U.S. patent application number 11/380767 was filed with the patent office on 2007-03-15 for counterflow fuel injection nozzle in a burner-boiler system.
Invention is credited to Normand Brais, Normand Bujold, Ad de Pijper, Bernard Labelle, Eugene Showers, Daniel J. Willems.
Application Number | 20070057090 11/380767 |
Document ID | / |
Family ID | 33555360 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070057090 |
Kind Code |
A1 |
Labelle; Bernard ; et
al. |
March 15, 2007 |
Counterflow Fuel Injection Nozzle in a Burner-Boiler System
Abstract
A counterflow fuel injection nozzle for injecting fuel is
disclosed. The nozzle includes a nozzle wall having an interior
surface that defines a nozzle interior, the interior for receiving
a fuel therein. The nozzle further has a fuel passageway formed in
the nozzle wall for distributing the fuel from the interior to a
location exterior of the nozzle, the fuel distributed to the
exterior location in a fuel flow injection direction. An airstream
is provided in a prevailing air flow direction in the location
exterior of the nozzle. At least one vector component of the fuel
flow injection direction opposes at least one vector component of
the prevailing air flow direction. In this manner, by distributing
fuel into an air flow at a counterflow angle, improved control of
mixing of the fuel in the air is achieved. The counterflow nozzle
may be included as part of a new burner or as a retrofit to
existing burners in order to incorporate counterflow mixing.
Advantageously, burner turndown ratios and stability are enhanced
through the use of the counterflow fuel injection nozzles with
burners that use FGR (i.e., have lower O.sub.2 in combustion air
supplied to the burner).
Inventors: |
Labelle; Bernard; (Quebec,
CA) ; Brais; Normand; (Quebec, CA) ; Bujold;
Normand; (Quebec, CA) ; Willems; Daniel J.;
(Hartland, WI) ; de Pijper; Ad; (Winnebago,
IL) ; Showers; Eugene; (Monroe, WI) |
Correspondence
Address: |
WHYTE HIRSCHBOECK DUDEK S C
555 EAST WELLS STREET
SUITE 1900
MILWAUKEE
WI
53202
US
|
Family ID: |
33555360 |
Appl. No.: |
11/380767 |
Filed: |
April 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10857399 |
May 28, 2004 |
|
|
|
11380767 |
Apr 28, 2006 |
|
|
|
60474470 |
May 31, 2003 |
|
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|
Current U.S.
Class: |
239/418 |
Current CPC
Class: |
F23C 7/004 20130101;
F23D 14/02 20130101; F23C 2202/30 20130101; F23D 14/58
20130101 |
Class at
Publication: |
239/418 |
International
Class: |
F23D 11/10 20060101
F23D011/10 |
Claims
1. A counterflow fuel injection nozzle for injecting a gaseous
fuel, the nozzle comprising: a nozzle wall having an interior
surface that defines a nozzle interior, the interior for receiving
a fuel therein, the nozzle further having a plurality of fuel
passageways formed in the nozzle wall for distributing the fuel
from the interior to a location exterior of the nozzle, the fuel
distributed to the exterior location in a fuel flow injection
direction; wherein, when an airstream is provided in a prevailing
air flow direction in the location exterior of the nozzle, at least
one vector component of the fuel flow injection direction opposes
at least one vector component of the prevailing air flow
direction.
2. The counterflow fuel injection nozzle of claim 1 wherein at
least one of the fuel passageways terminates in an opening having a
diameter in a range of between about 0.063 inches to about 0.189
inches.
3. The counterflow fuel injection nozzle of claim 2 wherein the
opening has a diameter of about 0.1875 inches.
4. The counterflow fuel injection nozzle of claim 3 where in the
nozzle is used to generate steam and/or hot water.
5. The counterflow fuel injection nozzle of claim 4 wherein the
nozzle is used in a combustion apparatus.
6. A combustion apparatus comprising: a plurality of radially
disposed lances, each of the lances connected to at least one of a
plurality of counterflow fuel injection nozzles for injecting a
gaseous fuel; wherein each of the fuel injection nozzles includes:
a nozzle wall having an interior surface that defines a nozzle
interior, the interior for receiving a fuel therein, and each of
the nozzles further includes a plurality of fuel passageways formed
in the nozzle wall for distributing the fuel from the interior to a
location exterior of each nozzle, the fuel distributed to the
exterior location in a fuel flow injection direction; and wherein,
when an airstream is provided in a prevailing air flow direction in
the location exterior of the each nozzle, at least one vector
component of the fuel flow injection direction opposes at least one
vector component of the prevailing air flow direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-In-Part of U.S. Ser. No.
10/857,399, filed May 28, 2004, pending, which also claims the
benefit of the filing date of U.S. application Ser. No. 60/474,470,
filed on May 31, 2003.
FIELD AND BACKGROUND OF THE INVENTION
[0002] The field of the invention relates generally to fuel
injection nozzles, and more particularly, to a counterflow fuel
injection nozzle.
[0003] Burners are used in boilers, heaters, and other applications
for the conversion of fuel to heat. The heat is then transferred to
make hot water, steam, and/or warm air, or to create power,
depending upon the application. In a burner-boiler system (e.g.,
firetube and commercial and industrial watertube boilers), fuel is
typically injected through nozzles to create a flame. The fuel is
combined with air flowing around or adjacent the nozzle.
Ultimately, the fuel is ignited to create a flame, with a goal
being to maximize the conversion of the fuel that is burned during
this combustion process so as to achieve complete combustion. The
manner in which the fuel is injected (i.e., its direction,
velocity, and interaction with other fluid streams) into the air
stream affects the flame profile or shape and thus greatly
determines the completeness of the combustion and heat release into
the furnace. The injection method affects the overall geometry and
physical characteristics of the nozzle itself. For example, the
fuel is typically injected through passageway(s) formed in the
nozzle, and more particularly, the nozzle body. These physical
characteristics include the width or diameter, spacing, and angling
or pitch of the particular passageway(s) or channel(s).
[0004] It is a continuing design goal to control mixing (e.g.,
quality, uniformity, rate, etc.) of the fuel and air by the burner
so that air and fuel are evenly mixed. Variations in the width,
spacing and pitch of the passageways of the nozzle used for
distributing fuel from the nozzle yield varied mixing results,
flame profiles, flame locations and overall combustion performance
factors. It has been found that angled injection passageways that
inject the fuel in a counterflow fashion contribute positively to
the aforementioned factors. By "counterflow" it is meant that the
fuel is injected into a flow of air such that at least one vector
component of the fuel flow opposes at least one vector component of
the air flow. Therefore, it would be desirable, in a burner using a
gaseous fuel (e.g, natural gas), to be able to improve control of
the mixing of the fuel with air by introducing the fuel into the
air in counterflow fashion.
BRIEF SUMMARY OF THE INVENTION
[0005] Disclosed herein is a counterflow fuel injection nozzle for
injecting fuel, the nozzle comprising: a nozzle wall having an
interior surface that defines a nozzle interior. The interior for
receiving a fuel therein, the nozzle further having a fuel
passageway formed in the nozzle wall for distributing the fuel from
the interior to a location exterior of the nozzle, the fuel
distributed to the exterior location in a fuel flow injection
direction. When an airstream is provided in a prevailing air flow
direction in the location exterior of the nozzle, at least one
vector component of the fuel flow injection direction opposes at
least one vector component of the prevailing air flow
direction.
[0006] Other objects, aspects, and advantages of the invention will
be apparent upon a thorough reading of the detailed description
below along with the drawings,
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Embodiments of the invention are disclosed with reference to
the accompanying drawings and are for illustrative purposes only.
The invention is not limited in its application to the details of
construction or the arrangement of the components illustrated in
the drawings. The invention is capable of other embodiments or of
being practiced or carried out in other various ways. Like
reference numerals are used to indicate like components. In the
drawings:
[0008] FIG. 1 is perspective partially cut-away view of a burner
incorporating an embodiment of a counterflow fuel injection nozzle
of the present invention;
[0009] FIG. 1a is a front view of a burner incorporating an
embodiment of the counterflow fuel injection nozzle of the present
invention;
[0010] FIG. 2a is a side sectional view taken along line 2a-2a of
FIG. 1a;
[0011] FIG. 2b is a diagram schematically illustrating the concept
of counterflow with respect to a representation of the present
inventive counterflow fuel injection nozzles;
[0012] FIG. 2c is a representation of various hole and distance
parameters associated with the counterflow fuel injection nozzle
illustrating the parameters that affect the interaction of fuel
jets from adjacent nozzles;
[0013] FIG. 2d is a graphical representation of various penetration
depths of the fuel and overall fuel distribution patterns
associated with the present invention;
[0014] FIG. 3 is an enlarged sectional view taken along line 3-3 of
FIG. 2a;
[0015] FIG. 4 is a perspective view of one embodiment of the
counterflow fuel injection nozzle according to one aspect of the
present invention;
[0016] FIG. 5 is a bottom sectional view taken along line 5-5 of
FIG. 3;
[0017] FIG. 6 is a perspective view of another embodiment of the
counterflow fuel injection nozzle according to one aspect of the
present invention;
[0018] FIG. 7 is a side sectional view of the counterflow fuel
injection nozzle of FIG. 6;
[0019] FIG. 8 is a bottom sectional view taken along line 8-8 of
FIG. 7 and illustrating exemplary counterflow injection angles;
[0020] FIG. 9 is a perspective view of another embodiment of the
counterflow fuel injection nozzle according to one aspect of the
present invention;
[0021] FIG. 10 is a side sectional view of the counterflow fuel
injection nozzle of FIG. 9;
[0022] FIG. 11 is a front sectional view taken along line 11-11 of
FIG. 10 and illustrating exemplary angular spacing of the fuel
injection holes;
[0023] FIG. 12 is a perspective view of another embodiment of the
counterflow fuel injection nozzle according to one aspect of the
present invention;
[0024] FIG. 13 is a side sectional view of the counterflow fuel
injection nozzle of FIG. 12;
[0025] FIG. 14 is a partial side sectional view of another
embodiment of the counterflow fuel injection nozzle according to
one aspect of the present invention; and
[0026] FIG. 15 is a perspective view of the counterflow fuel
injection nozzle of FIG. 14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] In the Figures, like numerals are employed to designate like
parts through the drawings, and various pieces of equipment, such
as valves, fittings, pumps, and the like, are omitted so as to
simplify the description of the invention. However, those skilled
in the art will realize that such conventional equipment can be
employed as desired. In addition, although the invention is
applicable to various fuel-burning equipment, it will be discussed
for purposes of illustration in connection with a steam or hot
water boiler.
[0028] FIG. 1 is perspective partially cut-away view of a burner 1
incorporating an embodiment of a counterflow fuel injection nozzle
2 of the present invention. Burner 1 can receive a gaseous fuel
(e.g., propane, natural gas, etc.) from a fuel source (not shown)
via a fuel line or pipe (also not shown) and delivery within the
burner via lance 14. Total combustion air flow is indicated by
arrow 3, with primary air 4, secondary air 5, and tertiary air 6
flowing through other paths (as directed at the burner entrance,
for example, around a diffuser 7 and between injection nozzles) to
promote complete combustion. The air flows may have, in addition to
air, flue gas products (FGR). In general, the O.sub.2 levels are
lower in flue gas products than in air. Therefore, more air may be
necessary in the primary, secondary or tertiary air flows to
achieve the necessary oxygen levels required for complete
combustion. Oxygen levels can preferably be in the range of 11-21%,
more preferably in the 15-21% range, and most preferably in the
16-19% range.
[0029] FIG. 1a is a front view of a burner incorporating an
embodiment of the counterflow fuel injection nozzle of the present
invention and FIG. 2a is a side elevational view taken along line
2a-2a of FIG. 1a. Referring to FIGS. 1a and 2a, fuel is introduced
into the burner 10 at a number of locations via manifold 11. More
specifically, fuel is introduced via a plurality of radially
disposed fuel lines or lances 14. In addition, central injection
pipe 13 is used for distributing fuel via nozzles 15 to create a
flame in the center of the burner. Burner 10 further includes a
diffuser (also called a "swirler"), generally referred to by
numeral 18, having blades 20. Tertiary air is introduced into
burner 10, also indicated by numeral 6, and diffuser 18 imparts a
rotating motion to the air so as to increase mixing of the air and
the fuel. The radially disposed lances 14 terminate with injection
nozzles 16, also referred to herein as simply "injectors" or
"nozzles". The distance 19 between the head 17 of nozzle 16 and the
beginning of the diffuser plane area 21 is an important factor for
successful application of the nozzle 16 as it will affect mixing
capabilities of the fuel and air. The gap between nozzle 16 and
outer ring 25, as indicated by arrow 27, is also important for
mixing capabilities.
[0030] Primary, secondary and tertiary air is introduced into the
burner 10 as shown. In the embodiment shown, the "prevailing air
flow direction" corresponds to an air flow direction in which the
air travels from a location generally upstream of the fuel
injectors to a location generally downstream of the fuel injectors.
The flow of air can be influenced by structures or "bluff bodies"
within the burner itself (e.g., the diffuser, manifolds, fuel
lines, etc.). As will be described in greater detail below, and as
shown in FIG. 1, at least a portion of the air flow is directed or
distributed past the diffuser and generally along or past the
nozzles 16.
[0031] FIG. 2b is a diagram schematically illustrating the concept
of counterflow with respect to a representation of the present
inventive counterflow fuel injection nozzle. As shown, fuel flows
into the nozzle 510 in an initial fuel flow direction 518 and flows
into the interior 514 of the nozzle. Fuel is distributed from the
nozzle interior 514 along a fuel flow injection direction 520
(F.sub.fuel). The fuel is typically injected at a preferred
pressure of up to 20 psig. "Fuel flow injection angle" is that
angle at which the fuel is injected out of the counterflow fuel
injection nozzle, and more specifically, the nozzle interior, via
apertures, holes, or openings 516a-b to a location exterior of the
nozzle. Fuel flow injection direction is determined by the fuel
flow injection angle .theta. at which fuel is distributed from the
nozzle interior. The trajectory is determined by the angle, as well
as the fuel and the air velocity. As shown, the angle is measured
from a plane that is normal or perpendicular to the surface of the
nozzle. Fuel flowing along fuel flow injection direction 520
includes a perpendicular flow vector component 522 ##STR1## and a
counterflow vector component 524 ##STR2## By "perpendicular" it is
meant that the vector component is perpendicular to the prevailing
air flow direction, and by "counterflow" it is meant that the
vector component opposes the prevailing air flow direction.
[0032] To promote mixing of fuel and air, the fuel is injected
along the fuel injection direction 520 into air flowing in a
prevailing air flow direction 526 (F.sub.air). Mixing typically
occurs at a location exterior of the nozzle. It is noted that the
fuel flow injection direction vector is shown in schematic fashion
to illustrate the fuel flow injection angle with greater clarity,
but that the fuel flow trajectory takes on a more complex path
(i.e., it curves or swirls) due to the injection of the fuel into
the prevailing air flow and as the distance the fuel travels from
the nozzle increases. This more complex path is indicated by the
arrow 525.
[0033] Fuel flows in the fuel flow injection direction such that is
generally angled with respect to the prevailing air flow direction
resulting in a counterflow angle .DELTA., which is measured with
respect to the prevailing air flow direction. A "counterflow angle"
exists when at least one vector component (i.e., a counterflow fuel
vector component) of the fuel flow injection direction is opposite
at least one vector component of the prevailing air flow direction
(i.e., a counterflow air vector component). As shown schematically,
counterflow fuel vector component 524 opposes or is opposite (and
thus flows counter to) at least one counterflow air vector
component of the prevailing air flow direction 526. A significant
purpose for distributing fuel into an air flow to create a
counterflow angle is to achieve, or to substantially achieve,
complete mixing of the fuel in the air. Preferably, the spectrum of
fuel flow injection angles .theta. ranges from about 15 degrees to
about 90 degrees (i.e., with 90 degrees meaning complete
counterflow). In one preferred embodiment, the counterflow angle is
about 30 degrees.
[0034] FIG. 3 is an enlarged sectional view taken along line 3-3 of
FIG. 2a, in particular, illustrating a sectional view of nozzle 16
according to one aspect of the present invention in greater detail.
FIG. 4 is a perspective view of one embodiment of the counterflow
fuel injection nozzle according to one aspect of the present
invention. Injection nozzle 16 includes a nozzle body 28. And FIG.
5 is a bottom sectional view taken along line 5-5 of FIG. 3.
[0035] Referring to FIGS. 3-5, the nozzle body 28 has a nozzle wall
30, and the nozzle wall 30 defines a nozzle interior 32. As shown,
nozzle 16 is generally "T"-shaped. It is nozzle interior 32 that
receives the fuel to be distributed and ultimately injected into to
the airstream to produce a flame. Since nozzle interior 32 acts as
a fuel conduit, the hole shape, hole diameters, hole distribution
and injection angles all contribute to how the fuel is distributed
throughout the nozzle interior 32. The embodiment shown is
representative only, and it is contemplated that other shapes,
geometric features and body outlines could be suitably employed.
That is, the nozzle may have other particularized curves, tapers,
angles, and interior surface and interior geometries and still
accomplish the objectives of the injection nozzle 16. Also, any
suitable materials may be used in the construction of injection
nozzle 16, although stainless steel is one preferred material,
among others. Interior surface 34 of nozzle wall 30 defines nozzle
interior 32 into which fuel is received from fuel line 14. Various
means of connection between the fuel line 14 and the injection
nozzle 16 are possible. Nozzle body 28 further includes a series of
fuel passageways 40 terminating in holes or openings 42 formed in
the nozzle wall for distributing the fuel from the interior.
[0036] Accordingly, fuel flows from the nozzle interior 32 through
the passageways 40 and out of the nozzle 16 via holes 42 into an
air flow (see FIGS. 1-2). It is contemplated that the size, shape,
and placement of the holes and passageways can be varied to achieve
the desired mixing effect (i.e., mixing between the air flow and
the fuel injected into the air). The size of the nozzle holes are
critical, since, if the holes are too small "fouling" and other
similar problems may occur. One factor in determining the
appropriate size, shape and placement of holes and passages is the
position of the nozzle relative the air flow. Another factor is the
geometry of the nozzle itself. Hole placement can be selected to
promote mixing by distributing fuel into the prevailing air flow.
The result is that the air is entrained (carried in a current)
within the fuel to achieve better mixing. Ultimately, the goal is
to achieve uniform mixing, and it has been found that more uniform
mixing results from a wide dispersal of fuel into an air flow.
[0037] In the embodiment illustrated in FIGS. 3-5, representative
passageways and placement of holes are shown in a representative
nozzle. Fuel is injected along a fuel injection direction 40.
Representative fuel injection trajectories are illustrated by
arrows 44. More specifically, in one embodiment, the passageways
can be cylindrical and the holes can be round. Although any hole
size is contemplated, in one embodiment, the holes can be sized to
have a diameter in a range of from about 0.0625 inches to about
0.141 inches. In one embodiment, the holes can be spaced apart, as
measured from their respective centers, from about 0.325 to about
0.75 inches, with an exemplary hole distance of 0.5 inches
apart.
[0038] It is a design goal to select the size, shape and placement
of the holes in the nozzle to minimize, or substantially eliminate,
interference between the holes (e.g., one fuel injection direction
crossing, in whole or in part, another fuel injection direction).
As shown in FIG. 2c, for a given nozzle N, the distance between the
holes of an exemplary nozzle is L and the diameter of the holes is
D. The ratio L/D will define the interaction between adjacent
holes. The diameter of the holes will determine the penetration
depth of the fuel (gas) and overall fuel distribution patterns. L
determines whether the adjacent fuel jets result in mixing or
combining of the fuel streams. As shown in FIG. 2d, exemplary
penetration depth of fuel and fuel distribution patterns x1 and x2
are illustrated for 2 holes y and z of different hole diameters. It
is contemplated that the variations of size, shape and placement of
the holes can be from nozzle to nozzle (i.e., for a given nozzle
the holes and spacings are identical), or the size, shape and
placement can vary from hole to hole. In a preferred embodiment,
the ratio of L to D is about 5. The interaction between adjacent
nozzles (in addition to staggering of holes) can be an effective
means to effect fuel jet interaction.
[0039] In general, it can be said that the counterflow angle (i.e.,
the angle created by the fuel flow injection direction with respect
to the prevailing air flow direction) effects mixing downstream of
the holes. It has been found that ideal mixing conditions occur
when the counterflow angle is such that the fuel flow direction is
not entirely opposed to the prevailing air flow direction. The
counterflow angle also effects the air/fuel mixing location and
permits control over whether mixing occurs more or less downstream
of the nozzles. This can be advantageous for a variety of reasons.
For example, by keeping the mixing of the air and fuel further
downstream of the nozzles, the flame can be created further
downstream, and the nozzle can be protected from exposure to high
levels of heat. This can serve to prevent the nozzles from burning
out prematurely. Also, the size, number and placement of passages
and holes in the nozzle body permits flame sculpting (also called
flame shaping, or flame forming) to achieve optimum mixing in
relation to the furnace geometry. In general, it has been found
that when the conditions approach "complete counterflow" (i.e.,
when the fuel and air trajectories are completely opposed to each
other), better mixing can occur, although less control of the
mixing will be achieved, since the paths of the trajectories will
be unpredictable. Also, counterflow angle selection is dependant
upon such conditions as the burner air flow distribution, direction
and velocity.
[0040] FIG. 6 is a perspective view of another embodiment of a
counterflow fuel injection nozzle according to one aspect of the
present invention. FIG. 7 is a side sectional view of the
counterflow fuel injection nozzle of FIG. 6 and FIG. 8 is a bottom
sectional view taken along line 8-8 of FIG. 7. FIGS. 6-8 also
illustrate exemplary counterflow injection angles.
[0041] Referring to FIGS. 6-8, the nozzle body 128 has a nozzle
wall 130, and the nozzle wall 130 defines a nozzle body interior
132. As shown, nozzle 1 16 is generally "Truncated T-shaped" in
that it is truncated when compared to the embodiment of FIGS. 3-5.
It is nozzle body interior 132 that receives the fuel to be
distributed and ultimately injected in the airstream to produce a
flame. Since nozzle body interior 132 acts as a fuel conduit, the
hole shapes, as with the other embodiments, the hole diameters,
hole distribution and injection angles all contribute to how the
fuel is distributed throughout the nozzle interior 132. The
embodiment shown is representative only, and it is contemplated
that other shapes, geometric features and body outlines could be
suitably employed. Also, any suitable materials may be used in the
construction of injection nozzle 116, although stainless steel is
one preferred material, among others. Interior surface 134 of
nozzle wall 130 defines nozzle interior 132 into which fuel is
received from fuel line 114. Fuel line 114 includes an optional
threaded portion 136 for threaded insertion into a mating threaded
portion 138 of interior surface 134 if a threaded connection is
desired. Although a threaded engagement is shown and preferred, it
is contemplated that other means of connection between the fuel
line 114 and the injection nozzle 116 are possible. Nozzle body 128
further includes a series of fuel passageways 140 terminating in
holes or openings 142 formed in the nozzle wall for distributing
the fuel from the interior.
[0042] Accordingly, fuel flows from the nozzle interior 132 through
the passageways 140 and out of the nozzle 1 16 via holes 142 into
an air flow (again, see FIGS. 1-2). It is contemplated that the
size, shape, and placement of the holes and passageways can be
varied to achieve the desired mixing effect (i.e., mixing between
the air and the fuel injected into the air). Again, hole placement
will be selected to promote mixing by distributing fuel into the
prevailing air flow.
[0043] In the embodiment illustrated in FIGS. 6-8, representative
passageways and placement of holes are shown in a representative
nozzle. Fuel is injected along representative fuel injection
directions 144.
[0044] The size and placement of the various passageways and holes
are similar to those described in detail above with respect to
FIGS. 3-5.
[0045] FIG. 9 is a perspective view of another embodiment of the
counterflow fuel injection nozzle according to one aspect of the
present invention. One design parameter of the embodiment of FIG. 9
is the limited footprint shown, such that the nozzle shown could be
incorporated into smaller burners, particularly where the insertion
of a larger area T or other shaped nozzle would not fit properly
into the space provided. FIG. 10 is a side sectional view of the
counterflow fuel injection nozzle of FIG. 9. FIG. 11 is a front
sectional view taken along line 11-11 of FIG. 10. FIGS. 9-11
illustrate exemplary fuel flow injection angles and angular hole
spacing.
[0046] Referring to FIGS. 9-11, the nozzle body 228 has a nozzle
wall 230, and the nozzle wall 230 defines a nozzle body interior
232. As shown, nozzle 216 includes several contours which define a
primary centralized circumferentially disposed notch or groove 233
which defines a surface 235. The shape of the nozzle is generally
termed herein "mushroom-shaped". It is nozzle body interior 232
that receives the fuel to be distributed and ultimately injected in
the airstream to produce a flame. Since nozzle body interior 232
acts as a fuel conduit, the particularized curves, tapers, angles
and surface and interior geometry of the injection nozzle 216 will
dictate how the fuel is distributed throughout the nozzle body
interior 232. The embodiment shown is representative only, and it
is contemplated that other shapes, geometric features and body
outlines could be suitably employed. Also, any suitable materials
may be used in the construction of injection nozzle 216, although
steel is one preferred material, among others. Interior surface 234
of nozzle wall 230 defines nozzle interior 232 into which fuel is
received from fuel line 214. Fuel line 214 includes threaded
portion 236 for threaded insertion into a mating threaded portion
238 of interior surface 234. Although a threaded engagement is
shown and preferred, it is contemplated that other means of
connection between the fuel line 214 and the injection nozzle 216
are possible. Nozzle body 228 further includes a series of fuel
passageways 240 terminating in holes or openings 242 formed in the
nozzle wall for distributing the fuel, and more particularly, the
holes are formed in the surface 235 of primary centralized
circumferentially disposed notch or groove 233.
[0047] Accordingly, fuel flows from the nozzle interior 232 through
the passageways 240 and out of the nozzle 216 via holes 242 into an
air flow (again, see FIGS. 1-2). It is contemplated that the size,
shape, and placement of the holes and passageways can be varied to
achieve the desired mixing effect. Here too, hole placement will be
selected to promote mixing by distributing fuel into the prevailing
air flow.
[0048] In the embodiment illustrated in FIGS. 9-11, representative
passageways and placement of holes are shown in a representative
nozzle. Fuel is injected along a fuel injection direction 244.
Representative fuel injection trajectories are illustrated by
arrows 244.
[0049] The size and placement of the various passageways and holes
are similar to those described in detail above with respect to
FIGS. 3-5.
[0050] FIG. 12 is a perspective view of another embodiment of the
counterflow fuel injection nozzle 416 according to one aspect of
the present invention. FIG. 13 is a side sectional view of the
counterflow fuel injection nozzle 416 of FIG. 12. FIGS. 12-13 also
illustrate fuel injection and counterflow fuel injection
trajectories.
[0051] Referring to FIGS. 12-13, the nozzle body 428 has a nozzle
wall 430, and the nozzle wall 430 defines a nozzle interior 432. It
is nozzle body interior 432 that receives the fuel to be
distributed and ultimately injected into the airstream to produce a
flame. Since nozzle body interior 432 acts as a fuel conduit, the
particularized curves, tapers angles and surface and interior
geometry of the injection nozzle 416 will dictate how the fuel is
distributed throughout the nozzle body interior 432. Here too, the
embodiment shown is representative only, and it is contemplated
that other shapes, geometric features and body outlines could be
suitably employed. Here again, any suitable materials may be used
in the construction of injection nozzle 416, although stainless
steel is one preferred material, among others.
[0052] Interior surface 434 of nozzle wall 430 defines nozzle
interior 432 into which fuel is received from fuel line 414. Fuel
line 414 includes threaded portion 436 for threaded insertion into
a mating threaded portion 438 of interior surface 434. Although a
threaded engagement is shown and preferred, it is contemplated that
other means of connection between the fuel line 414 and the
injection nozzle 416 are possible. Nozzle body 428 further includes
a series of fuel passageways 440 terminating in holes or openings
442 formed in the nozzle wall 430, and more specifically, groove
433, for distributing the fuel. Groove 433 prevents air from
shearing off the gas exiting the holes and permitting gas to
develop into a jet stream, resulting in more consistent mixing.
[0053] Fuel flows from the nozzle interior 432 through the
passageways 440 and out of the nozzle 416 via holes 442 into an air
flow (again, see FIGS. 1-2). It is contemplated that the size,
shape, and placement of the holes and passageways can be varied to
achieve the desired mixing effect. Again, hole placement can be
selected to promote mixing by distributing fuel into the prevailing
air flow.
[0054] In the embodiment illustrated in FIGS. 12-13, representative
passageways and placement of holes are shown in a representative
nozzle. Fuel is injected along a fuel injection direction 444.
[0055] In one embodiment of the counterflow fuel injection nozzles
depicted in FIGS. 12 and 13, the passageways can be cylindrical and
the holes can be round. Although any hole size is contemplated, in
one embodiment, the holes can be sized to have a diameter in a
range of from about 0.0625 inches to about 0.141 inches. Angular
spacing of the holes ranges, in one embodiment, from between about
45 degrees to about 60 degrees. It is contemplated that variations
in size, shape and placement can be on a hole by hole and/or nozzle
by nozzle basis. It is understood, however, that it is a design
goal to select the size, shape and placement of the holes to
minimize, or eliminate interference between the fuel flow
trajectories from the holes (e.g., one fuel injection direction
crossing, in whole or in part, another fuel injection
direction).
[0056] Hole pattern (i.e, the number and position of the holes), as
well as hole size (e.g., as determined by hole diameter) can be
varied. In this manner, mixing of the air and fuel can be
accomplished so as to control and achieve complete or substantially
complete combustion, a hallmark of the present invention.
[0057] Referring now to FIGS. 14 and 15, another embodiment of the
counterflow fuel injection nozzle 500 according to one aspect of
the present invention is shown. In this embodiment, nozzle 500
includes an outer threaded surface 502 with retaining nut 504
threaded thereon to secure nozzle 500 against burner housing
portion 506, such as by engaging slot 507 and rotating nozzle 500
appropriately. Nozzle 500 includes a bored out portion, channel or
passageway 508 (shown in phantom) terminating in nozzle opening
509. Fuel enters fuel passageway 508 in a direction indicated by
arrow 512, and proceeds through passageway 508, where it is flows
out of the nozzle into an airflow via nozzle opening 509. Fuel is
injected at a fuel flow injection direction (F.sub.fuel) into a
prevailing air direction (F.sub.air). Again, the fuel is injected
through nozzle opening 509 such that at least a component of
F.sub.fuel is opposite to F.sub.air.
[0058] More localized mixing can occur at each counterflow
injection nozzle, and more specifically, via the holes through
which fuel is distributed or dispersed from each nozzle into the
prevailing air flow. In this fashion, the amount or level of
mixing, as well as the location(s) at which mixing takes place, can
be adjusted or varied to convenience by varying the size and
location of the holes.
[0059] It is contemplated that each of the above-described
embodiments of the inventive counterflow fuel injection nozzles can
include plurality of passageways, each having a unique
noninterfering fuel injection direction. By "noninterfering" it is
meant that, at the point at which fuel exits the nozzles (via the
nozzle openings), fuel from one passageway having a direction tends
not cross the direction of fuel passing from another passageway.
The holes can also be directed at various angles to achieve the
desired mixing qualities.
[0060] In another aspect of the present invention, a method of
mixing a fuel and air in a burner-boiler system is disclosed. The
system comprises a nozzle having a nozzle wall that defines a
nozzle interior for receiving the fuel, and the nozzle further
includes a fuel passageway formed in the nozzle wall. The method
comprises passing air in a prevailing airstream direction along an
exterior of the nozzle wall. The method further includes
distributing the fuel in a fuel flow injection direction from the
interior through the fuel passageway into the air passing in the
prevailing airstream direction along the exterior of the nozzle
wall. The method still further includes counterflow mixing the fuel
distributed in the fuel flow injection direction with the air
passing in the prevailing airstream direction. Significantly, at
least one vector component of the fuel flow injection direction
opposes at least one vector component of the prevailing airstream
direction.
[0061] Also, the use of the counterflow nozzle provides additional
burner stability with increased flue-gas recirculation (FGR) rates
(when FGR is used) to achieve lower NOx levels.
[0062] As is known to those skilled in the art, the turndown ratio
is the ratio of maximum fuel input rate to minimum fuel rate of a
variable input burner, and depends on burner size and control
methodology. Typical low NOx burners have limited turndown, but
with this invention, advantageously, with low NOx operation a
higher turndown ratio is possible, and a turndown of from about 7
to 1 to about 10 to 1 has been achieved using the present
counterflow injection nozzles.
[0063] It is noted that a gas mixing nozzle retrofit for a burner
used with a firetube boiler, commercial watertube or larger
industrial watertube boiler is contemplated. The retrofit may be
part of a kit that includes a counterflow fuel injection nozzle
that is used to replace a non-counterflow fuel injection nozzle. A
non-counterflow fuel injection nozzle would not provide for at
least one vector component of a fuel flow injection direction that
opposes at least one vector component of a prevailing air flow
direction when an airstream is provided in a prevailing air flow
direction in a location exterior of the nozzle.
[0064] According to another aspect of the present invention, a
counterflow fuel injection nozzle for injecting a gaseous fuel is
provided. The nozzle comprises a nozzle wall having an interior
surface that defines a nozzle interior and the interior receives a
fuel therein. The nozzle further includes a plurality of fuel
passageways formed in the nozzle wall for distributing the fuel
from the interior to a location exterior of the nozzle, and the
fuel is distributed to the exterior location in a fuel flow
injection direction. Then an airstream is provided in a prevailing
air flow direction in the location exterior of the nozzle, at least
one vector component of the fuel flow injection direction opposes
at least one vector component of the prevailing air flow direction.
In at least some embodiments (e.g., the "T-shaped" or
"hammerhead-type" embodiments), the counterflow fuel injection
nozzle can have at least one of the fuel passageways which
terminates in an opening having a diameter in a range of between
about 0.063 inches to about 0.189 inches. In at least some
embodiments (e.g., the "T-shaped" or "hammerhead-type"
embodiments), the counterflow fuel injection nozzle can have an
opening that has a diameter of about 0.1875 inches. In other
embodiments, the counterflow fuel injection nozzle of is used to
generate steam and/or hot water. In still other embodiments, the
counterflow fuel injection nozzle is used in a combustion
apparatus.
[0065] In accordance with yet another aspect of the present
invention, a combustion apparatus is disclosed. The combustion
apparatus includes a plurality of radially disposed lances, each of
the lances connected to at least one of the plurality of
counterflow fuel injection nozzles for injecting a gaseous fuel. In
at least some embodiments, each injection nozzle includes a nozzle
wall having an interior surface that defines a nozzle interior, and
the interior receives a fuel therein. In at least some embodiments,
each nozzle further includes a plurality of fuel passageways formed
in the nozzle wall for distributing the fuel from the interior to a
location exterior of the nozzle, and the fuel is distributed to the
exterior location in a fuel flow injection direction.
Advantageously, when an airstream is provided in a prevailing air
flow direction in the location exterior of the nozzle, at least one
vector component of the fuel flow injection direction opposes at
least one vector component of the prevailing air flow
direction.
[0066] Despite any methods being outlined in a step-by-step
sequence, the completion of acts or steps in a particular
chronological order is not mandatory. Further, modification,
rearrangement, combination, reordering, or the like, of acts or
steps is contemplated and considered within the scope of the
description and claims.
[0067] While the present invention has been described in terms of a
preferred embodiment(s), it is recognized that equivalents,
alternatives, and modifications, aside from those expressly stated,
are possible and within the scope of the appending claims.
* * * * *