U.S. patent application number 14/127569 was filed with the patent office on 2014-05-08 for burner for exhaust purifying device.
This patent application is currently assigned to HINO MOTORS, LTD.. The applicant listed for this patent is HINO MOTORS, LTD.. Invention is credited to Ryo Shibuya, Ichiro Tsumagari.
Application Number | 20140123632 14/127569 |
Document ID | / |
Family ID | 49623869 |
Filed Date | 2014-05-08 |
United States Patent
Application |
20140123632 |
Kind Code |
A1 |
Shibuya; Ryo ; et
al. |
May 8, 2014 |
BURNER FOR EXHAUST PURIFYING DEVICE
Abstract
A burner used in an exhaust purifying device that purifies
exhaust in an exhaust pipe of a diesel engine is provided with a
tubular flame stabilizer including an ejection port from which
fluid generated through combustion is ejected. The flame stabilizer
includes a connecting passage, which connects the interior of the
flame stabilizer and the exterior of the flame stabilizer. A
recirculation unit is arranged at an outer side of the flame
stabilizer. The recirculation unit includes a flow receiving
portion that receives the fluid ejected from the ejection port, and
an outer guiding portion that guides the fluid received by the flow
receiving portion to the connecting passage.
Inventors: |
Shibuya; Ryo; (Hino-shi,
JP) ; Tsumagari; Ichiro; (Hino-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HINO MOTORS, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
HINO MOTORS, LTD.
Tokyo
JP
|
Family ID: |
49623869 |
Appl. No.: |
14/127569 |
Filed: |
May 22, 2013 |
PCT Filed: |
May 22, 2013 |
PCT NO: |
PCT/JP2013/064240 |
371 Date: |
December 19, 2013 |
Current U.S.
Class: |
60/303 |
Current CPC
Class: |
F23G 7/065 20130101;
F01N 2240/14 20130101; F23C 2900/06041 20130101; Y02T 10/26
20130101; Y02T 10/12 20130101; F23D 11/24 20130101; F23C 9/006
20130101; F23D 11/402 20130101; F23C 2201/20 20130101; F01N 3/0253
20130101; F23C 7/002 20130101; F23D 11/406 20130101; F01N 3/2033
20130101 |
Class at
Publication: |
60/303 |
International
Class: |
F01N 3/025 20060101
F01N003/025 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2012 |
JP |
2012-119897 |
Claims
1. A burner used in an exhaust purifying device that purifies
exhaust in an exhaust pipe of an engine, the burner comprising: a
tubular flame stabilizer including an ejection port in a distal end
to eject fluid generated through combustion; a connecting passage
that connects an interior of the flame stabilizer and an exterior
of the flame stabilizer; and a recirculation unit arranged at an
outer side of the flame stabilizer, wherein the recirculation unit
includes, a flow receiving portion that receives the fluid ejected
from the ejection port, and a guiding portion that guides the fluid
received by the flow receiving portion from the flow receiving
portion to the connecting passage.
2. The burner according to claim 1, wherein the flow receiving
portion is formed to be annular to face an edge of the ejection
port in an axial direction of the flame stabilizer.
3. The burner according to claim 2, wherein the guiding portion is
formed to surround the flame stabilizer.
4. The burner according to claim 2, wherein the guiding portion
includes a tubular outer guiding portion that surrounds the flame
stabilizer, and a tubular inner guiding portion that extends from
an inner edge of the flow receiving portion toward the ejection
port.
5. The burner according to claim 1, wherein the connecting passage
is arranged closer to a basal end of the flame stabilizer with
respect to a middle of the flame stabilizer in the axial
direction.
6. The burner according to claim 1, wherein the flame stabilizer
includes an inner tube and an outer tube that surrounds the inner
tube, the flame stabilizer is connected to an air supply pipe that
supplies air to a gap between the inner tube and the outer tube,
and the inner tube includes an air supplying hole that connects the
gap between the inner tube and the outer tube with the interior of
the inner tube.
7. The burner according to claim 1, wherein the distal end of the
flame stabilizer has an enlarged diameter.
8. The burner according to claim 1, further comprising an ignition
unit in the flame stabilizer.
9. The burner according to claim 1, wherein the interior of the
flame stabilizer is partitioned into a premixing chamber, which
generates a mixture of fuel and air, and a combustion region, which
burns the mixture supplied from the premixing chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national stage application under 35
U.S.C. 371 and claims the benefit of PCT Application No.
PCT/JP2013/064240 filed 22 May 2013, which designated the United
States, which PCT Application claimed the benefit of Japanese
Patent Application No. 2012-119897 filed 25 May 2011, the
disclosure of each of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The technique of the present disclosure relates to a burner
used in an exhaust purifying device that purifies exhaust from an
engine with a filter or a catalyst.
BACKGROUND OF THE INVENTION
[0003] Patent document 1 describes an example of a widely used
engine exhaust purifying device that captures particulates in the
exhaust with a diesel particulate filter (hereinafter referred to
as filter). In the exhaust purifying device, the particulates in
the exhaust are captured with the filter to purify the exhaust.
However, the particulates need to be removed from the filter to
maintain the function of the filter.
[0004] A known exhaust purifying device capable of removing the
particulates from the filter is a device including a burner that
heats the exhaust delivered to the filter by burning the fuel for
driving the engine. In the exhaust purifying device that includes
the burner, when the amount of particulates deposited on the filter
exceeds a predetermined amount, the burner burns the fuel to heat
the exhaust and raise the temperature of the filter until soot,
which is the main component of the particulates, is oxidized. This
removes the particulates deposited on the filter and allows for the
regenerated filter to capture the particulates in the exhaust
again.
PRIOR ART DOCUMENT
Patent Document
[0005] Patent Document 1: Japanese Laid-Open Patent Publication No.
2011-157824
SUMMARY OF THE INVENTION
[0006] The temperature of the engine and the temperature of the
exhaust are low immediately after the engine is started compared to
when the engine has been continuously operating. This lowers the
temperature in the burner that burns fuel. As a result, the mixture
of fuel and air becomes difficult to ignite compared to when the
temperature in the burner is high. This increases fuel consumption
when the temperature of the filter is raised to the same
extent.
[0007] Such a problem occurs not only in a burner that regenerates
the filter as described above but also in other burners that use
some of the engine driving fuel for heating, for example, a burner
that raises the temperature of the catalyst arranged in the exhaust
purifying device. Further, it is desirable that fuel consumption be
reduced not only when the engine is started as described above but
also when the engine is continuously operating.
[0008] It is an object of the technique of the present disclosure
to provide a burner for an exhaust purifying device capable of
improving the efficiency for burning fuel.
[0009] One aspect of the present disclosure is a burner used in an
exhaust purifying device that purifies exhaust in an exhaust pipe
of an engine. The burner is provided with a tubular flame
stabilizer, a connecting passage, and a recirculation unit. The
flame stabilizer includes an ejection port in a distal end to eject
fluid generated through combustion. The connecting passage connects
an interior of the flame stabilizer and an exterior of the flame
stabilizer. A recirculation unit is arranged at an outer side of
the flame stabilizer. The recirculation unit includes a flow
receiving portion that receives the fluid ejected from the ejection
port, and a guiding portion that guides the fluid received by the
flow receiving portion from the flow receiving portion to the
connecting passage.
[0010] In the aspect described above, some of the fluid generated
by the combustion of fuel in the flame stabilizer is received by
the flow receiving portion of the recirculation unit and then
guided by the guiding portion to the connecting passage formed in
the flame stabilizer. Therefore, the high temperature fluid
generated by the combustion flows into the region surrounded by the
flame stabilizer and raises the temperature in the flame
stabilizer. This increases the efficiency for burning fuel in the
flame stabilizer.
[0011] In another aspect of the burner according to the present
disclosure, the flow receiving portion is formed to be annular to
face an edge of the ejection port in an axial direction of the
flame stabilizer.
[0012] The fluid ejected from the ejection port includes the fluid
diffused to the periphery of the ejection port and the fluid
substantially flowing straight from the ejection port. The fluid
diffused to the periphery of the ejection port normally strikes
pipes and the like surrounding the ejection port thereby raising
the temperature of the pipes, and then reaches a heating subject in
the ejection direction. The fluid substantially flowing straight
from the ejection port along the axis of the flame stabilizer
reaches the heating subject without striking pipes and the like.
Thus, the fluid substantially flowing straight from the ejection
port is preferably used for the heating in terms of increasing the
temperature rising rate of the heating subject.
[0013] According to the flow receiving portion in the other aspect
described above, the flow receiving portion facing the edge of the
ejection port in the axial direction of the flame stabilizer guides
the fluid substantially flowing straight from the ejection port to
the target of heating. Thus, the temperature rising rate in the
target of heating can be increased compared to when the flow
receiving portion is arranged at a position facing the ejection
port, that is, a position facing the portion on the radially inner
side of the edge of the ejection port. The annular flow receiving
portion receives the fluid diffused from the ejection port and
guides the fluid to the guiding portion. Thus, the amount of fluid
guided to the interior of the flame stabilizer is increased
compared to when the corresponding flow receiving portion is
formed, for example, at only one part in the circumferential
direction of the ejection port. As a result, the temperature of the
interior of the flame stabilizer can be raised while suppressing
decreases in the temperature rising rate of the heating
subject.
[0014] In another aspect of the burner according to the present
disclosure, the guiding portion is formed to surround the flame
stabilizer.
[0015] According to the guiding portion of the other aspect
described above, the temperature of the flame stabilizer can be
raised at the periphery of the flame stabilizer and most of the
fluid flowing at the periphery of the flame stabilizer can be
guided to the interior of the flame stabilizer since the guiding
portion surrounds the flame stabilizer.
[0016] In another aspect of the burner according to the present
disclosure, the guiding portion includes a tubular outer guiding
portion that surrounds the flame stabilizer, and a tubular inner
guiding portion that extends from an inner edge of the flow
receiving portion toward the ejection port.
[0017] Most of the fluid received by the flow receiving portion
flows to either the direction toward the inner edge of the flow
receiving portion or the direction toward the outer edge of the
flow receiving portion. In this case, according to the guiding
portion of another aspect described above, most of the fluid
flowing toward the inner edge of the flow receiving portion flows
from the inner guiding portion toward the outer edge of the flow
receiving portion due to the striking with the inner guiding
portion. As a result, most of the fluid received by the flow
receiving portion is deviated toward the outer edge of the flow
receiving portion so that the fluid is easily guided into the flame
stabilizer as compared with the recirculation unit that includes
only the flow receiving portion.
[0018] In another aspect of the burner according to the present
disclosure, the connecting passage is arranged closer to a basal
end of the flame stabilizer with respect to a middle of the flame
stabilizer in the axial direction.
[0019] According to other aspect described above, the path of the
fluid that flows into the flame stabilizer is lengthened in the
interior of the flame stabilizer as compared to when the connecting
passage is formed closer to the distal end of the flame stabilizer.
Thus, the temperature of the interior of the flame stabilizer is
easily raised, and the fuel is easily burned in the flame
stabilizer.
[0020] In another aspect of the burner according to the present
disclosure, the flame stabilizer includes an inner tube and an
outer tube that surrounds the inner tube. The flame stabilizer is
connected to an air supply pipe that supplies air to a gap between
the inner tube and the outer tube. The inner tube includes an air
supplying hole that connects the gap between the inner tube and the
outer tube with the interior of the inner tube.
[0021] According to the other aspect described above, the air used
to burn fuel receives the heat of the fluid generated by the
combustion while being supplied to the interior of the inner tube
through the gap between the inner tube and the outer tube. Thus,
the air having a higher temperature is supplied to the interior of
the inner tube compared to when the air of the air supply pipe is
directly supplied to the interior of the inner tube. In particular,
when the guiding portion is formed to surround the flame
stabilizer, the flame stabilizer receives heat from the fluid
flowing through the gap between the outer tube of the flame
stabilizer and the guiding portion. Thus, the air passing through
the gap between the inner tube and the outer tube also receives
heat. This supplies the air having a higher temperature is supplied
to the interior of the inner tube. As a result, the temperature of
the interior of the inner tube is further raised, and the fuel is
more easily burned.
[0022] In another aspect of the burner according to the present
disclosure, the distal end of the flame stabilizer has an enlarged
diameter.
[0023] According to the other aspect described above, the fluid
from the ejection port is more easily received by the flow
receiving portion. Thus, the fluid guided to the interior of the
flame stabilizer by the recirculation unit further increases.
[0024] Another aspect of the burner according to the present
disclosure further includes an ignition unit in the flame
stabilizer.
[0025] The fuel or the components contained in the fuel may deposit
on the ignition unit of the burner when burning fuel. Such deposits
contain carbon that adversely affects the insulation of portions
where insulation is not necessary in the ignition unit. As a
result, the ignition of the air-fuel mixture in the ignition unit
becomes unstable. In this regard, according to the aspect described
above, the temperature of the ignition unit is raised when the
fluid of high temperature flows into the flame stabilizer. Thus,
the fuel and the components of the fuel are less likely to deposit
on the ignition unit. As a result, the ignition of the air-fuel
mixture in the ignition unit is less likely to be unstable, and the
fuel is easily burned.
[0026] In another aspect of the burner according to the present
disclosure, the interior of the flame stabilizer is partitioned
into a premixing chamber, which generates a mixture of fuel and
air, and a combustion region, which burns the mixture supplied from
the premixing chamber.
[0027] According to the other aspect described above, the fuel is
mixed with air in advance in the premixing chamber and supplied to
the combustion region, and the supplied mixture is burned in the
combustion region. Thus, the fuel is easily burned compared to when
the fuel and the air are supplied to the combustion region in a
non-mixed state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a block diagram showing the entire structure of a
diesel engine including a burner according to a first
embodiment.
[0029] FIG. 2 is a cross-sectional view of the burner in the first
embodiment.
[0030] FIG. 3 is a view showing the flow of fluid in the burner of
the first embodiment.
[0031] FIG. 4 is a cross-sectional view of a burner according to a
second embodiment.
[0032] FIG. 5 is a cross-sectional view taken along line 5-5 in
FIG. 4.
[0033] FIG. 6 is a cross-sectional view taken along line 6-6 in
FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0034] A first embodiment of a burner according to the present
disclosure will now be described with reference to FIG. 1 to FIG.
3. First, the entire structure of a diesel engine including the
burner will be described with reference to FIG. 1. The description
will focus on a passage for the air drawn into the diesel engine
and a passage of the exhaust discharged from the diesel engine, and
other parts will not be described. Hereinafter, "upstream" and
"downstream" are defined with respect to the direction in which air
and exhaust flows in the diesel engine.
[0035] [Schematic Structure of Diesel Engine]
[0036] As shown in FIG. 1, a cylinder block 11 of a diesel engine
10 includes six cylinders 11a arranging in a single row. An intake
manifold 12, which supplies intake air to each cylinder 11a, and an
exhaust manifold 16, into which the exhaust from each cylinder 11a
flows, are connected to the six cylinders 11a.
[0037] An intake pipe 13, which is a passage for the intake air, is
connected to the intake manifold 12. An air cleaner 14 is connected
to an upstream end of the intake pipe 13, and a compressor 15 of a
turbo charger TC is connected to the middle of the intake pipe 13.
An exhaust pipe 18 and an EGR pipe 17, which are passages for the
exhaust, are connected to the exhaust manifold 16. The EGR pipe 17
connects the intake pipe 13 and the exhaust manifold 16 to draw
exhaust into the intake pipe 13 by. A turbine 19, which is
connected to the compressor 15 described above, is connected to an
upstream portion of the exhaust pipe 18. An exhaust purifying
device 20 that purifies exhaust by removing particulates, for
example, soot, from the exhaust is arranged in a downstream portion
of the exhaust pipe 18.
[0038] The exhaust purifying device 20 includes a filter 21, which
captures the particulates suspended in the exhaust, and an exhaust
purification processing device burner (hereinafter referred to as
the burner 30), which heats the exhaust delivered to the filter 21
and which is located at the upstream side of the filter 21. The
filter 21 has a honeycomb structure made of, for example, porous
ceramic so that the particulates in the exhaust are captured in the
inner wall surfaces of a large number of pillars forming the
honeycomb structure.
[0039] An air supply pipe 13a connects the downstream portion of
the compressor 15 in the intake pipe 13 to the burner 30. An air
valve 13b is connected to the middle of the air supply pipe 13a.
Intake air is drawn from the intake pipe 13 into the exhaust
purifying device 20 through the air supply pipe 13a when the air
valve 13b is open, and the flow of intake air from the intake pipe
13 to the exhaust purifying device 20 is stopped when the air valve
13b is closed.
[0040] [Structure of Burner]
[0041] With reference to FIG. 2, the structure of the burner 30
will be described in further detail together with a part of the
structure of the exhaust purifying device 20.
[0042] The exhaust pipe 18, which extends in a radial direction of
a housing 20h, is connected to an end (basal end) closer to the
upstream side of the housing 20h, which is formed to be
cylindrical. The burner 30 and the filter 21 are arranged in the
housing 20h in order from upstream to downstream.
[0043] The burner 30 includes a flame stabilizer 31 formed to be
cylindrical and concentric with the housing 20h. The flame
stabilizer 31 is fixed to an upstream wall 20a, which is a wall of
the basal end in the housing 20h. A recirculation unit 32, which is
formed to be cylindrical and concentric with the flame stabilizer
31 is arranged on the outer side of the flame stabilizer 31, with a
gap formed with the flame stabilizer 31. The recirculation unit 32
is fixed to the upstream wall 20a. Two spark plugs 33a, 33b serving
as ignition units are fixed to the upstream wall 20a at the inner
side of the flame stabilizer 31. A fuel injection nozzle 34 is
fixed to the upstream wall 20a between the two spark plugs 33a, 33b
at the inner side of the flame stabilizer 31.
[0044] The flame stabilizer 31 has a dual tube structure including
an inner tube 41 and an outer tube 51 extending from the upstream
wall 20a toward the filter 21. Part of the basal end of the flame
stabilizer 31 is connected to the upstream wall 20a.
[0045] The inner tube 41 is formed to be cylindrical and concentric
with the housing 20h, and an ejection port 42 is formed at the
distal end of the inner tube 41. In other words, the distal end of
the inner tube 41 in the flame stabilizer 31 forms the ejection
port 42. The basal end of the inner tube 41 is spaced apart from
the upstream wall 20a by a passage formation portion 43, which is a
circumferential portion of the inner tube 41, and the basal end of
the inner tube 41 is connected to the upstream wall 20a by the
remaining circumferential portion of the inner tube 41.
[0046] The inner tube 41 includes a constant diameter portion 44,
which is a portion closer to the basal end, and an enlarged
diameter portion 45, which is a portion closer to the distal end. A
plurality of air supplying holes 46 extend through each of the
constant diameter portion 44 and the enlarged diameter portion 45.
The air supplying holes 46 are formed, for example, at a
predetermined interval in the circumferential direction of the
constant diameter portion 44 and at a predetermined interval in the
circumferential direction of the enlarged diameter portion 45.
[0047] The outer tube 51 is formed to be cylindrical and concentric
with the housing 20h, and surrounds the inner tube 41 with a gap
(air passage 52) formed between the outer tube 51 and the inner
tube 41. The distal end of the outer tube 51 is connected to the
distal end of the inner tube 41 over the entire circumferential
direction of the outer tube 51. This blocks the air passage 52,
which is the gap between the outer tube 51 and the inner tube 41.
The basal end of the outer tube 51 is connected to the passage
formation portion 43 of the inner tube 41 at a circumferential
portion of the outer tube 51 and fixed to the upstream wall 20a by
the remaining circumferential portion of the outer tube 51.
[0048] The air passage 52, which is the gap between the inner tube
41 and the outer tube 51, is connected with the air supply pipe 13a
through the upstream wall 20a by connecting the inner tube 41 and
the outer tube 51. Furthermore, a connecting passage 53 radially
extends through the inner tube 41 and the outer tube 51 to connect
the interior of the inner tube 41 and the exterior of the outer
tube 51 between the passage formation portion 43 and the upstream
wall 20a.
[0049] The recirculation unit 32 is formed to be cylindrical so as
to extend from the upstream wall 20a toward the filter 21 and
surround the entire flame stabilizer 31, and is bent back toward
the upstream wall 20a at a distal end positioned closer to the
filter 21 with respect to the flame stabilizer 31.
[0050] The recirculation unit 32 includes an outer guiding portion
61 serving as a guiding portion. The outer guiding portion 61 is
formed to be cylindrical and extends from the upstream wall 20a
toward the filter 21, and a gap connecting to the connecting
passage 53 is formed between the outer guiding portion 61 and the
flame stabilizer 31. The length in the axial direction of the outer
guiding portion 61 is set as an outer tube length L2, and the outer
tube length L2 is set to be longer than a flame stabilizer length
L1.
[0051] The recirculation unit 32 also includes an annular flow
receiving portion 62 facing the edge of the ejection port 42 in the
axial direction of the flame stabilizer 31. The flow receiving
portion 62 extends inward in the radial direction of the outer
guiding portion 61 over the entire circumferential direction of the
outer guiding portion 61 at the distal end of the outer guiding
portion 61.
[0052] The recirculation unit 32 further includes an inner guiding
portion 63 having a cylindrical shape extending from the inner edge
of the flow receiving portion 62 toward the ejection port 42. The
length in the axial direction of the inner guiding portion 63 is
set as an inner tube length L3, and the inner tube length L3 is set
to be shorter than the length obtained by subtracting the flame
stabilizer length L1 from the outer tube length L2.
[0053] The fuel injection nozzle 34 is, for example, connected to a
fuel pump for supplying fuel to the cylinder 11a. The fuel
injection nozzle 34 injects fuel into a region surrounded by the
flame stabilizer 31 at a predetermined frequency and a
predetermined pressure.
[0054] The spark plugs 33a, 33b include an anode rod 33a and a
cathode rod 33b. When voltage is applied between the anode rod 33a
and the cathode rod 33b, a spark discharge occurs between the anode
rod 33a and the cathode rod 33b. Flame F is generated in the flame
stabilizer 31 when the mixture of fuel and air is ignited and the
fuel in the flame stabilizer 31 is burned.
[0055] [Operation of Burner]
[0056] The regeneration of the filter 21 by the burner 30 will now
be described with reference to FIG. 3. In FIG. 3, the flow of
exhaust supplied from the exhaust pipe 18 to the exhaust purifying
device 20 is shown by thick arrows, the flow of air supplied from
the air supply pipe 13a is shown by broken line arrows, and the
flow of combustion gas generated by the combustion of fuel is shown
by solid line arrows. The combustion gas in this case includes gas
generated when burning the fuel. The combustion gas in this case
also includes gas in the flame stabilizer 31, which does not
contribute to the combustion of fuel but is heated by the flame F
generated in the flame stabilizer 31.
[0057] As shown in FIG. 3, in the burner 30, the air from the air
supply pipe 13a is first supplied to a combustion region, which is
a region surrounded by the inner tube 41, through the air passage
52 and the air supplying hole 46 of the flame stabilizer 31 when
performing regenerating the filter 21. The air supplied to the
combustion region is thus supplied in the direction from the
upstream wall 20a toward the filter 21. The exhaust supplied from
the exhaust pipe 18 into the exhaust purifying device 20 in this
case flows through the gap between the recirculation unit 32 and
the housing 20h in the direction from the upstream wall 20a toward
the filter 21. The exhaust raises the temperature of the entire
recirculation unit 32.
[0058] After the injection of fuel from the fuel injection nozzle
34 is started, voltage is applied to the spark plugs 33a, 33b. This
ignites the mixture of fuel and air. The flame F is generated in
the inner tube 41, and the fluid generated by combustion is ejected
from the ejection port 42 as combustion gas.
[0059] In this case, the temperature of the exhaust that comes into
contact with the recirculation unit 32 is raised since the
recirculation unit 32 is heated by the flame F generated in the
region surrounded by the flame stabilizer 31 and the recirculation
unit 32. When the flame F is generated beyond the distal end of the
recirculation unit 32, the exhaust passing between the distal end
of the recirculation unit 32 and the filter 21 is heated by the
flame F. The exhaust heated in such a manner is delivered to the
filter 21. This raises the temperature of the filter 21 to an
extent the soot deposited on the filter 21 is oxidized. The
temperature of the filter 21 can also be raised by supplying the
combustion gas generated in the flame stabilizer 31 to the filter
21 along with the heated exhaust.
[0060] Although most of the combustion gas flows from the region
surrounded by the flame stabilizer 31 toward the filter 21, some of
the gas diffused from the ejection port 42 strikes the flow
receiving portion 62. This changes the flow toward the flame
stabilizer 31. Some of the combustion gas flowing toward the flame
stabilizer 31 flows between the outer guiding portion 61 and the
outer tube 51 along the inner circumferential surface of the outer
guiding portion 61, and flows into the combustion region through
the connecting passage 53. This raises the temperature of the
combustion region as compared to a structure in which the
combustion gas is not returned to the combustion region. In this
case, the temperature of the flame stabilizer 31 can be raised from
the periphery of the flame stabilizer 31. Furthermore, most of the
combustion gas flowing to the periphery of the flame stabilizer 31
can be guided into the inner tube 41 since the outer guiding
portion 61 surrounds the entire circumferential direction of the
outer tube 51. The enlarged diameter portion 45 is formed in the
inner tube 41 of the flame stabilizer 31. Thus, the combustion gas
serving as the fluid generated by the combustion of fuel is easily
guided to the recirculation unit 32 as compared to a structure in
which the enlarged diameter portion 45 is not formed.
[0061] The air used for such combustion is supplied to the interior
of the inner tube 41 through the air passage 52, which is the gap
between the inner tube 41 and the outer tube 51. In this case, the
air flowing through the air passage 52 receives heat from the
combustion gas flowing through the gap between the outer guiding
portion 61 and the outer tube 51. Therefore, the air having a
higher temperature is supplied to the interior of the inner tube 41
compared to when the air of the air supply pipe 13a is directly
supplied to the interior of the inner tube 41. As a result, the
temperature of the interior of the inner tube 41 is raised, and the
fuel is easily burned.
[0062] In addition, the inner guiding portion 63 of the
recirculation unit 32 is formed to be cylindrical and extends from
the inner edge of the flow receiving portion 62 toward the ejection
port 42. Most of the combustion gas received by the flow receiving
portion 62 flows in either the direction toward the inner edge of
the flow receiving portion 62 or the direction toward the outer
edge of the flow receiving portion 62. In this case, most of the
fluid flowing toward the inner edge of the flow receiving portion
62 flows from the inner guiding portion 63 toward the outer edge of
the flow receiving portion 62 after striking the inner guiding
portion 63. Consequently, most of the combustion gas received by
the flow receiving portion 62 is guided to the connecting passage
53 by the outer guiding portion 61. In other words, most of the
combustion gas received by the flow receiving portion 62 is
deviated toward the outer edge of the flow receiving portion 62.
Thus, fluid is easily guided to the interior of the inner tube
41.
[0063] Furthermore, the connecting passage 53 is arranged at the
portion closer to the basal end with respect to the middle of the
flame stabilizer 31 in the axial direction, in particular, the
basal end of the flame stabilizer 31. This lengthens the flowing
passage of the combustion gas in the inner tube 41 compared to a
structure in which the connecting passage 53 is formed at the
position closer to the distal end. Therefore, the temperature of
the combustion region may be easily raised.
[0064] In particular, if the filter 21 is regenerated immediately
after the diesel engine 10 is started, the temperature of the
exhaust supplied to the exhaust purifying device 20 is not high.
Thus, the temperature of the flame stabilizer 31, and ultimately,
the temperature of the combustion region are low such that fuel is
difficult to ignite. If the combustion gas is returned to the
combustion region in such a state, the temperature of the
combustion region is raised. Thus, the fuel is easily burned.
[0065] Even if the filter 21 is regenerated after the diesel engine
10 becomes warm, combustion gas having a higher temperature than
the exhaust is returned to the combustion region. This further
raises the temperature of the flame stabilizer 31 and the
temperature of the combustion region. Therefore, the fuel is more
easily burned.
[0066] The combustion gas ejected from the ejection port 42
includes the combustion gas diffused to the periphery of the
ejection port 42 and the combustion gas substantially flowing
straight from the ejection port 42. If the recirculation unit 32 is
not included, the combustion gas diffused to the periphery of the
ejection port 42 would normally strike the housing 20h and the like
surrounding the ejection port 42 thus raising the temperature of
the housing 20h. Then, the combustion gas would strike the exhaust
in the ejection direction and the filter 21. The combustion gas
substantially flowing straight from the ejection port 42 strikes
the exhaust and the filter 21 without striking the housing 20h and
the like. The combustion gas substantially flowing straight from
the ejection port 42 is preferably used for heating to increase the
temperature rising rate of the filter 21.
[0067] With the recirculation unit 32 described above, the flow
receiving portion 62 facing the edge of the ejection port 42 in the
axial direction of the flame stabilizer 31 guides the combustion
gas substantially flowing straight from the ejection port 42 toward
the filter 21. This increases the temperature rising rate of the
filter 21 as compared to when a shielding portion such as the flow
receiving portion 62 is arranged at a position facing the ejection
port 42, that is, when the flow receiving portion 62 is arranged on
the radially inner side of the edge of the ejection port 42. The
annular flow receiving portion 62 guides the combustion gas, which
would be diffused from the ejection port 42 to strike the housing
20h, to the outer guiding portion 61 before striking the housing
20h. This increases, for example, the combustion gas guided to the
combustion region as compared to when the flow receiving portion 62
is formed only in a circumferential portion of the ejection port
42. As a result, the temperature of the combustion region can be
raised while suppressing decreases in the temperature rising rate
of the filter 21.
[0068] The fuel or the components contained in the fuel deposit on
the spark plugs 33a, 33b when fuel is burned. Such deposits contain
carbon that adversely affects the insulation of portions where
insulation is not necessary in the spark plugs 33a, 33b. As a
result, the ignition of the mixture of fuel and air with the spark
plugs 33a, 33b becomes unstable. In this regard, the temperature of
the spark plugs 33a, 33b is raised when the combustion gas flows
into the flame stabilizer 31, and the fuel and the components of
the fuel described above are less likely to deposit on the spark
plugs 33a, 33b. As a result, the ignition of the mixture with the
spark plugs 33a, 33b is stabilized, and fuel is easily burned.
[0069] As described above, the burner of the first embodiment has
the following advantages.
[0070] (1) Some of the combustion gas generated by the combustion
of fuel in the flame stabilizer 31 strikes the flow receiving
portion 62 and is guided to the outer guiding portion 61 so that a
flow from the flame stabilizer 31 toward the filter 21 is changed
to a flow from the filter 21 toward the flame stabilizer 31. The
temperature of the combustion region is raised by the flow of the
combustion gas into the combustion region. As a result, the fuel is
easily burned in the flame stabilizer 31.
[0071] (2) The flow receiving portion 62 facing the edge of the
ejection port 42 in the axial direction of the flame stabilizer 31
guides the combustion gas substantially flowing straight from the
ejection port 42 to the filter 21, and the flow receiving portion
62 receives the combustion gas diffused from the ejection port 42
and guides the gas to the outer guiding portion 61. Therefore, the
temperature of the interior of the flame stabilizer 31 is raised
while suppressing decreases in the temperature rising rate of the
filter 21.
[0072] (3) Since the outer guiding portion 61 surrounds the flame
stabilizer 31, the temperature of the flame stabilizer 31 is raised
at the periphery of the flame stabilizer 31, and most of the fluid
flowing through the periphery of the flame stabilizer 31 is guided
to the interior of the flame stabilizer 31.
[0073] (4) Some of the combustion gas received by the flow
receiving portion 62 strikes the inner guiding portion 63 and is
guided to the outer guiding portion 61. The combustion gas, of
which flow is changed to a flow from the filter 21 toward the flame
stabilizer 31, is further increased compared to when the
recirculation unit 32 includes only the outer guiding portion 61
and the flow receiving portion 62. Therefore, a larger amount of
combustion gas flows into the combustion region, and the
temperature of the interior surrounded by the flame stabilizer 31
is further raised.
[0074] (5) The air used to burn fuel receives heat from the
combustion gas while being supplied to the combustion region
through the air passage 52 in the flame stabilizer 31. Thus air
having a higher temperature is supplied to the combustion region of
the space surrounded by the flame stabilizer 31 compared to when
air is directly supplied from the air supply pipe 13a to the
combustion region. As a result, the temperature of the combustion
region is raised, and, consequently, fuel is easily burned.
[0075] (6) The connecting passage 53 is arranged at the basal end
of the flame stabilizer 31. Thus, the flow passage of the
combustion gas in the inner tube 41 is lengthened as compared to
when the connecting passage 53 is formed at a position closer to
the distal end. The temperature of the combustion region is thus
easily raised.
[0076] (7) The combustion gas ejected from the ejection port 42 is
guided by the enlarged diameter portion 45 and easily strikes the
flow receiving portion 62. This further ensures that the flow of
some of the combustion gas is changed to flow from the filter 21
toward the flame stabilizer 31.
[0077] (8) The temperature of the spark plugs 33a, 33b is raised
when the combustion gas flows into the flame stabilizer 31 so that
the fuel itself and the component of the fuel are less likely to
deposit on the spark plugs 33a, 33b. As a result, the ignition of
the mixture with the spark plugs 33a, 33b is stabilized, and the
fuel is easily burned.
Second Embodiment
[0078] A second embodiment of a burner according to the present
disclosure will now be described with reference to FIG. 4 to FIG.
6. FIG. 5 shows a cross-sectional structure taken along line 5-5 in
FIG. 4, and FIG. 6 shows a cross-sectional structure taken along
line 6-6 in FIG. 4. The burner of the second embodiment differs
from the burner of the first embodiment in the structure associated
with the supply of fuel in the burner and the structure associated
with the supply of air. Such differences will be described in
detail below, and other parts will not be described.
[0079] [Structure of Burner]
[0080] As shown in FIG. 4, a burner 70 includes a base body 70b
formed to have the shape of a circular plate. The base body 70b is
fixed to the basal end of the flame stabilizer 31, which is formed
to be cylindrical. The recirculation unit 32 is arranged on the
outer side of the flame stabilizer 31 with a gap formed with the
flame stabilizer 31, and the basal end of the recirculation unit 32
is fixed to the base body 70b.
[0081] The flame stabilizer 31 has a dual tube structure including
the inner tube 41 and the outer tube 51 extending from the base
body 70b toward the filter 21. The inner tube 41 of the flame
stabilizer 31 is formed to be cylindrical and concentric with the
recirculation unit 32, and the ejection port 42 is formed in the
distal end of the inner tube 41.
[0082] The outer tube 51 of the flame stabilizer 31 is formed to be
cylindrical and concentric with the recirculation unit 32, and
surrounds the inner tube 41 with a gap formed between the outer
tube 51 and the inner tube 41. The space between the distal end of
the inner tube 41 and the distal end of the outer tube 51 is closed
by a closing plate 54, which is formed to be annular. The air
supply pipe 13a is connected to the air passage 52, which is the
gap between the inner tube 41 and the outer tube 51. A guiding
plate 55, which is formed to be plate-shaped and which opposes the
opening of the air supply pipe 13a, is fixed to the inner
circumferential surface of the outer tube 51. The connecting
passage 53 extending through the outer tube 51 between the outer
circumferential surface and the inner circumferential surface is
formed at the basal end of the outer tube 51.
[0083] The recirculation unit 32 includes the outer guiding portion
61, the flow receiving portion 62, and the inner guiding portion
63. Further, the recirculation unit 32 is formed to be cylindrical
and surrounds the entire flame stabilizer 31. The outer guiding
portion 61 is formed to be cylindrical and extends from the base
body 70b toward the filter 21. The flow receiving portion 62, which
is formed to be annular and faces the edge of the ejection port 42,
is arranged at the distal end of the outer guiding portion 61 at a
portion closer to the filter 21 with respect to the flame
stabilizer 31. Specifically, the flow receiving portion 62 extends
inward in the radial direction over the entire circumferential
direction of the outer guiding portion 61, and is bent toward the
basal end of the outer guiding portion 61 after extending inward in
the radial direction. The inner guiding portion 63 is arranged at
the inner edge of the flow receiving portion 62. The inner guiding
portion 63 is formed to be cylindrical and extends from the inner
edge of the flow receiving portion 62 toward the base body 70b.
[0084] The end (basal portion) closer to the base body 70b of the
two ends in the inner tube 41 includes a plurality of inner
connecting passages 71, through which air flows from the air supply
pipe 13a into the inner tube 41. The inner connecting passages 71
are arranged in intervals in the circumferential direction. In the
present embodiment, the inner connecting passage 71 and the
connecting passage 53 form a connecting passage. The inner tube 41
includes a raised piece 72 in which a part of the circumferential
wall is cut and raised inward in the radial direction of the inner
tube 41 from the edge of each inner connecting passage 71.
[0085] A plurality of air supplying holes 46 extending through the
inner tube 41 are formed at a portion closer to the ejection port
42 with respect to the inner connecting passage 71 in the inner
tube 41. Each of the plurality of air supplying holes 46 guides air
from the air passage 52 to the inner tube 41.
[0086] A fuel supply unit 35 for supplying fuel into the inner tube
41 is fixed to the base body 70b. A supply port for fuel is formed
in the distal end of the fuel supply unit 35. The supply port is
arranged in the inner tube 41. A fuel pump for supplying fuel to
the engine is connected to the fuel supply unit 35, and the fuel
supply unit 35 supplies the inner tube 41 with the fuel from the
fuel pump in a vaporized state.
[0087] A connecting wall portion 73 is fixed between the inner
connecting passage 71 and the air supplying hole 46 in the inner
circumferential surface of the inner tube 41. The connecting wall
portion 73 is formed to be annular, and is bent toward the distal
end of the inner tube 41 after extending inward in the radial
direction. The outer edge of the connecting wall portion 73 is
connected over the entire circumferential direction to the inner
tube 41.
[0088] The space surrounded by the inner tube 41 is partitioned
into a first mixing chamber 81, a second mixing chamber 82, a third
mixing chamber 83, a fourth mixing chamber 84, and a fifth mixing
chamber 85.
[0089] The space between the base body 70b and the connecting wall
portion 73 in the space surrounded by the inner tube 41 is the
first mixing chamber 81. The first mixing chamber 81 receives air
from each inner connecting passage 71 and fuel from the fuel supply
unit 35. In the first mixing chamber 81, the air swirling about the
axis of the flame stabilizer 31 is mixed with the fuel injected
toward the swirling center of the air. A basal portion of a mixing
inner tube 74, which is formed to be cylindrical is connected to
the distal end of the connecting wall portion 73, and extended
through the connecting wall portion 73. In other words, the basal
portion, which is the one of the two ends of the mixing inner tube
74 that is closer to the base body 70b, is joined with the
connecting wall portion 73, and the connecting wall portion 73
closes the gap between the inner circumferential surface of the
inner tube 41 and the mixing inner tube 74. A distal portion, which
is the one of the two ends of the mixing inner tube 74 that is
closer to the ejection port 42, is open.
[0090] A support plate 75, which is formed to be annular, is fixed
to a portion closer to the ejection port 42 with respect to the
fixing area of the connecting wall portion 73 on the inner
circumferential surface of the inner tube 41. A mixing outer tube
76, which is formed to be cylindrical and which surrounds the
mixing inner tube 74, is connected to the inner circumferential
edge of the support plate 75. The distal end of the mixing outer
tube 76 is positioned closer to the ejection port 42 of the inner
tube 41 with respect to the distal end of the mixing inner tube 74,
and the closing plate 77 for closing the opening is connected to
the distal end of the mixing outer tube 76. At the support plate
75, a plurality of mixture supply ports 75a extending through the
support plate 75 between the surface at the side of the base body
70b and the surface at the side of the ejection port 42 are formed.
A metal mesh 78 covering the plurality of mixture supply ports 75a
is attached to the support plate 75 on the surface at the side of
the ejection port 42.
[0091] The second mixing chamber 82, which is a space surrounded by
the inner circumferential surface of the mixing inner tube 74, is
formed in the space surrounded by the inner tube 41. The mixture
from the first mixing chamber 81 enters the second mixing chamber
82. In the space surrounded by the inner tube 41, the third mixing
chamber 83, which is the space surrounded by the inner
circumferential surface of the mixing outer tube 76 and the closing
plate 77, is formed at a position closer to the ejection port 42
with respect to the second mixing chamber 82. The mixture from the
second mixing chamber 82 enters the third mixing chamber 83.
[0092] The fourth mixing chamber 84 is formed by a gap of the
mixing inner tube 74 and the mixing outer tube 76 in the space
surrounded by the inner tube 41. The mixture from the third mixing
chamber 83 enters the fourth mixing chamber 84. In the space
surrounded by the inner tube 41, the fifth mixing chamber 85 is
formed by a space surrounded by the inner circumferential surface
of the inner tube 41, the support plate 75, and the connecting wall
portion 73. The mixture from the fourth mixing chamber 84 enters
the fifth mixing chamber 85. In the burner 70, the first mixing
chamber 81, the second mixing chamber 82, the third mixing chamber
83, the fourth mixing chamber 84, and the fifth mixing chamber 85
form a single premixing chamber 80.
[0093] The spark plug 33 is connected to the outer guiding portion
61 of the recirculation unit 32. An ignition portion 33c formed at
the distal end of the spark plug 33 is arranged closer to the
distal end in the axial direction of the flame stabilizer 31 with
respect to the support plate 75 between the mixing outer tube 76
and the inner tube 41 in the radial direction. In the burner 70,
the gap between the inner circumferential surface of the flame
stabilizer 31 and the outer circumferential surface of the mixing
outer tube 76 forms a combustion region 90 with the space closer to
the ejection port 42 with respect to the closing plate 77 in the
inner tube 41.
[0094] As shown in FIG. 5, the guiding plate 55 is fixed to the
inner circumferential surface of the outer tube 51, and is formed
to have the shape of a plate that covers part of the opening of the
air supply pipe 13a. The guiding plate 55 is bent inward in the
radial direction from the portion fixed to the inner
circumferential surface so as to incline toward the outer
circumferential surface of the inner tube 41 as the distal end
becomes closer. The flow of air from the air supply pipe 13a toward
the outer tube 51 strikes the guiding plate 55 so that the flow
directed inward in the radial direction is changed to a flow along
the outer circumferential surface of the inner tube 41. A swirling
flow that swirls around the inner tube 41 is thereby generated
between the outer tube 51 and the inner tube 41.
[0095] As shown in FIG. 6, a plurality of raised pieces 72 formed
on the circumferential wall of the inner tube 41 is bent at an
angle covering a part of the inner connecting passage 71. The
raised piece 72 guides the air flowing from the inner connecting
passage 71 into the inner tube 41, thus generating the swirling
flow in the inner tube 41. The swirling flow generated by the
guiding plate 55 of the outer tube 51 and the swirling flow
generated by the raised piece 72 have the same swirling
direction.
[0096] [Operation of Burner]
[0097] When the fuel is burned by the burner 70, the air flowing
through the intake pipe 13 is first supplied from the air supply
pipe 13a to the air passage 52 by opening the air valve 13b. The
air flows from the distal end toward the basal end of the inner
tube 41 along the outer circumferential surface of the inner tube
41, and enters the first mixing chamber 81 from the inner
connecting passage 71. The air flowing through the air passage 52
is thereby heated.
[0098] Since the vaporized fuel is supplied from the fuel supply
unit 35 to the first mixing chamber 81, the air from the inner
connecting passage 71 and the fuel from the fuel supply unit 35 are
mixed in the first mixing chamber 81 thus generating the mixture
including air and fuel. The mixture generated by the first mixing
chamber 81 passes from the second mixing chamber 82 to the fifth
mixing chamber 85 in order, and enters the combustion region 90
through the plurality of mixture supply ports 75a formed in the
support plate 75.
[0099] Thus, the fuel mixed with air in advance is supplied to the
combustion region 90 so that the fuel is easily ignited compared to
when air and fuel are individually supplied to the combustion
region. Furthermore, the air heated in the air passage 52 is
supplied to the premixing chamber 80, so that the temperature of
the mixture supplied to the combustion region 90 is raised compared
to when the air is not heated. This easily ignites the mixture.
[0100] In the combustion region 90, the mixture is ignited by the
spark plug 33. This generates the flame F that extends toward the
ejection port 42 of the flame stabilizer 31. In the combustion
region 90, the air supplied from the air supplying hole 46 to the
combustion region 90 is mixed with the mixture. This avoids a
situation in which the mixture becomes difficult to burn due to
insufficient air.
[0101] Some of the high temperature fluid generated when burning
the mixture is guided toward the flow receiving portion 62 by the
inner guiding portion 63, and the fluid guided to the flow
receiving portion 62 flows toward the base body 70b along the inner
circumferential surface of the outer guiding portion 61. The fluid
that reaches the vicinity of the base body 70b flows from the
connecting passage 53 of the outer tube 51 into the air passage 52
so that the fluid is mixed with air in the air passage 52. The high
temperature fluid mixed with the air enters the first mixing
chamber 81 from the inner connecting passage 71 of the inner tube
41. This raises the temperature of the mixture generated in the
premixing chamber 80 compared to when the fluid does not flow into
the first mixing chamber 81.
[0102] As described above, the burner of the second embodiment has
the following advantages in addition to advantages (1) to (6) and
(8) described above.
[0103] (9) The fuel is mixed with air in advance in the premixing
chamber 80 before entering the combustion region 90. Thus, the
mixture is easily ignited compared to when the mixture is not
generated. Therefore, the fuel supplied to the combustion region 90
is easily burned.
[0104] (10) The air flowing through the air passage 52 is heated by
the flame F and the combustion gas in the combustion region 90 by
coming into contact with the outer circumferential surface of the
inner tube 41 before entering the first mixing chamber 81. Thus,
the temperature of the mixture is raised and the mixture is easily
ignited as compared to when the air is not heated.
[0105] The embodiments described above may be modified in the forms
described below.
[0106] In the first embodiment and the second embodiment, the flow
receiving portion 62 does not have to face the edge of the ejection
port 42 as long as the combustion gas ejected from the ejection
port 42 can be received. Specifically, the flow receiving portion
62 may face the region surrounded by the edge of the ejection port
42, that is, the region inward in the radial direction from the
edge of the ejection port 42 in the axial direction of the flame
stabilizer 31. Alternatively, the flow receiving portion 62 may
face the space outward in the radial direction from the edge of the
ejection port 42 in the axial direction of the flame stabilizer 31.
Even when the flow receiving portion 62 is arranged outward in the
radial direction from the edge of the ejection port 42, at least
the combustion gas spread toward the outer side in the radial
direction from the edge of the ejection port 42 of the combustion
gas ejected from the ejection port 42 is received by the flow
receiving portion. Thus, when the flow receiving portion receives
the combustion gas at the outer side of the ejection port 42, some
of the combustion gas that is ejected from the ejection port 42 is
received by the flow receiving portion and then guided to the
connecting passage 53 along the outer guiding portion 61.
[0107] In the first embodiment and the second embodiment, the flow
receiving portion 62 does not have to be annular. For example, the
outer edge of the flow receiving portion 62 may have the form of a
polygonal or elliptical ring.
[0108] In the first embodiment and the second embodiment, the flow
receiving portion 62 does not have to be annular, and may be formed
to correspond to only one circumferential portion of the ejection
port 42. Such a structure also returns the combustion gas to the
combustion region since a certain amount of the combustion gas is
received by the flow receiving portion 62. It is only required that
the shape of the flow receiving portion 62 be designed to be
suitable for the position where the combustion gas ejected from the
ejection port 42 is received, and that the shape of the flow
receiving portion 62 be designed to return the received combustion
gas to the connecting passage.
[0109] In the first embodiment and the second embodiment, the outer
guiding portion 61 does not have to have a cylindrical shape, and
may have, for example, a polygonal tubular shape with a polygonal
cross-section orthogonal to the axial direction.
[0110] In the first embodiment and the second embodiment, the outer
guiding portion 61 does not have to be tubular to surround the
flame stabilizer 31, and may be formed to correspond to only a
circumferential portion of the flame stabilizer 31. For example,
the outer guiding portion may include a plurality of plate members
formed at predetermined intervals in the circumferential direction
of the flame stabilizer 31. In such a structure, the certain amount
of combustion gas received by the flow receiving portion 62 is also
guided to the flame stabilizer 31 along the outer guiding portion
61.
[0111] In the first embodiment and the second embodiment, the inner
guiding portion 63 does not have to be cylindrical, and may have,
for example, a polygonal tubular shape in having a polygonal
cross-section orthogonal to the axial direction.
[0112] In the first embodiment and the second embodiment, the inner
guiding portion 63 does not have to be tubular, and may be formed
to correspond to only a circumferential part of the flow receiving
portion 62. In such a structure, the combustion gas is deviated
toward the outer edge of the flow receiving portion 62 at the
portion where the inner guiding portion is formed. This easily
guides the combustion gas to the flame stabilizer 31 as compared to
when the inner guiding portion is not formed.
[0113] In the first embodiment and the second embodiment, the inner
guiding portion 63 may be formed at a position closer to the outer
edge of the flow receiving portion 62 than the inner edge of the
flow receiving portion 62. In such a structure, a certain amount of
the combustion gas also flows outward in the radial direction in
the flow receiving portion 62. Thus, the combustion gas is easily
guided to the flame stabilizer 31 compared to when the inner
guiding portion is not formed.
[0114] In the first embodiment and the second embodiment, the
recirculation unit 32 may have a structure in which the inner
guiding portion 63 is omitted. In such a structure, the combustion
gas that strikes the flow receiving portion 62 is returned to the
combustion region. This raises the temperature of the combustion
region.
[0115] In the first embodiment, the position of the connecting
passage 53 is not limited to the position closer to the basal end
with respect to the middle of the flame stabilizer 31 in the axial
direction, and may be in the middle of the flame stabilizer 31 in
the axial direction or a position closer to the distal end with
respect to the middle. In such a structure, a certain amount of the
combustion gas flows into the combustion region through the
connecting passage so that the temperature of the combustion region
rises as compared to when the combustion gas does not flow into the
combustions region. Furthermore, in the second embodiment, the
position of the connecting passage 53 does not have to be at the
end (basal portion) close to the base body 70b in the outer tube
51, and may be formed at a portion closer to the ejection port
42.
[0116] In the first embodiment, a plurality of passage formation
portions 43 may be formed in intervals in the circumferential
direction at the basal end of the inner tube 41. In such a
structure, the plurality of connecting passages 53 are formed by
the upstream wall 20a and the inner tube 41. In the second
embodiment, the plurality of connecting passages 53 may be formed
in the outer tube 51 in intervals in the circumferential
direction.
[0117] In the first embodiment and the second embodiment, the
plurality of connecting passages 53 may be formed in the flame
stabilizer 31. In such a structure, the plurality of connecting
passages may be formed in predetermined intervals at the basal end
of the flame stabilizer 31, or the plurality of connecting passages
may be formed at the basal end of the flame stabilizer 31 and at
the position closer to the distal end with respect to the basal
end.
[0118] In the first embodiment and the second embodiment, the air
passage 52 does not have to be formed in the flame stabilizer 31.
In other words, the flame stabilizer 31 may be formed by a single
tube, and the air may be directly supplied to the combustion region
from the air supply pipe 13a. In such a structure, the temperature
in the combustion region is raised by the combustion gas returned
to the flame stabilizer 31 by the recirculation unit 32 so that the
fuel is easily burned.
[0119] In the first embodiment, the flame stabilizer 31 may have a
structure in which the enlarged diameter portion 45 is omitted. In
such a structure, some of the combustion gas ejected from the
ejection port formed in the constant diameter portion 44 strikes
the flow receiving portion 62. Thus, some of the combustion gas is
returned to the combustion region by the recirculation unit 32.
[0120] The structure of the flame stabilizer and the structure of
the recirculation unit described in the first embodiment, the
second embodiment, or a modification may be combined.
[0121] In the first embodiment and the second embodiment, an
ignition source for combusting fuel is not limited to the spark
plugs 33a, 33b, and may be a glow plug, a laser spark device, a
plasma spark device, and the like, or may be a combination of two
or more of these devices. The ignition unit only needs to be
capable of igniting the mixture of fuel and air.
[0122] In the first embodiment, the housing 20h, the inner tube 41,
the outer tube 51, and the recirculation unit 32 are not limited to
a cylindrical shape and may have, for example, a polygonal tubular
shape having a polygonal cross-section orthogonal to the axial
direction, and in the second embodiment, may have a polygonal
tubular shape having a polygonal cross-section orthogonal to the
axial direction in the inner tube 41 and the outer tube 51.
[0123] In the second embodiment, the air supplying hole 46 formed
in the inner tube 41 may be omitted, that is, a structure in which
the air used for the combustion of fuel is supplied to the
combustion region 90 through only the premixing chamber 80 may be
adopted.
[0124] In the second embodiment, the air supply pipe 13a may be
connected to the base body 70b. In other words, the air used for
the combustion of fuel may enter the premixing chamber 80 without
passing through the air passage 52 formed in the flame stabilizer
31. In this case, the outer tube 51 and the closing plate 54 of the
flame stabilizer 31 may be omitted.
[0125] In the second embodiment, the position of the ejection port
42 of the flame stabilizer 31 and the distal portion of the outer
guiding portion 61 may be further separated in the axial direction
of the flame stabilizer 31.
[0126] In the second embodiment, the distal end of the flame
stabilizer 31 may have an enlarged diameter like in the first
embodiment. Such a structure obtains advantage (7) of the first
embodiment.
[0127] In the second embodiment, the connecting wall portion 73,
the mixing inner tube 74, the support plate 75, the mixing outer
tube 76, and the closing plate 77, which are the partitioning
portions partitioning the premixing chamber 80 and the combustion
region 90, may be flat plates arranged at the inner side of the
inner tube 41 orthogonal to the axial direction of the inner tube
41. Alternatively, the partitioning portions may include, for
example, only the support plate 75, the mixing outer tube 76, and
the closing plate 77. In this case, the connecting wall portion 73
and the mixing inner tube 74 are omitted.
[0128] In other words, the partitioning portions for partitioning
the premixing chamber 80 and the combustion region 90 merely needs
to be a member for partitioning the space in which the mixture is
generated and the space in which the mixture is ignited in the
space defined by the inner tube 41.
[0129] The partitioning portions formed by the connecting wall
portion 73, the mixing inner tube 74, the support plate 75, the
mixing outer tube 76, and the closing plate 77 described above
result in a complicated passage that connects the space in which
the mixture is generated and the space in which the mixture is
ignited. This increases the rate at which the fuel and air are
mixed. Thus, the partitioning portion is preferably formed as
described above.
[0130] In the first embodiment and the second embodiment, instead
of the filter 21, any of a variety of catalysts used for the
purification of the exhaust may be arranged at the downstream side
of the burner 30. Alternatively, the filter 21 and a catalyst may
be connected in parallel at the downstream side of the burner 30,
and the combustion gas generated by the combustion in the burner 30
and the heated exhaust may be delivered to both of the filter 21
and the catalyst.
[0131] In the first embodiment and the second embodiment, the
burners 30, 70 do not have to be arranged in front of the filter 21
in the exhaust pipe 18 and may be arranged behind the filter 21 in
the exhaust pipe 18.
[0132] In the first embodiment, the fuel injection nozzle 34 may be
formed to eject vaporized fuel.
[0133] In the first embodiment, the fuel injected from the fuel
injection nozzle 34 may be supplied from a common rail instead of
the fuel pump. Alternatively, a fuel pump for supplying fuel to the
fuel injection nozzle 34 may be separately provided.
[0134] In the second embodiment, the fuel supply unit 35 may be
formed to inject non-vaporized fuel.
[0135] In the first embodiment and the second embodiment, the air
used for the combustion of fuel in the burners 30, 70 does not have
to be the air flowing through the intake pipe 13, and may be, for
example, air flowing through a pipe connected to a brake air tank
or air supplied from a blower to the burners 30, 70.
[0136] The engine including the exhaust purifying device 20 is not
limited to the diesel engine 10 and may be a gasoline engine.
DESCRIPTION OF REFERENCE SYMBOLS
[0137] 10 diesel engine [0138] 11 cylinder block [0139] 11a
cylinder [0140] 12 intake manifold [0141] 13 intake pipe [0142] 13a
air supply pipe [0143] 13b air valve [0144] 14 air cleaner [0145]
15 compressor [0146] 16 exhaust manifold [0147] 17 EGR pipe [0148]
18 exhaust pipe [0149] 19 turbine [0150] 20 exhaust purifying
device [0151] 20a upstream wall [0152] 20h housing [0153] 21 filter
[0154] 30, 70 burner [0155] 31 flame stabilizer [0156] 32
recirculation unit [0157] 33, 33a, 33b spark plug [0158] 33c
ignition portion [0159] 34 fuel injection nozzle [0160] 35 fuel
supply unit [0161] 41 inner tube [0162] 42 ejection port [0163] 43
passage formation portion [0164] 44 constant diameter portion
[0165] 45 enlarged diameter portion [0166] 46 air supplying hole
[0167] 51 outer tube [0168] 52 air passage [0169] 53 connecting
passage [0170] 54, 77 closing plate [0171] 55 guiding plate [0172]
61 outer guiding portion [0173] 62 flow receiving portion [0174] 63
inner guiding portion [0175] 70b base body [0176] 71 inner
connecting passage [0177] 72 raised piece [0178] 73 connecting wall
portion [0179] 74 mixing inner tube [0180] 75 support plate [0181]
75a mixture supply port [0182] 76 mixing outer tube [0183] 78 metal
mesh [0184] 80 premixing chamber [0185] 81 first mixing chamber
[0186] 82 second mixing chamber [0187] 83 third mixing chamber
[0188] 84 fourth mixing chamber [0189] 85 fifth mixing chamber
combustion 90 region [0190] F flame [0191] TC turbo charger
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