion air into the annular container; and
a fuel nozzle provided inside of the close end of the annular
container for supplying fuel into the annular container. The inflow
passage is configured so as to form a flow of the air with a
velocity component in the direction of the central axis of the
annular container from the open end to the close end and a velocity
component to swirl in a circumferential direction of the annular
container. The fuel nozzle is configured so as to inject the fuel
toward the inflow passage with a velocity component in the
direction of the central axis of the annular container from the
close end to the open end and a velocity component directed
radially outward.
[0047] According to a fifth aspect of the present invention, there
is provided a combustion apparatus which can positively control and
generate burnt gas recirculation with a simple structure. The
combustion apparatus has an annular container having an inner
cylindrical portion forming an inner circumferential side surface,
an outer cylindrical portion forming an outer circumferential side
surface, an open end, and a close end; an annular member disposed
substantially coaxially with a central axis of the annular
container and positioned on the open end side, the annular member
having an inner cylindrical portion forming an inner
circumferential side surface and an outer cylindrical portion
forming an outer circumferential side surface and having a diameter
smaller than that of the outer cylindrical portion of the annular
container; a first connecting member connecting an end surface, on
the open end side, of the outer cylindrical portion of the annular
container and an outer circumferential surface of the outer
cylindrical portion of the annular member to each other; a second
connecting member connecting an end surface, on the open end side,
of the inner cylindrical portion of the annular container and an
end surface of the inner cylindrical portion of the annular member
to each other; an inflow passage formed in the first connecting
member for supplying combustion air into the annular container; and
a fuel nozzle provided inside of the close end of the annular
container for supplying fuel into the annular container. The inflow
passage is configured so as to form a flow of the air with a
velocity component in the direction of the central axis of the
annular container from the open end to the close end and a velocity
component to swirl in a circumferential direction of the annular
container. The fuel nozzle is configured so as to inject the fuel
toward the inflow passage with a velocity component in the
direction of the central axis of the annular container from the
close end to the open end and a velocity component directed
radially outward.
[0048] An additional inflow passage may be provided in the inner
cylindrical portion of the annular container for supplying air into
the annular container. An additional inflow passage (auxiliary air
inflow port) may be provided on the close end at a location near
the inner cylindrical portion of the annular container and may be
positioned radially inward from the fuel nozzle so that air flows
in the direction of the central axis of the annular container. An
additional inflow passage may be provided in the outer cylindrical
portion of the annular container for supplying air inwardly in a
radial direction of the annular container. The combustion apparatus
may further have a flow adjusting structure disposed on the close
end within the annular container and/or on the outer cylindrical
portion of the annular container near the close end for suppressing
a swirling flow of the air near the close end.
[0049] The combustion apparatus may further have a flow adjusting
structure (guide vane) disposed on the close end within the annular
container and/or on the outer cylindrical portion of the annular
container near the close end for converting a flow of air having a
velocity component in a direction of the central axis of the
annular container from the open end to the close end and swirling
in a circumferential direction of the annular container into a flow
directed inwardly in a radial direction of the annular container
near the close end.
[0050] An additional fuel nozzle may be provided at a location
closer to the close end than the inflow passage with respect to the
direction of the central axis of the outer cylindrical portion of
the annular container.
[0051] According to the present invention, the fuel flow has a
velocity component in the direction of the central axis of the
combustion chamber and a velocity component directed from the
central axis of the combustion chamber toward a wall surface of the
combustion chamber i.e., a velocity component directed radially
outward. The air flow has a velocity component in an opposite
direction of the central axis of the combustion chamber and a
velocity component to swirl in a circumferential direction. The
flow of the fuel has a velocity component in the direction of the
outlet of the combustion apparatus, and the flow of the combustion
air has a velocity component in an opposite direction to the
direction of the outlet. Accordingly, the aforementioned flows can
be achieved.
[0052] According to the present invention, a portion of the flow of
the air supplied from the air supply means (inflow passage) into
the combustion chamber flows as a combustion gas having a low
temperature or an air flow not being a combustion gas along an
inner wall surface of the combustion chamber. As a result, the
inner wall of the combustion apparatus is protected from heat in
the combustion apparatus by the combustion gas having a low
temperature or the air flow not being a combustion gas.
Consequently, it is possible to provide a combustion apparatus
having a high durability to combustion heat.
[0053] As described above, according to the present invention, it
is possible to provide a simple structure which can positively
control and generate burnt gas recirculation. Accordingly, it is
possible to provide a combustion apparatus which can readily use a
heat resistant material such as ceramics, can facilitate
disassembly and part replacement, and has easiness of
maintenance.
[0054] When an auxiliary fuel nozzle is provided, it is possible to
provide a combustion apparatus which can suppress generation of
thermal NOx in combustion with multi fuel of gaseous fuel/liquid
fuel and combustion with fuel having a low heating value or a waste
liquid.
[0055] When the present invention having the above arrangement is
applied to a primary combustion zone of a gas turbine combustion
apparatus, it is possible to positively generate burnt gas
recirculation with a simple structure. Thus, the stability can be
enhanced in the primary combustion zone of the gas turbine
combustion apparatus and effects of burnt gas recirculation can be
maximized.
[0056] In the gas turbine combustion apparatus to which the present
invention is applied, the primary combustion zone can be designed
to be leaner because of high stability. Accordingly, it is possible
to lower an average combustion temperature so as to further
suppress generation of thermal NOx.
[0057] Further, in the gas turbine combustion apparatus to which
the combustion apparatus of the present invention is applied, it is
possible to enhance the stability and maximize effects of burnt gas
recirculation. Accordingly, it is possible to suppress generation
of thermal NOx in a case of liquid fuel, in which it has been
difficult to reduce NOx with the conventional technology.
[0058] As described above, in the combustion apparatus of the
present invention, since an inner wall of the combustion apparatus
is suitably cooled by an air flow having a low temperature, it is
possible to provide a gas turbine combustion apparatus having a
high durability.
[0059] Further, in the combustion apparatus of the present
invention, because of a simple structure, it is possible to provide
a gas turbine combustion apparatus which can readily use a heat
resistant material such as ceramics, facilitate disassembly and
replacement, and has easiness of maintenance.
[0060] Additionally, in a gas turbine to which a combustion
apparatus of the present invention is applied, since a liner can be
exposed while no air flows outside of the primary combustion zone,
a fuel nozzle and an ignition device can be disposed with a simple
structure, so that cost can be reduced.
[0061] Additionally, since thermal expansion of the liner can be
reduced with respect to the casing, the structure can be
simplified. Accordingly, it is possible to further reduce cost.
[0062] When a gas turbine is formed by a combustion apparatus
having an auxiliary fuel nozzle, it is possible to suppress
generation of thermal NOx in multi fuel combustion of gaseous
fuel/liquid fuel and combustion with fuel having a low heating
value or a waste liquid.
BRIEF DESCRIPTION OF DRAWINGS
[0063] FIG. 1 is a cross-sectional view showing a conventional
cylindrical combustion apparatus;
[0064] FIG. 2A is a cross-sectional view showing a conventional
annular combustion apparatus;
[0065] FIG. 2B is a front view of FIG. 2A;
[0066] FIG. 3 is a cross-sectional view showing another example of
a conventional cylindrical combustion apparatus;
[0067] FIG. 4 is a cross-sectional view showing a conventional
annular combustion apparatus for a gas turbine;
[0068] FIG. 5 is a perspective view showing a combustion apparatus
according to a first embodiment of the present invention;
[0069] FIG. 6 is a cross-sectional view of FIG. 5;
[0070] FIG. 7 is a perspective view showing a combustion apparatus
according to a second embodiment of the present invention;
[0071] FIG. 8 is a cross-sectional view of FIG. 7;
[0072] FIG. 9 is a perspective view showing a combustion apparatus
according to a third embodiment of the present invention;
[0073] FIG. 10 is a cross-sectional view of FIG. 9;
[0074] FIG. 11 is a perspective view showing a combustion apparatus
according to a fourth embodiment of the present invention;
[0075] FIG. 12 is a cross-sectional view of FIG. 11;
[0076] FIG. 13 is a perspective view showing an example of a
swirler in the embodiments of the present invention;
[0077] FIG. 14 is a perspective view showing another example of a
swirler in the embodiments of the present invention;
[0078] FIG. 15 is a perspective view showing another example of a
swirler in the embodiments of the present invention;
[0079] FIG. 16 is a cross-sectional view showing another example of
an inflow casing in the embodiments of the present invention;
[0080] FIG. 17 is a perspective view showing another example of an
inflow casing in the embodiments of the present invention;
[0081] FIG. 18 is a cross-sectional view of FIG. 17;
[0082] FIG. 19 is a perspective view showing another example of a
fuel nozzle in the embodiments of the present invention;
[0083] FIG. 20 is a cross-sectional view of FIG. 19;
[0084] FIG. 21 is a perspective view showing an effect of the
embodiments of the present invention;
[0085] FIG. 22A is a partial enlarged cross-sectional view of FIG.
21;
[0086] FIG. 22B is an enlarged view of FIG. 22A;
[0087] FIG. 23 is a cross-sectional view showing a combustion
apparatus according to a fifth embodiment of the present
invention;
[0088] FIG. 24 is a cross-sectional view showing a combustion
apparatus according to a sixth embodiment of the present
invention;
[0089] FIG. 25 is a perspective view showing a combustion apparatus
according to a seventh embodiment of the present invention;
[0090] FIG. 26 is a perspective view showing a combustion apparatus
according to an eighth embodiment of the present invention;
[0091] FIG. 27 is a perspective view showing a combustion apparatus
according to a ninth embodiment of the present invention;
[0092] FIG. 28 is a perspective view showing a combustion apparatus
according to a tenth embodiment of the present invention;
[0093] FIG. 29 is a perspective view showing a combustion apparatus
according to an eleventh embodiment of the present invention;
[0094] FIG. 30 is a perspective view showing a combustion apparatus
according to a twelfth embodiment of the present invention;
[0095] FIG. 31 is a cross-sectional view showing a combustion
apparatus according to a thirteenth embodiment of the present
invention;
[0096] FIG. 32 is a perspective view showing a combustion apparatus
according to a fourteenth embodiment of the present invention;
[0097] FIG. 33 is a cross-sectional view of FIG. 32;
[0098] FIG. 34 is a cross-sectional view showing a combustion
apparatus according to a fifteenth embodiment of the present
invention;
[0099] FIG. 35 is a cross-sectional view showing a combustion
apparatus according to a sixteenth embodiment of the present
invention;
[0100] FIG. 36 is a perspective view showing a case where a swirler
is not used in the combustion apparatus of the second embodiment of
the present invention;
[0101] FIG. 37 is a cross-sectional view of FIG. 36; and
[0102] FIG. 38 is a block diagram showing a case where a combustion
apparatus according to the present invention is applied to a gas
turbine generator.
BEST MODE FOR CARRYING OUT THE INVENTION
[0103] A combustion apparatus according to embodiments of the
present invention will be described below with reference to FIGS. 5
through 38. In the following embodiments, the same parts are
denoted by the same reference numerals and will not be described
below repetitively.
[0104] First, a combustion apparatus according to a first
embodiment will be described with reference to FIGS. 5 and 6. The
combustion apparatus shown in FIG. 5 has an annular container 12
with one end (close end) 10 which is closed, an inflow casing 14, a
swirler 16, and a fuel nozzle 18 provided on a rear face of the
upper end (close end) 10 of the annular container 12. A plurality
of air inflow portions 20 are formed at common pitches on a side
surface of a peripheral portion (outer cylindrical portion 13
described below) of the annular container 12. Combustion air 22
flows through the air inflow portions 20 into the interior of the
annular container 12, and inflow passages are formed by the air
inflow portions 20, the inflow casing 14, and the swirler 16.
[0105] As shown in FIG. 6 in detail, the annular container 12 has
an inner cylindrical portion 15 and an outer cylindrical portion
13, and is configured such that the inner cylindrical portion 15
and the outer cylindrical portion 13 are closed by the close end
10. A lower end of the annular container 12 serves as an opened
outlet 26 for a combustion gas. A plurality of inner air inflow
portions 30 are formed in the inner cylindrical portion 15 of the
annular container 12 at positions above the air inflow portions 20
formed in the outer cylindrical portion 13.
[0106] The swirler 16 has guide vanes, which are not explicitly
illustrated in FIGS. 5 and 6. For example, the same number of guide
vanes as a plurality of air inflow portions 20 at the common
pitches are disposed so as to twist and extend upward in oblique
directions, not in normal directions with respect to a central
axis. Inner ends of the guide vanes are connected to the vicinities
of the air inflow portions 20. Other details of the swirler 16 will
be described later.
[0107] The inflow casing 14 has an inner cylinder 34 disposed so as
to form a predetermined gap portion 32 inside of the inner
cylindrical portion 15 of the annular container 12, an outer
cylinder 38 disposed so as to form a predetermined gap portion 36
outside of the outer cylindrical portion 13 of the annular
container 12, an inner bottom member 40 connecting a lower end of
the inner cylinder 34 to a lower end of the inner cylindrical
portion 15 of the annular container 12, and an outer bottom member
42 connecting a lower end of the outer cylinder 38 to a lower end
of the outer cylindrical portion 13 of the annular container
12.
[0108] Although the fuel nozzle 18 is not explicitly illustrated in
FIGS. 5 and 6, for example, the fuel nozzle 18 can be provided by
forming a large number of holes (nozzle holes) in a single hollow
ring, or by attaching a large number of nozzle tips.
[0109] In the combustion apparatus thus constructed, combustion air
22 flows into the gap 36, which is formed by the outer cylinder 38
of the inflow casing 14 and the outer cylindrical portion 13 of the
annular container 12, and then flows through the swirler 16 from
the air inflow portions 20 into the annular container 12 upward in
oblique directions by a blower or a compressor (not shown). Fuel 21
is injected through the fuel nozzle 18 into the interior of the
annular container 12 by a fuel pump, a blower, or a compressor (not
shown). The fuel 21 and the combustion air 22 are mixed and
combusted in the annular container 12, and a combustion gas 24 is
discharged from the open end 26 of the annular container 12.
[0110] In the first embodiment, as shown in FIG. 6, the combustion
air 22 flows into the annular container 12 (upward in oblique
directions from the air inflow portions 20) from positions which
are located away from the close end 10 of the annular container 12
in an axial direction of the annular container 12 by a
predetermined distance with a velocity component in a direction
opposite to a direction from the close end 10 to the open end 26 of
the annular container 12 (outlet direction), and swirls in the
annular container 12. Specifically, the air 22 flowing from the air
inflow portions 20 into the annular container 12 forms a flow 28
having a velocity component in the direction of the central axis J
of the annular container 12 from the open end 26 to the close end
10 and a velocity component to swirl in a circumferential direction
of the annular container 12.
[0111] Simultaneously, fuel 23 is injected toward the inflow
portions 20 for the combustion air in a direction from the close
end 10 to the outlet 26 of the annular container 12 with a
divergence angle .alpha. with respect to the central axis of the
annular container 12 in a radial direction. Specifically, the fuel
23 is injected toward the air inflow portions 20 (inflow passages)
with a velocity component in the direction of the central axis J
from the close end 10 to the open end 26 and a velocity component
directed radially outward.
[0112] Further, since air 22a flows from the inner air inflow
portions 30 downward in oblique directions within the annular
container 12, an inner wall of the inner cylindrical portion 15 of
the annular container 12 is suitably cooled.
[0113] Although not shown in the drawings, an opening ratio,
shapes, and pitches of the air inflow portions 20 in the side
surface of the annular container 12 can be set arbitrarily.
Further, although not shown in the drawings, a structure to deflect
the flowing combustion air 22 may be provided on the inflow
portions 20 for the combustion air 22 flowing into the annular
container 12 as long as the flowing combustion air 22 has a
velocity component in a direction opposite to the outlet 26.
[0114] In FIG. 6, the reference numeral 28 represents a swirling
flow having a large velocity component in a direction opposite to
the outlet 26, which is formed by the combustion air 22 flowing
from the air inflow portions 20 and a combustion gas produced by
combustion of mixture of the combustion air 22 and the fuel.
[0115] Next, a combustion apparatus according to a second
embodiment will be described with reference to FIGS. 7 and 8. FIGS.
7 and 8 show an embodiment of a combustion apparatus in which the
annular container 12 in the first embodiment shown in FIGS. 5 and 6
is replaced with an annular container 112 having a structure in
which an outer cylindrical portion 113 is constricted (a stepped
structure). Air inflow portions 20 are formed at a stepped portion
100, i.e., a portion at which a diameter of the outer cylindrical
portion 113 in the annular container 112 varies
discontinuously.
[0116] A swirler 16 and an inflow casing 14 are substantially the
same as those in a fourth embodiment described later. Accordingly,
details of the swirler 16 and the inflow casing 14 will be
described in the fourth embodiment.
[0117] According to the second embodiment thus constructed,
combustion air 22 flows from the air inflow portions 20 into the
annular container 112 so as to form a swirling flow 28 having a
larger velocity component in a direction opposite to an outlet 26.
Specifically, the air 22 flowing into the annular container 112
forms a flow 28 having a velocity component in a direction of a
central axis J of the annular container 112 from the open end 26 to
a close end 110 and a velocity component to swirl in a
circumferential direction.
[0118] Simultaneously, fuel 23 is injected toward the air inflow
portions 20 (inflow passages) with a velocity component in the
direction of the central axis J from the close end 10 to the open
end 26 and a velocity component directed radially outward.
[0119] In FIGS. 7 and 8, the cross-section change portion 100 of
the outer cylindrical portion 113 in the annular container 112 is
illustrated as being perpendicular to the axial direction of the
annular container 112. However, the cross-section change portion
100 can have any desired angle. Further, although not shown in the
drawings, an opening ratio, shapes, and pitches of the air inflow
portions 20 can be set arbitrarily. Furthermore, although not shown
in the drawings, a structure to deflect the flowing combustion air
22 may be provided on the air inflow portions 20. In FIG. 8, the
reference numeral 115 represents an inner cylinder of the annular
container 112, and the reference numeral 110 represents a close end
of the annular container 112.
[0120] Next, a combustion apparatus according to a third embodiment
of the present invention will be described with reference to FIGS.
9 and 10. FIGS. 9 and 10 show an embodiment of a combustion
apparatus in which the annular container 112 in the second
embodiment shown in FIGS. 7 and 8 is replaced with the following
annular container 212 according to manufacturing requirements. In
the annular container 212, an inner circumferential side surface
(inner cylindrical portion) 215 of the annular container 212 is
extended downstream at a cross-section change portion (stepped
portion), and a secondary cylinder 200 (cylindrical member) is
separately provided.
[0121] As is apparent from FIG. 10, the secondary cylinder 200 is
small so that it can completely be received in an outer cylindrical
portion 213 of the annular container 212. Specifically, the
secondary cylinder 200 has a cross-sectional area smaller than that
of the outer cylindrical portion 213 of the annular container 212.
Thus, the secondary cylinder 200 is completely received within a
virtual cylindrical shape that is an extension of the outer
cylindrical portion 213.
[0122] An end portion 213a of the outer cylindrical portion 213 in
the annular container 212 at the side of an open end 26 is
connected to an outer circumferential surface of the secondary
cylinder 200 at the side of a close end 210 by an annular
connecting member 270. Air inflow portions 20 (inflow passages) are
formed in the connecting member 270. On the other hand, the inner
cylindrical portion 215 of the annular container 212 has a shape
extended toward the open end 26 of the annular container 212
substantially coaxially with the secondary cylinder 200.
[0123] According to the third embodiment shown in FIGS. 9 and 10,
since a combustion chamber is formed by the annular container 212,
the secondary cylinder 200, and the connecting member 270, the
combustion apparatus can readily be assembled.
[0124] In the third embodiment, air flowing from the inflow
portions 20 into the annular container 212 forms a flow 28 having a
velocity component in a direction of a central axis J of the
annular container 212 from the open end 26 to the close end 210 and
a velocity component to swirl in a circumferential direction of the
annular container 212. Simultaneously, fuel is injected toward the
inflow portions 20 (inflow passages) with a velocity component in
the direction of the central axis J from the close end 210 to the
open end 26 and a velocity component directed radially outward.
[0125] The third embodiment shown in FIGS. 9 and 10 is configured
so as to provide auxiliary air inflow ports 271 (additional inflow
passage) on an inner side of the close end 210 near the inner
cylindrical portion 215 and inwardly in a radial direction of a
fuel nozzle 18, particularly as shown in FIG. 10, to allow air to
flow in the direction of the central axis J of the annular
container 212 (as shown by arrows 272). With this arrangement, the
air 272 flows along an inner wall surface 215a of the inner
cylindrical portion 215 to efficiently cool the inner wall surface
215a of the inner cylindrical portion 215. In FIG. 9, the auxiliary
air inflow ports 271 are represented by arrows.
[0126] The auxiliary air inflow ports 271 can be applied not only
to the third embodiment shown in FIGS. 9 and 10, but also to the
first embodiment and the second embodiment shown in FIGS. 5 through
8. Similarly, an arrangement for injected air flows 271 from the
auxiliary air inflow ports 271 to cool the inner wall surface 215a
of the inner cylindrical portion can be applied to other
embodiments shown in FIGS. 11 through 38, which will be described
later.
[0127] Next, a combustion apparatus according to a fourth
embodiment will be described with reference to FIGS. 11 and 12.
FIGS. 11 and 12 show an embodiment of a combustion apparatus in
which the annular container 112 in the second embodiment shown in
FIGS. 7 and 8 is replaced with the following annular container 312
according to manufacturing requirements. In this embodiment, the
annular container 312 is divided into a secondary annular container
(annular member) 402, a first connecting member 270, and a second
connecting member 470 at a cross-section change portion (stepped
portion) 400.
[0128] In FIG. 12, the reference numeral 404 represents an inner
cylindrical portion of the secondary annular container 402, and the
reference numeral 406 represents an outer cylindrical portion of
the secondary annular container 402. As is apparent from FIG. 12,
the outer cylindrical portion 406 of the secondary annular
container 402 is small so that it can completely be received in an
outer cylindrical portion 213 of the annular container 312.
Specifically, the outer cylindrical portion 406 of the secondary
annular container 402 has a cross-sectional area smaller than that
of the outer cylindrical portion 213 of the annular container 312.
Thus, the outer cylindrical portion 406 of the secondary annular
container 402 is completely received within a virtual cylindrical
shape that is an extension of the outer cylindrical portion
213.
[0129] An end portion 213a of the outer cylindrical portion 213 in
the annular container 312 at the side of an open end 26 is
connected to an outer circumferential surface of the outer
cylindrical portion 406 of the secondary annular container 402 at
the side of a close end 210 by the first annular connecting member
270. Air inflow portions 20 (inflow passages) are formed in the
connecting member 270. On the other hand, the inner cylindrical
portion 404 of the secondary annular container 402 is located on an
extension of an inner cylindrical portion 215 of the annular
container 312. The inner cylindrical portion 404 of the secondary
annular container 402 is connected to the inner cylindrical portion
215 of the annular container 312 by the second connecting member
470.
[0130] In FIGS. 11 and 12, the inner cylindrical portion 215 of the
annular container 312 and the inner cylindrical portion 404 of the
secondary annular container 402 are illustrated as having the same
diameter. However, the diameter of the inner cylindrical portion
215 in the annular container 312 may be different from the diameter
of the inner cylindrical portion 404 in the secondary annular
container 402.
[0131] According to the fourth embodiment shown in FIGS. 11 and 12,
since a combustion chamber is formed by the annular container 312,
the secondary annular container 402, and the first connecting
member 270 and the second connecting member 470 which connect the
annular container 312 and the secondary annular container 402 to
each other, the combustion apparatus can readily be assembled.
[0132] Next, the swirler 16 will be described in detail with
reference to FIGS. 13 to 15. As shown in FIG. 13, the swirler 16 is
generally configured such that swirl vanes 54 for deflecting a flow
are disposed between the inner cylinder 50 and the outer cylinder
52 to form air introduction passages 56. Further, as shown in
another example of FIG. 14, the swirler 16 may have air
introduction passages 56a opened in an annular member 58 for
deflecting a flow. In this case, the shape of the air introduction
passages 56a may be set arbitrarily. Alternatively, as shown in
still another example of FIG. 15 which achieves the same effects as
the above swirler 16, air introduction passages 56b divided for
each air inflow portion 20 in the connecting member 270 may be
attached to the connecting member 270.
[0133] Further, in a structure shown in FIGS. 13 and 14, the
swirler 16 may also serve as a connecting member. Specifically, in
the example shown in FIG. 13, the inner cylinder 50 and the outer
cylinder 52 may be dispensed with. The secondary cylinder 200 (see
FIGS. 9 and 10) in the third embodiment and the container 212 (see
FIGS. 9 and 10) may be connected to each other by swirl vanes 54.
The secondary annular container 402 (see FIGS. 11 and 12) in the
fourth embodiment and the annular container 312 may be connected to
each other by swirl vanes 54. In either case, the swirl vanes 54
can also serve as a connecting member 270. In the example shown in
FIG. 14, the annular member 58 can also serve as a connecting
member 270 (FIGS. 9 to 12).
[0134] In FIGS. 9, 10, 11, and 12, the first connecting member 270
is illustrated as being perpendicular to the axial direction of the
annular container 312 and the secondary annular container 402.
However, the first connecting member 270 may have any desired
angle. Although not shown in the drawings, an opening ratio,
shapes, and pitches of the air inflow portions 20 can be set
arbitrarily. Furthermore, the swirler 16 is illustrated as having
an axial flow shape. However, the swirler 16 may have a mixed flow
shape in which combustion air 22 also flows from a periphery of the
swirler 16. Further, although not shown in the drawings a structure
to deflect the flowing air 22 in a radial direction may be provided
on the air inflow portions 20.
[0135] As shown in FIG. 16, the inflow casing 14 may comprise a
back flow type inflow casing 14b, which is suitable for a
centrifugal compressor and a turbine.
[0136] When an inner side of the annular container 312 (including
the annular containers 12, 112, and 212) is formed by a heat
resistant material, as shown in FIGS. 17 and 18, the inflow casing
14c may be integrated with the annular container 312 if it is not
necessary to form air inflow holes 20 in the inner side of the
annular container 312. In this case, it is not necessary to provide
a dual structure in which the inflow casing 14c encloses a portion
of the annular container 312 from the air inflow portions 20 to the
close end 210 or the entire annular container 312. Accordingly, a
fuel nozzle 18 or an ignition device, which is not shown in the
drawings, can be attached without extending through the inflow
casing 14c. Specifically, it is possible to simplify the structure
and achieve cost reduction. (In this case, it is desirable that an
exposed annular container 312 is insulated by a heat
insulator.)
[0137] With regard to the casing, although not shown in the
drawings, when the divided air introduction passages 56b as shown
in FIG. 15 serve as the swirler 16, for example, extension pipes
may be connected to the air introduction passages 56b, and an
inflow pipe to join the extension pipes may be provided instead of
the inflow casing 14. This also holds true when other air
introduction passages are provided.
[0138] With regard to the fuel nozzle, as shown in FIGS. 19 and 20,
a plurality of nozzles 18a may be disposed substantially coaxially
with each other instead of a single annular fuel nozzle 18 (FIGS. 5
through 12). This case can also achieve the same effects as a
single nozzle as long as fuel is injected from the close end 210 of
the annular container 312 toward the outlet 26 in the form of a
jet, or a cone having a relatively small divergence angle, or a
sector so as to be directed to the inflow portions 20 for the
combustion air with a radially outward angle with respect to the
central axis of the annular container 312. Particularly, a
plurality of nozzles 18a are effective in a large-sized combustion
apparatus having a difficulty in applying a single nozzle.
[0139] The aforementioned equivalent structures of the container,
the swirler, the casing, and the fuel nozzle can be applied to the
first to fourth embodiments and all of the following
embodiments.
[0140] Effects of the aforementioned embodiments will be described
in greater detail using the example of the fourth embodiment shown
in FIGS. 21, 22A, and 22B.
[0141] In FIGS. 21 and 22A, fuel 21 is injected from the fuel
nozzle 18 with a radially outward divergence angle with respect to
the central axis J (see FIG. 22A) of the annular container 312.
Specifically, the fuel 21 is injected toward the air inflow
portions 20 with a velocity component in the direction of the
central axis J from the close end 210 to the open end 26 and a
velocity component directed radially outward.
[0142] Now is considered some fuel tracks 23a and 23b (see FIG. 21)
of the fuel injected with a divergence angle with respect to the
axial direction of the annular container 312. In FIG. 22A,
combustion air 22 flows into the gap 36, which is formed by the
outer cylinder 38 of the inflow casing 14 and the outer cylindrical
portion 213 of the annular container 312, by a blower or a
compressor, which is not shown in the drawings, and then flows from
air inflow portions formed in the connecting member 270, which is
not shown in the drawings, through the swirler 16 into the annular
container 312. The combustion air 22b flowing into the annular
container 312 swirls and goes upstream in a direction opposite to
the outlet 26 within the annular container 312, and intersects one
track 23a at a location 25 (see FIG. 21). In other words, the air
22b flowing from the air inflow portions to the annular container
312 forms a flow 28 which has a velocity component in the direction
of the central axis J of the annular container 312 from the open
end 26 to the close end 210 and swirls in a circumferential
direction of the annular container 312.
[0143] In a case of liquid fuel, the diameter of particles in fuel
21 passing through the fuel track 23a becomes small at the location
25 because the fuel has been evaporated to some extent. The speed
of the fuel 21 is lower than that near an outlet of the nozzle 18
because the fuel has moved in an air flow. Because the velocities
of the fuel 21 and the combustion air 22b are opposed to each
other, the fuel 21 rides on a flow of the combustion air 22b. Thus,
the fuel 21 is ignited and combusted to form a flame.
[0144] The combustion air 22b further swirls and goes upstream in a
direction opposite to the outlet within the annular container 312
so as to become a combustion gas 24b having a high temperature and
a low oxygen concentration. As the combustion gas 24b comes close
to the close end 210 of the annular container 312, the combustion
gas 24b changes its direction so as to be close to the central axis
of the annular container 312. The combustion gas changes its
direction into a direction of the outlet 26 near the inner cylinder
215 of the annular container 312 and crosses the fuel track 23b at
a location 27. Specifically, burnt gas recirculation occurs. The
fuel track 23b crossed by the combustion gas 24a may be the same as
the fuel track 23a.
[0145] At the location 27 (see FIG. 21), the combustion gas 24b
having a high temperature and a low oxygen concentration does not
ignite the fuel but pre-evaporates the fuel. The evaporated fuel
flows together with the combustion gas 24b. Although the combustion
gas 24b has a high temperature, it has a low oxygen concentration.
Thus, the combustion gas 24b suppresses a combustion rate.
Accordingly, the evaporated fuel is not ignited immediately but is
premixed. After a certain period of time, the evaporated fuel is
ignited and combusted, and the combustion gas 24b becomes a
combustion gas 24 having a higher temperature and a lower oxygen
concentration, which is discharged from the outlet 26.
[0146] Unlike conventional technology, in the fourth embodiment, it
is important that actual ignition and combustion at a low oxygen
concentration by first bringing most of fuel into contact with the
combustion gas 24b, not first bringing most of fuel into contact
with the combustion air 22 can be achieved.
[0147] In the embodiment of the present invention as illustrated in
FIGS. 21, 22A, and 22B, if less evaporation of the fuel should be
caused near a root of the fuel track 23, more fuel is mixed with
the combustion air 22b at a tip of the fuel track 23 to increase
the temperature of the combustion gas 24b. Thus, evaporation is
promoted at the root of the fuel track 23. Specifically a feedback
effect is obtained with respect to the amount of evaporation.
Accordingly even if conditions of fuel injection are changed, the
effects according to the embodiments of the present invention (as
illustrated in FIGS. 21, 22A, and 22B) can stably be obtained.
[0148] In a case of gaseous fuel, the fuel is injected so as to
penetrate a flow of air in a jet state and reach the location 25
(before the fuel jet loses its momentum) while its peripheral
portion is partially mixed with the air. As with the case of liquid
fuel, the combustion air 22b swirls and goes upstream in a
direction opposite to the outlet 26 within the annular container
312 and intersects the fuel track 23a, so that the combustion air
22b is mixed with the fuel 21 so as to become a combustion gas 24b
having a high temperature and a low oxygen concentration.
[0149] As the combustion gas 24b comes close to the close end 210
of the annular container 312, the combustion gas 24b changes its
direction so as to be close to the central axis of the annular
container 312. The combustion gas 24b turns its direction near the
inner cylindrical portion 215 and crosses the fuel track 23b at the
location 27. Thus, burnt gas recirculation occurs. Although the
combustion gas 24b has a high temperature, it has a low oxygen
concentration. Thus, the combustion gas 24b suppresses a combustion
rate. Accordingly, the fuel is not ignited immediately but is
premixed. After a certain period of time, the fuel is ignited and
combusted.
[0150] The most fundamental effect according to the embodiments of
the present invention (as illustrated in FIGS. 21, 22A, and 22B) is
as follows. The direction of a flow of air is changed in the
combustion apparatus. The tracks of the combustion air and the fuel
are not the same in the combustion apparatus. The track of the air
and the track of the fuel intersect each other two times. Further,
the fuel and the air are mixed with each other so that the air
first intersects the fuel track near its tip and then intersects
the fuel track in a region from the root of the fuel track to the
vicinity of the tip. Thus, burnt gas recirculation is positively
controlled and generated.
[0151] In the embodiments of the present invention (as illustrated
in FIGS. 21, 22A, and 22B), a flow in the combustion apparatus is
shown in FIG. 22B within a cross-section passing through the
central axis of the annular container 312. The combustion air 22
flowing into the annular container 312 is schematically illustrated
as divided parts 22a, 22b, 22c, 22d, and 22e according to
positions.
[0152] Most 22b, 22c, and 22d of the combustion air 22 flowing into
the annular container 312 collide with the fuel track,
respectively, and thus become combustion gases 24b, 24c, and 24d.
These gases go upstream deeply within the annular container 312 and
intersect the fuel track 23 again. As an inflow position of the
combustion air is farther away from the outer cylindrical portion
213 of the annular container 312, the combustion air goes upstream
only to a shallower location and then turns its direction. Of the
combustion air 22 flowing into the annular container 312, the
combustion air 22a flowing from the location closest to an inner
surface of the outer cylinder 213 in the container 312 goes
upstream to the deepest location in the container 312 without
colliding with the fuel 21. As the combustion air 22a goes
upstream, it is mixed with the combustion gas 24b so as to become a
combustion gas 24a. Thus, the combustion gases 24a, 24b, 24c, and
24d uniformly cross the fuel track 23. Effects of the burnt gas
recirculation can be achieved most effectively.
[0153] Another fundamental effect according to the embodiments of
the present invention as illustrated in FIGS. 21, 22A, and 22B is
that the combustion gas uniformly crosses the track of the fuel.
With these effects, in the combustion apparatus according to the
embodiments of the present invention, as shown in FIG. 22A, there
are formed two flames of a second annular flame 60 near the inner
cylindrical portion 215 of the annular container 312 and a first
annular flame 62 near the outer cylindrical portion 213 but away
from an inner wall of the outer cylinder 213 of the annular
container 312.
[0154] The first annular flame 62 has a long residence time in the
annular container 312 because the combustion air 22 swirls. The
first annular flame 62 becomes uniform because it is well mixed in
the circumferential direction. An increase of temperature of the
combustion air and a reduction of oxygen concentration, which are
caused by the fact that the combustion air 22 and the fuel 21 (see
FIG. 21) are opposing each other and by the fact that a combustion
gas having a high temperature is supplied to the combustion air
that is to be mixed with the fuel from the second annular flame 60
with turbulent diffusion, promote evaporation of the fuel while
suppressing ignition of the fuel. Accordingly, the stability of the
flame is enhanced.
[0155] Further, since the combustion gases 24a, 24b, 24c, and 24d
of the first annular flame 62 cross the fuel track 23, the first
annular flame 62 serves as a reliable ignition source to enhance
the stability of the second annular flame 60. Combustion occurs
with the combustion gas having a high temperature and a low oxygen
concentration in the second annular flame 60. Accordingly,
pre-evaporation combustion, premixed combustion, and slow
combustion are achieved. Unlike usual diffusive combustion, no
areas having a theoretical mixture ratio and a high temperature are
produced locally in this combustion. The combustion is uniform with
a low maximum flame temperature. An average flame temperature is
lowered due to the heat capacity of an inert gas in the combustion
gas. Accordingly, generation of thermal NOx is suppressed.
[0156] Further, the following is advantageous in cooling. Of the
combustion air 22 flowing into the annular container 312 as shown
in FIG. 22, the combustion air 22a flowing from the location
closest to the inner circumferential surface of the outer
cylindrical portion 213 of the annular container 312 goes upstream
deepest within the annular container 312 without colliding with
(the fuel 21 or) the fuel track 23. As the combustion air goes
upstream, it is mixed with the combustion gas 24b so as to become
the combustion gas 24a. Since the combustion gas 24a has a
relatively low temperature, the inner surface of the annular
container 312 is protected from being overheated.
[0157] Meanwhile, the combustion air 22e flowing from the farthest
location away from an inner surface of the outer cylindrical
portion 213 of the annular container 312 into the annular container
312 turns at a location closer to the outlet 26 than the reaching
point of the fuel 21 and flows toward the outlet 26. Accordingly,
the combustion air 22e does not become a combustion gas but is
mixed with the combustion gas of the main flame (second annular
flame) 60 gradually from a portion away from the inner surface 406a
of the outer cylinder 406 of the secondary annular container
402.
[0158] However, the turned combustion air 22e has a relatively low
temperature at a portion closest to the inner surface 406a of the
outer cylinder 406 of the secondary annular container 402. Thus,
the inner circumferential surface 406a of the outer cylinder 406 of
the secondary annular container 402 is protected from a high
temperature of the main flame 60. The combustion gas having a high
temperature passes through surfaces of an inner side portion 215 of
the annular container 312 and an inner side (inner cylinder 404) of
the secondary annular container 402. Accordingly, air holes 30 may
be provided in the inner side portion of the annular container 312
and the inner circumferential surface 404a of the inner cylinder
404 of the secondary annular container 402, as needed, for
injecting cooling air in a jet state or along the wall surface for
cooling. When the inner side portion of the annular container 312
and the surface 404a of the inner cylinder 404 of the secondary
annular container 402 are made of a heat resistant material, no air
inflow holes 30 may be provided in the inner side portion of the
annular container 312 and the inner circumferential surface 404a of
the inner cylinder 404 of the secondary annular container 402.
[0159] The aforementioned effects in the embodiment of the present
invention are applied not only to the fourth embodiment shown in
FIGS. 21, 22A, and 22B, but also to the first embodiment to the
third embodiment and other embodiments following the fifth
embodiment.
[0160] Further, the following is advantageous in structure. Since
the combustion chamber is divided into the annular container 312
and a downstream structure (secondary annular container), the
annular container 312 can readily be taken out. As compared to the
conventional technology, disassembly, replacement, and adjustment
of the combustion apparatus are facilitated to improve easiness of
maintenance.
[0161] Next, a combustion apparatus according to a fifth
embodiment, which is compatible with the fourth embodiment, will be
described with reference to FIG. 23. FIG. 23 shows an embodiment of
a combustion apparatus having an annular container 512 in which the
close end 510 of the annular container is formed by a curved
surface in which a cross-sectional curve Lr is formed by a
free-form arc having a nonuniform curvature, unlike the first
embodiment to the fourth embodiment.
[0162] In the example shown in FIG. 23, most parts of the annular
container 512 are formed by the close end 510 having a curved
surface. A secondary annular container 402 is connected to an
extremely short inner cylindrical portion 515 of the annular
container 512 via a second connecting member 470 and to an outer
cylindrical portion 513 via a connecting member 270.
[0163] The combustion apparatus in the fifth embodiment can also
achieve the same effects as described in the fourth embodiment.
Since the close end 510 of the annular container 512 is formed by a
curved surface, it is possible to facilitate manufacturing and
reduce cost in a case where the annular container 512 is made of a
heat resistant material such as ceramics, particularly, for the
purpose of a high combustion temperature. Further, since the
combustion chamber is divided into the annular container 512 and a
downstream structure (secondary annular container 402), the annular
container 512 can readily be taken out. As compared to the
conventional technology, disassembly, replacement, and adjustment
of the combustion apparatus are facilitated to improve easiness of
maintenance. The annular container 512 partially including a curved
surface in the fifth embodiment may be applied to the first
embodiment to the third embodiment.
[0164] Next, a combustion apparatus according to a sixth embodiment
will be described with reference to FIG. 24. The combustion
apparatus shown in FIG. 24 is an application of the fourth
embodiment shown in FIGS. 11 and 12. That is, auxiliary air holes
are formed in the outer cylindrical portion of the annular
container in the fourth embodiment. Specifically, in the embodiment
of FIG. 24, the combustion apparatus in the sixth embodiment has a
plurality of auxiliary air holes 619 formed in an outer cylindrical
portion 613 near the close end 610 of the annular container
612.
[0165] The combustion air 22d flowing through a plurality of
auxiliary air holes 619 thus formed in the outer cylindrical
portion 613 near the close end 610 flows centrally into the annular
container 612 in a jet state. Accordingly, the combustion gas 24b
therearound is induced so as to promote a flow directed from the
outer area (outer cylindrical portion) 613 of the annular container
612 to the inner area (inner cylindrical portion) 615 near the
close end 610 of the container 612. The swirling and flowing
combustion gas 28 can be introduced into a portion near the inner
area (inner cylindrical portion) 615 of the annular container 612
at a location near the close end 610 of the annular container 612
and recirculated toward the fuel track 23. The auxiliary air holes
619 in the sixth embodiment may be applied to the first embodiment,
the second embodiment, and the third embodiment.
[0166] Next, a combustion apparatus according to a seventh
embodiment will be described with reference to FIG. 25. FIG. 25
shows an embodiment of the combustion apparatus in which a
plurality of guide vanes 11 are provided as a flow adjusting
structure inside of the close end 210 of the annular container 312
in the fourth embodiment (see FIGS. 11 and 12). Such guide vanes 11
can achieve the same effects as the auxiliary air holes 619 in the
sixth embodiment (see FIG. 24). This embodiment is substantially
the same as the fourth embodiment except that a plurality of guide
vanes 11 are provided as a flow adjusting structure inside of the
close end 210 of the annular container 312. Further, the guide
vanes 11 can also be applied to the first embodiment to the third
embodiment and the sixth embodiment.
[0167] Next, a combustion apparatus according to an eighth
embodiment will be described with reference to FIG. 26. FIG. 26
shows an embodiment of the combustion apparatus in which a
plurality of guide vanes 11a are provided as a flow adjusting
structure on an inner surface of the outer cylindrical portion 213
of the annular container 312 of the fourth embodiment and near the
close end 210 to achieve the same effects as the auxiliary air
holes 619 in the sixth embodiment (see FIG. 24). This embodiment is
substantially the same as the fourth embodiment except that a
plurality of guide vanes 11a are provided as a flow adjusting
structure on the inner surface of the outer cylindrical portion 213
of the annular container 312 and near the close end 210. Further,
the guide vanes 11a can also be applied to the first embodiment to
the third embodiment and the sixth embodiment. Furthermore, the
flow adjusting structure shown in the seventh embodiment and the
eighth embodiment may be both provided.
[0168] Next, a combustion apparatus according to a ninth embodiment
will be described with reference to FIG. 27. In the combustion
apparatus shown in FIG. 27, the similar guide vanes to the seventh
embodiment and the eighth embodiment are applied to the fifth
embodiment shown in FIG. 23. Specifically, in the illustrated
embodiment, guide vanes 11b are formed so as to extend along an
inner curved surface of the close end 510 of the annular container
512, which is formed by a curved surface, substantially to a top of
the close end 510.
[0169] Each of the guide vanes 11, 11a, and 11b shown in the
seventh embodiment to the ninth embodiment has a function to
suppress a swirling flow and regulate the flow in a radial
direction near the close end 210 or 510 of the annular container
212 or 512. As a result, the swirling and flowing combustion gas
24a (not shown) can be introduced into an inner portion of the
close end 210 or 510 of the annular container 212 or 512 and
smoothly recirculated toward the fuel track 23, as with the fifth
embodiment.
[0170] A tenth embodiment to a twelfth embodiment, which are
further developments of the seventh embodiment to the ninth
embodiment, will be described with reference to FIGS. 28 through
30.
[0171] First, in the tenth embodiment shown in FIG. 28, the guide
vanes 11 as a flow adjusting structure in the seventh embodiment
shown in FIG. 25 are optimized. Specifically, guide vanes 11c in
the tenth embodiment are curved in an arc form such that the shape
of the guide vanes 11 in the seventh embodiment shown in FIG. 25
spirals toward the inner cylinder 215 of the annular container 312
so as to facilitate the flow of the combustion air flowing into the
central portion of the annular container 312. The guide vanes 11c
can also be applied to the first embodiment to the third embodiment
and the sixth embodiment. Further, the guide vanes 11c can be used
together with the guide vanes 11a in the eighth embodiment.
[0172] In the eleventh embodiment shown in FIG. 29, the guide vanes
11a as a flow adjusting structure in the eighth embodiment shown in
FIG. 26 are optimized. Specifically, guide vanes 11d in the
eleventh embodiment are deformed such that the shape of the guide
vanes 11a in the eighth embodiment shown in FIG. 26 is inclined
along an inner wall of the outer cylindrical portion 312 of the
annular container 212 while upper ends of the guide vanes 11d are
directed in a vertical direction in the illustrated example. The
guide vanes 11d can also be applied to the first embodiment to the
third embodiment and the sixth embodiment. Further, the guide vanes
11d can be used together with the guide vanes 11 in the seventh
embodiment or the guide vanes 11c shown in the tenth
embodiment.
[0173] In the twelfth embodiment shown in FIG. 30, the guide vanes
11b as a flow adjusting structure in the ninth embodiment shown in
FIG. 27 are optimized. Specifically, guide vanes 11e in the twelfth
embodiment are deformed such that the shape of the guide vanes 11b
in the ninth embodiment shown in FIG. 27 is inclined along a curved
inner wall of the outer cylindrical portion 513 of the annular
container 512 while upper ends of the guide vanes 11e are directed
in a vertical direction in the illustrated example.
[0174] In the tenth embodiment to the twelfth embodiment, the flow
adjusting structure (guide vanes) 11c, 11d, or 11e has an effect to
centrally deflect a flow of the swirling combustion gas 24a (not
shown) positively and more smoothly. Thus, the swirling and flowing
combustion gas 24a can be more smoothly introduced into the inner
area (inner cylindrical portion) 215 or 515 of the annular
container 212 or 512 and recirculated toward the fuel track 23 near
the close end 210 or 510 of the annular container 212 or 512.
[0175] Even if the detail of the shape of the flow adjusting
structure is changed, it is substantially equivalent to the above
flow adjusting structure as long as it has an effect to deflect the
swirling flow into a centrally directed flow. Further, the flow
adjusting structure may include plate-like or stand-like objects
attached to the annular container 212 or 512, or may include
grooves formed in the inner surface of the annular container 212 or
512.
[0176] Next, a combustion apparatus according to a thirteenth
embodiment, which is an application of the fourth embodiment, will
be described with reference to FIG. 31. In this combustion
apparatus, auxiliary fuel nozzles 702 for accessorily injecting
fuel are provided on an inner surface of the outer cylindrical
portion 713 of the annular container 712 which has the inner
cylindrical portion 715 and the outer cylindrical portion 713.
These fuel nozzles 702 are positioned slightly away from the inflow
portions 20 for the combustion air 22 toward the close end 710.
[0177] Fuel injected from the auxiliary fuel nozzles 702 may be the
same as or different from the fuel injected from the main fuel
nozzle 18. Even if the fuel 21 has a difficulty to reach the inflow
portions 20 (not shown) for the combustion air 22 because the
combustion apparatus has a large size or a limited injection
pressure in a case of gaseous fuel, injection of the same fuel from
the auxiliary fuel nozzles 702 achieves combustion with suppressing
generation of thermal NOx due to burnt gas recirculation, as with
the second embodiment.
[0178] Further, liquid/gas multi fuel combustion can be achieved
with a simple arrangement by injecting liquid fuel from the fuel
nozzle 18 and injecting gaseous fuel from the auxiliary fuel
nozzles 702. Turndown performance can further be improved by the
auxiliary fuel nozzles 702. Further, when fuel having such a low
heating value that stable combustion is difficult is used,
particularly when fuel like waste liquid, which has a low heating
value, is used, injection of fuel having a low heating value or
waste liquid from the fuel nozzle 18 and injection of fuel having
good combustibility from the auxiliary fuel nozzles 702 produce
pre-evaporated and premixed fuel by burnt gas recirculation to
achieve combustion with suppressing generation of thermal NOx, as
with the fourth embodiment.
[0179] In FIG. 31, the auxiliary fuel nozzles 702 include a
plurality of nozzles provided on the inner surface of the outer
cylindrical portion 713 of the annular container 712. As another
arrangement, a single ring having a large number of injection holes
(not shown) may be disposed on the inner surface of the outer
cylindrical portion 713 of the annular container 712.
[0180] The auxiliary fuel nozzles 702 in the thirteenth embodiment
are also applicable to the first embodiment to the third embodiment
and the fifth embodiment to the twelfth embodiment.
[0181] When the present invention is applied to a combustion
apparatus in a gas turbine, the aforementioned embodiments (the
first embodiment to the thirteenth embodiment) are regarded as a
primary combustion zone, and additional air inflow portions are
provided downstream of the outlet 26. Meanwhile, in a combustion
apparatus of a gas turbine, many technologies have been known to
add air downstream of a primary combustion zone in order to prevent
a lowered combustion efficiency which causes discharge of unburnt
components or an increased generation of NOx. Accordingly, when the
present invention is applied to a gas turbine, known technology can
be applied to the aforementioned embodiments. Thus, many
applications can be obtained within the concept of the present
invention. Not all of such applications can be explained and some
examples of such applications will be described below.
[0182] A combustion apparatus in a gas turbine according to a
fourteenth embodiment will be described with reference to FIGS. 32
and 33. In the fourteenth embodiment shown in FIGS. 32 and 33, the
combustion apparatus in the aforementioned fourth embodiment is
applied to a gas turbine combustion apparatus.
[0183] As compared to the fourth embodiment, in the gas turbine
combustion apparatus shown in FIGS. 32 and 33, the secondary
annular container is replaced with a secondary annular container
802 which is extended toward the outlet and has air holes 814 and
814b formed at proper positions. Further, the secondary annular
container 802 is enlarged (808) in cross-section at a downstream
portion which is arbitrary. Furthermore, although the secondary
annular container 802 is integrally formed including the outlet 26,
it may be divided for manufacturing requirements.
[0184] Secondary and dilution air 818 flows through the air holes
814 and 814b formed as a plurality of stages in the secondary
annular container 802. As with the fourth embodiment, burnt gas
recirculation occurs uniformly along a fuel track 23 in the primary
combustion zone 816 to perform combustion with a combustion gas
having a high temperature and a low oxygen concentration.
Accordingly, pre-evaporation combustion is achieved in a case of
liquid fuel, and premixed combustion and slow combustion are
achieved in a case of gaseous fuel or liquid fuel. Uniform
combustion with a low maximum flame temperature can be performed
(unlike usual diffusive combustion in which areas having a
theoretical mixture ratio and a high temperature are produced
locally in the combustion). An average flame temperature is lowered
due to the heat capacity of an inert gas in the combustion gas.
Accordingly, generation of thermal NOx is suppressed. The inner
wall surface of the outer cylinder 806 to the uppermost secondary
air holes 814 of the secondary annular container 802 is cooled by a
portion of the primary air 817 as with the fourth embodiment.
[0185] Cooling air holes 814b may optionally be formed in a wall
surface of the outer cylinder 806 of the secondary annular
container 802. A gas having a high temperature passes near an inner
side portion 215 of the annular container 312 and a surface of the
inner cylinder 804 in the secondary annular container 802.
Accordingly, air holes may be provided in the inner side portion
215 of the annular container 312 and the inner cylinder 804 of the
secondary annular container 802 so as to inject cooling air in a
jet state or along the wall surface as needed. When the inner side
portion 215 of the annular container 312 and the inner cylinder 804
of the secondary annular container 802 are made of a heat resistant
material, no air inflow holes may be formed in the inner side
portion 312 of the annular container 212 and the inner cylinder 804
of the secondary annular container 802.
[0186] Further, because the stability of the primary combustion
zone 816 is high, a ratio of a flow rate of the primary air 817 to
a total flow rate of air can be increased to perform leaner primary
combustion so as to lower a combustion temperature. Accordingly, t
is possible to further suppress generation of thermal NOx. Further,
since the combustion chamber is divided into the annular container
312 and a downstream structure (secondary annular container 802),
the annular container 312 can readily be taken out. As compared to
the conventional technology, disassembly, replacement, and
adjustment of the combustion apparatus are facilitated to improve
easiness of maintenance.
[0187] When the first embodiment to the third embodiment and the
sixth embodiment to the thirteenth embodiment are applied to a gas
turbine combustion apparatus instead of the fourth embodiment, it
is possible to achieve the operations and effects of the fourteenth
embodiment. At that time, the operations and effects of the first
embodiment to the third embodiment and the sixth embodiment to the
thirteenth embodiment can also be achieved.
[0188] Next, a gas turbine combustion apparatus to a fifteenth
embodiment will be described with reference to FIG. 34. In the
fifteenth embodiment shown in FIG. 34, the combustion apparatus in
the fifth embodiment is applied to a gas turbine combustion
apparatus. As compared to the fifth embodiment, in the gas turbine
combustion apparatus shown in FIG. 34, the secondary annular
container is replaced with a secondary annular container 802 which
is extended toward the outlet 26 and has air holes 814 and 814b
formed at proper positions. Further, the secondary annular
container 802 is enlarged in cross-section at a downstream portion,
which is arbitrary. Furthermore, although the secondary annular
container 802 is integrally formed including the outlet 26, it may
be divided for manufacturing requirements. Secondary and dilution
air 818 flows through the air holes 814 and 814b formed as a
plurality of stages in the secondary annular container 802.
[0189] As with the fifth embodiment, burnt gas recirculation occurs
uniformly along a fuel track 23 in the primary combustion zone 816
to perform combustion with a combustion gas having a high
temperature and a low oxygen concentration. Accordingly,
pre-evaporation combustion is achieved in a case of liquid fuel,
and premixed combustion and slow combustion are achieved in a case
of gaseous fuel or liquid fuel. Uniform combustion with a low
maximum flame temperature can be performed (unlike usual combustion
in which areas having a theoretical mixture ratio and a high
temperature are produced locally in the combustion). An average
flame temperature is lowered due to the heat capacity of an inert
gas in the combustion gas. Accordingly, generation of thermal NOx
is suppressed. The inner wall surface of the outer cylinder 806 to
the uppermost secondary air holes 814 of the secondary annular
container 802 is cooled by a portion of the primary air 817 as with
the fifth embodiment.
[0190] Cooling air holes 814b may optionally be formed in a wall
surface of the outer cylinder 806 of the secondary annular
container 802 as shown in FIG. 34. A gas having a high temperature
passes near an inner side of the annular container 512 and an inner
surface of the inner cylinder 804 in the secondary annular
container 802. Accordingly, air holes 814 may be provided in the
inner circumferential surface of the annular container 512 and the
inner cylinder 804 of the secondary annular container 802 so as to
inject cooling air in a jet state or along the wall surface as
needed. When the annular container 512 and the inner cylinder 804
of the secondary annular container 802 are made of a heat resistant
material, no air inflow holes may be formed in the annular
container 512 and the inner cylinder 804 of the secondary annular
container 802.
[0191] Further, because the stability of the primary combustion
zone 816 is high, a ratio of a flow rate of the primary air 817 to
a total flow rate of air can be increased to perform leaner primary
combustion so as to lower a combustion temperature. Accordingly, it
is possible to further suppress generation of thermal NOx. Since
the close end 510 of the annular container 512 is formed by a
domelike curved surface, it is possible to facilitate manufacturing
and reduce cost in a case where the annular container 512 is made
of a heat resistant material such as ceramics, particularly, for
the purpose of a high combustion temperature. Further, since the
combustion chamber is divided into the annular container 512 and a
downstream structure (secondary annular container 802), the annular
container 512 can readily be taken out. As compared to the
conventional technology, disassembly, replacement, and adjustment
of the combustion apparatus are facilitated to improve easiness of
maintenance.
[0192] Next, a gas turbine combustion apparatus to a sixteenth
embodiment will be described with reference to FIG. 35. The
sixteenth embodiment shown in FIG. 35 is an application of the
aforementioned fourteenth embodiment. Specifically, a secondary
swirler 815 is used instead of the air holes at a mixing portion of
secondary air 818 in the combustion apparatus of the fourteenth
embodiment shown in FIG. 31. Air holes 814 are formed in the inner
cylinder 804 of the secondary annular container 802, and air holes
814b are formed in the outer cylinder 806.
[0193] By forming a swirling flow of the secondary air 818 with the
secondary swirler 815, it is possible to promote mixing in a
secondary zone. When air is to be added downstream of a primary
combustion zone, known technology can be employed in order to
prevent a lowered combustion efficiency which causes discharge of
unburnt components or an increased generation of NOx. Thus, various
applications can be obtained within the concept of the present
invention.
[0194] In the aforementioned embodiments, air is supplied into the
combustion chamber while being swirled. FIGS. 36 and 37 show an
example in which air is supplied without being swirled. Instead of
the swirler, the combustion apparatus shown in FIGS. 36 and 37 uses
introduction passages 17 for supplying air so as to have only a
velocity component in a direction facing a flow of fuel with
respect to a direction of a central axis of the combustion chamber
at air inflow portions 20. With this arrangement, the following
flow state can be formed. A track of an air flow and a track of a
fuel flow are not the same. The track of the air flow and the track
of the fuel flow intersect each other two times. The first
intersection of the air flow with the track of the fuel flow is
located near a tip of the fuel track, and the second intersection
of the air flow with the track of the fuel flow is located in a
region from a root of the track of the fuel flow to the vicinity of
the tip.
[0195] FIGS. 36 and 37 show an arrangement in which no swirler is
used in the second embodiment. No swirler may be used in the first
and third to sixteenth embodiments. However, in the first to
sixteenth embodiments using a swirler, the air flow becomes a
swirling flow swirling along an inner wall surface of the
combustion apparatus, so that centrifugal forces are applied to the
air flow. Accordingly, the air flow can go upstream smoothly along
the inner surface of the outer circumferential surface of the
combustion apparatus by a long distance before the air flow changes
its direction to a direction of the outlet of the combustion
apparatus. Specifically, the arrangement shown in the first to
sixteenth embodiments can form the aforementioned flow state more
efficiently as compared to the arrangement representatively shown
in FIGS. 36 and 37.
[0196] Next, an example in which a combustion apparatus of the
aforementioned embodiments is applied to a gas turbine generator
will be described with reference to FIG. 38. The gas turbine
generator shown in FIG. 38 has a gas turbine apparatus 900 and a
power generator 902.
[0197] The gas turbine apparatus 900 has a turbine 904 rotated by a
combustion gas, a combustor 906 for combusting a gaseous mixture of
fuel and air, a fuel control valve 908 for adjusting the amount of
fuel to be supplied to the combustor 906, an air compressor 910 for
transferring air to the combustor 906 under pressure, and a
controller 912 for indirectly controlling the turbine 904. The
combustion apparatus of the aforementioned embodiments is used as
the combustor 906 in FIG. 38.
[0198] The turbine 904 has a plurality of rotary vanes, which are
not shown in the drawings, rotated by receiving a combustion gas
926, is connected to the air compressor 910 via a rotational shaft
914, and is rotatably supported in a casing, which is not shown in
the drawings. The air compressor 910 is driven via the rotational
shaft 914 by the turbine 904 and is configured so as to compress
air 916 supplied into the air compressor 910. The air compressor
910 is connected to the combustor 906 via a pipe 918. The air 920
compressed by the air compressor 910 is supplied via the pipe 918
to the combustor 906.
[0199] The fuel control valve 908 is disposed upstream of the
combustor 906. Fuel 922 supplied from a fuel supply source, which
is not shown in the drawings, passes through the fuel control valve
908, and is then supplied to the combustor 906. The fuel control
valve 908 is operable to vary an opening of the valve. The opening
is controlled via a control signal line 924 by the controller 912
to adjust the amount of fuel 922 to be supplied to the combustor
906.
[0200] The fuel 922 and the compressed air 920 supplied to the
combustor 906 form a gaseous mixture in the combustor 906. When the
gaseous mixture is combusted in the combustor 906, a combustion gas
926 having a high temperature and a high pressure is generated. The
generated combustion gas 926 having a high temperature and a high
pressure is supplied to the turbine 904 to rotate the turbine 904
at a high speed. The turbine 904 is coupled directly to the power
generator 902 via the rotational shaft 914. When the turbine 904 is
rotated, the power generator 902 is rotated to generate power.
[0201] A rotational speed detector 928 for detecting a rotational
speed of the turbine 904 is provided near the rotational shaft 914
(near the power generator 902 in FIG. 38). Information of the
rotational speed detected by the rotational speed detector 928 is
transmitted through a signal line 930 to the controller 912. An
arrangement and effects of the combustor 906 are the same as those
of the combustion apparatus in the aforementioned embodiments.
[0202] As described above, when the embodiments of the present
invention are applied to a general combustion apparatus, it is
possible to positively control and generate burnt gas recirculation
with a simple structure. Thus, the stability can be enhanced and
effects of burnt gas recirculation can be maximized.
[0203] Further, since effects of burnt gas recirculation can be
maximized with high stability, it is possible to perform combustion
with a combustion gas having a high temperature and a low oxygen
concentration to achieve pre-evaporation combustion having stable
evaporation characteristics in a case of liquid fuel, premixed
combustion independent of gaseous fuel or liquid fuel, slow
combustion, uniform combustion with a low maximum flame
temperature, and combustion with a low average flame temperature
due to the heat capacity of an inert gas in the combustion gas.
Thus, it is possible to provide a combustion apparatus which can
suppress generation of thermal NOx, which has been difficult to
suppress with the conventional technology.
[0204] Since an inner wall of the combustion apparatus is suitably
cooled by an air flow having a low temperature, it is possible to
provide a combustion apparatus having a high durability.
[0205] Alternatively, it is possible to provide a combustion
apparatus which can readily use a heat resistant material such as
ceramics. Further, since disassembly and replacement are
facilitated, it is possible to provide a combustion apparatus
having easiness of maintenance.
[0206] When auxiliary fuel nozzles are provided, it is possible to
provide a combustion apparatus which can suppress generation of
thermal NOx in multi fuel combustion of gaseous fuel/liquid fuel
and combustion with fuel or a waste liquid having a low heating
value.
[0207] When the aforementioned embodiments are applied to a primary
combustion zone of a gas turbine combustion apparatus, it is
possible to positively control and generate burnt gas recirculation
with a simple structure. Thus, the stability can be enhanced in a
primary combustion zone, and effects of burnt gas recirculation can
be maximized.
[0208] Further, since effects of burnt gas recirculation can be
maximized with high stability, it is possible to perform combustion
with a combustion gas having a high temperature and a low oxygen
concentration to achieve pre-evaporation combustion having stable
evaporation characteristics in a case of liquid fuel, in which it
has been difficult to reduce NOx with the conventional technology,
premixed combustion independent of gaseous fuel or liquid fuel,
slow combustion, uniform combustion with a low maximum flame
temperature, and combustion with a low average flame temperature
due to the heat capacity of an inert gas in the combustion gas.
Further, since a primary combustion zone can be designed so as to
be leaner, it is possible to provide a gas turbine combustion
apparatus which can suppress generation of thermal NOx by lowering
a combustion temperature.
[0209] Furthermore since an inner wall of the combustion apparatus
is suitably cooled by an air flow having a low temperature, it is
possible to provide a gas turbine combustion apparatus having a
high durability.
[0210] Further, it is possible to provide a gas turbine combustion
apparatus which can readily use a heat resistant material such as
ceramics. Furthermore, since disassembly and replacement are
facilitated, it is possible to provide a gas turbine combustion
apparatus having easiness of maintenance.
[0211] When auxiliary fuel nozzles are provided, it is possible to
provide a gas turbine combustion apparatus which can suppress
generation of thermal NOx in multi fuel combustion of gaseous
fuel/liquid fuel and combustion with fuel or a waste liquid having
a low heating value.
[0212] The embodiments described above can be modified within the
scope of the present invention. A technical extension of the
present invention should be determined based on the description of
claims. That is, the illustrated embodiments are described by way
of example, and do not limit the scope of the present
invention.
[0213] For example, in the first embodiment to the fourth
embodiment, each of the containers 12, 112, 212, and 312 has an
annular (ring) cross-sectional shape. However, the cross-sectional
shape of the container may be changed into a desired shape.
Further, the container may have an annular shape including two
polygons in which one completely encloses the other as long as a
swirling flow is formed in the container. Alternatively, the
cross-sectional shape of the container 12, 112, 212, or 312 may be
varied in an axial direction at a location (axial location) other
than locations at which the air inflow portions 20 are formed.
[0214] Further, air inflow ports may arbitrarily be provided on the
annular container 12, 112, 212, or 312 or the inner side portion of
the secondary annular container 402, mainly for cooling wall
surfaces of the annular container 12, 112, 212, or 312 or the
secondary annular container 402. When the inner side of the annular
container 12, 112, 212, or 312, or the inner cylinder 404 of the
secondary annular container 402 is made of a heat resistant
material, such air inflow holes may not be provided. Further,
combustion air required for combustion may be supplied through
these air holes at the downstream side of the air inflow portions
20. The aforementioned equivalent structures of the container can
be applied to all of the aforementioned embodiments.
[0215] Further, the shape of the inflow casing 14 may arbitrarily
be deflected in the first embodiment to the fourth embodiment. For
example, the inflow casing of the embodiments, which has a
structure in which air flows from the close end 10, 110, or 210 in
the axial direction, may be replaced with a structure having a
scroll shape through which air flows in a circumferential direction
and a shape to allow air to flow from a periphery of the outlet of
the annular container 12, 112, 212, or 312 or the secondary annular
container 402 in an opposite direction, which is not shown in the
drawings. Further, as shown in FIG. 16, a back flow type inflow
casing 14a, which is suitable for a centrifugal compressor and a
turbine, may be used.
[0216] The embodiments described above can be varied within the
scope of the present invention. A technical extension of the
present invention should be determined based on the description of
claims. That is, the illustrated embodiments are described by way
of example, and do not limit the scope of the present
invention.
INDUSTRIAL APPLICABILITY
[0217] The present invention is suitably used for a combustion
apparatus for supplying combustion air and fuel to a combustion
chamber to mix and combust the combustion air and the fuel.
* * * * *