U.S. patent application number 11/871701 was filed with the patent office on 2008-04-17 for swirl-stabilized burner for thermal management of exhaust system and associated method.
Invention is credited to Adam Coker, Wilbur H. Crawley, Thomas R. Hodnett, John Philip Nohl.
Application Number | 20080087013 11/871701 |
Document ID | / |
Family ID | 37570996 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080087013 |
Kind Code |
A1 |
Crawley; Wilbur H. ; et
al. |
April 17, 2008 |
Swirl-Stabilized Burner for Thermal Management of Exhaust System
and Associated Method
Abstract
An apparatus comprises a reciprocating or Wankel engine, an
exhaust gas passageway fluidly coupled to the engine, and a
fuel-fired burner. The burner is positioned in the exhaust gas
passageway and comprises a swirler configured to swirl exhaust gas
of the engine so as to stabilize in the exhaust gas passageway a
flame generated by the burner without use of supplemental
combustion air when the engine is operating above idle. An
associated method is disclosed.
Inventors: |
Crawley; Wilbur H.;
(Columbus, IN) ; Coker; Adam; (Whiteland, IN)
; Nohl; John Philip; (Indianapolis, IN) ; Hodnett;
Thomas R.; (Columbus, IN) |
Correspondence
Address: |
BARNES & THORNBURG LLP
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
US
|
Family ID: |
37570996 |
Appl. No.: |
11/871701 |
Filed: |
October 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11152869 |
Jun 15, 2005 |
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11871701 |
Oct 12, 2007 |
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10931009 |
Aug 31, 2004 |
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11871701 |
Oct 12, 2007 |
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60546139 |
Feb 20, 2004 |
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60536327 |
Jan 13, 2004 |
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Current U.S.
Class: |
60/320 ; 60/272;
60/324 |
Current CPC
Class: |
F01N 3/206 20130101;
F01N 3/2033 20130101; F01N 11/002 20130101; Y02T 10/47 20130101;
Y02T 10/26 20130101; F01N 3/0231 20130101; F01N 3/103 20130101;
F01N 3/025 20130101; F01N 13/009 20140601; F01N 3/035 20130101;
F01N 2240/36 20130101; F01N 2560/025 20130101; F01N 3/2892
20130101; F01N 2240/14 20130101; F01N 11/007 20130101; Y02T 10/40
20130101; Y02T 10/12 20130101; F01N 3/36 20130101; F01N 3/0256
20130101; F01N 3/0885 20130101; F01N 3/0814 20130101 |
Class at
Publication: |
060/320 ;
060/272; 060/324 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 1/00 20060101 F01N001/00 |
Claims
1. A method, comprising the steps of: generating a flame in exhaust
gas of a reciprocating or Wankel engine without use of supplemental
combustion air, swirling the exhaust gas while the engine is
operating above idle, and stabilizing the flame in the exhaust gas
as a result of the swirling step.
2. The method of claim 1, wherein: the swirling step comprises (i)
generating an outer swirl zone of swirling exhaust gas and (ii)
generating within the outer swirl zone an inner recirculation zone
of recirculating exhaust gas, and the stabilizing step comprises
stabilizing the flame in the inner recirculation zone.
3. The method of claim 1, wherein: the generating step comprises
generating a pilot flame, and the stabilizing step comprises
stabilizing the pilot flame as a result of the swirling step.
4. The method of claim 3, wherein: the generating step comprises
generating a main flame initiated by the pilot flame, and the
stabilizing step comprises stabilizing the main flame as a result
of the swirling step.
5. The method of claim 1, wherein: the generating step comprises a
generating a main flame initiated by a pilot flame, and the
stabilizing step comprises stabilizing the main flame as a result
of the swirling step.
6. The method of claim 1, wherein: the generating step comprises
generating a pilot flame in a perforated pilot tube, and the
swirling step comprises swirling exhaust gas with a swirler
surrounding the pilot tube so as to cause exhaust gas to enter the
pilot tube through apertures formed therein, further comprising the
step of forming a wall-cooling layer of exhaust gas on an inner
surface of the pilot tube with exhaust gas that has entered the
pilot tube through the apertures formed therein.
7. The method of claim 1, wherein the swirling step comprises
varying a swirl number of the exhaust gas.
8. The method of claim 1, wherein the swirling step comprises
swirling exhaust gas in opposite directions around an axis.
9. The method of claim 1, further comprising directing exhaust gas
toward a fuel dispenser by use of vanes adjacent to and inclined
toward one another and swirling the exhaust gas directed toward the
fuel dispenser about fuel dispensed from the fuel dispenser,
wherein the generating step comprises combusting the fuel dispensed
from the fuel dispenser to generate a main flame.
10. The method of claim 1, further comprising thermally managing an
emission abatement device by use of the swirl-stabilized flame.
11. An apparatus, comprising: a reciprocating or Wankel engine, an
exhaust gas passageway fluidly coupled to the engine, and a
fuel-fired burner positioned in the exhaust gas passageway and
comprising a first swirler configured to swirl exhaust gas of the
engine so as to stabilize in the exhaust gas passageway a flame
generated by the burner without use of supplemental combustion air
when the engine is operating above idle.
12. The apparatus of claim 11, wherein: the burner comprises a
pilot section configured to generate a pilot flame, and the pilot
section comprises a pilot fuel dispenser and the first swirler
which is positioned about the pilot fuel dispenser for stabilizing
the pilot flame.
13. The apparatus of claim 11, wherein: the burner comprises a
pilot section and a main section, the pilot section is configured
to generate a pilot flame and the main section is configured to
generate a main flame initiated by the pilot flame, and the main
section comprises the first swirler for stabilizing the main
flame.
14. The apparatus of claim 11, wherein: the burner comprises a
pilot section and a main section, the pilot section is configured
to generate a pilot flame and the main section is configured to
generate a main flame initiated by the pilot flame, the pilot
section comprises (i) a pilot fuel dispenser, (ii) the first
swirler which is positioned circumferentially about the pilot fuel
dispenser for stabilizing the pilot flame, (iii) a perforated pilot
tube that is configured to receive the pilot flame, and (iv) a
second swirler positioned circumferentially about the perforated
pilot tube for swirling exhaust gas to promote passage of exhaust
gas through apertures defined in the perforated pilot tube, and the
main section comprises (i) a main fuel dispenser for dispensing
fuel to be ignited at least initially by the pilot flame to
generate the main flame and (ii) a third swirler configured to
swirl exhaust gas so as to stabilize the main flame in the exhaust
gas passageway.
15. The apparatus of claim 14, further comprising a particulate
filter and an oxidation catalyst for heating the particulate
filter, wherein: there is a fuel-dosing section for introducing
fuel into the exhaust gas passageway upstream from the oxidation
catalyst to promote operation of the oxidation catalyst, the
fuel-dosing section is included as part of the burner or is
separate from the burner so as to be positioned downstream
therefrom at a location between the burner and the oxidation
catalyst, and the fuel-dosing section comprises a fuel-dosing
dispenser and a fourth swirler configured to swirl exhaust gas so
as to mix exhaust gas and fuel dispensed by the fuel-dosing
dispenser.
16. The apparatus of claim 11, wherein the first swirler comprises
at least one vane.
17. The apparatus of claim 16, further comprising a pitch adjuster
secured to the first swirler to adjust the pitch of the at least
one vane.
18. The apparatus of claim 16, wherein the at least one vane is
formed such that the pitch of the at least one vane varies along
the length of the at least one vane.
19. The apparatus of claim 11, further comprising an emission
abatement device, wherein the burner is positioned for thermal
management of the emission abatement device by use of the
swirl-stabilized flame.
20. A method, comprising the steps of: generating both a pilot
flame and a main flame in exhaust gas of a reciprocating or Wankel
engine without use of supplemental combustion air, swirling the
exhaust gas about an axis while the engine is operating above idle,
and stabilizing both the pilot flame and the main flame in the
exhaust gas as a result of the swirling step.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/152,869, filed Jun. 15, 2005, and is a continuation in part
of U.S. application Ser. No. 10/931,009, filed Aug. 31, 2004, which
claimed the benefit of U.S. Provisional Patent Application Ser. No.
60/546,139 filed on Feb. 20, 2004 and U.S. Provisional Patent
Application Ser. No. 60/536,327 filed on Jan. 13, 2004, the
entirety of all above applications is hereby incorporated by
reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to apparatus and
methods for thermally managing emission abatement devices.
BACKGROUND OF THE DISCLOSURE
[0003] There are a variety of ways to heat emission abatement
devices. For example, fuel-fired burners and electric heaters have
been used in connection with some types of emission abatement
devices.
SUMMARY OF THE DISCLOSURE
[0004] According to an aspect of the present disclosure, there is
provided an apparatus comprising a fuel-fired burner that is
positioned in an exhaust gas passageway and comprises a swirler
configured to swirl exhaust gas of a reciprocating or Wankel engine
so as to stabilize in the exhaust gas passageway a flame generated
by the burner without use of supplemental combustion air when the
engine is operating at idle and above idle. The swirl-stabilized
flame is useful for thermally managing an emission abatement
device. An associated method is disclosed.
[0005] Such flame stabilization has a number of benefits. For
example, it promotes use of the burner during occurrences of
relatively high exhaust gas flow rates which might otherwise blow
out the flame. In addition, the diameter of the burner can be
reduced since the burner can handle such relatively high flow
rates. Further, flame stabilization promotes reduction of the flame
length, thereby allowing the burner length to be reduced
accordingly. A relatively compact burner package can thus be
provided for applications where space economy may be a factor
(e.g., onboard a vehicle).
[0006] The burner may have a plurality of swirlers for swirling
exhaust gas to promote flame stabilization. In an exemplary
implementation, the burner has three swirlers, two in a pilot
section of the burner and one in a main section of the burner. One
of the swirlers of the pilot section is positioned about a pilot
fuel nozzle for stabilizing a pilot flame generated by the pilot
section. The other pilot section swirler is positioned about a
perforated pilot tube to promote passage of oxygen present in
exhaust gas through apertures defined in the pilot tube into the
pilot flame. The swirler in the main section is used to stabilize a
main flame initiated by the pilot flame.
[0007] Swirl stabilization of the pilot flame and/or the main flame
is useful for thermally managing a variety of emission abatement
devices. Such emission abatement devices include, but are not
limited to, oxidation catalysts (e.g., diesel oxidation catalysts),
particulate filters (e.g., catalyzed or uncatalyzed diesel
particulate filters), selective catalytic reduction devices ("SCR
devices"), and/or NOx traps.
[0008] The above and other features of the present disclosure will
become apparent from the following description and the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a simplified block diagram showing an apparatus
for thermally managing an emission abatement device by use of a
swirl-stabilized flame of a burner;
[0010] FIG. 2 is a fragmentary perspective view of the burner;
[0011] FIG. 3 is a sectional view taken along lines 3-3 of FIG.
2;
[0012] FIG. 3a is a sectional view of a portion of a pilot tube
showing a wall-cooling layer of exhaust gas formed on an inner
surface of the pilot tube;
[0013] FIG. 4 is a sectional view taken along lines 4-4 of FIG.
3;
[0014] FIG. 5 is a perspective view of an upstream side of a
variable swirler;
[0015] FIG. 6 is an elevation view of the upstream side of the
variable swirler;
[0016] FIG. 7 is a perspective view of a downstream side of the
variable swirler;
[0017] FIG. 8 is a perspective view of a twisted vane of a
swirler;
[0018] FIG. 9 is a sectional view taken along lines 9-9 of FIG. 3
showing an alternative embodiment of components of the burner;
[0019] FIG. 10 is a perspective view of an embodiment of a
swirler;
[0020] FIG. 11 is a rear elevation view of the swirler of FIG.
10;
[0021] FIG. 12 is an end elevation view of the swirler of FIGS. 10
and 11; and
[0022] FIG. 13 is a perspective view showing a swirler tube
positioned about a fuel dispenser.
DETAILED DESCRIPTION OF THE DRAWINGS
[0023] While the concepts of the present disclosure are susceptible
to various modifications and alternative forms, specific exemplary
embodiments thereof have been shown by way of example in the
drawings and will herein be described in detail. It should be
understood, however, that there is no intent to limit the
disclosure to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and
alternatives following within the spirit and scope of the invention
as defined by the appended claims.
[0024] Referring to FIG. 1, there is shown an apparatus 10
comprising a burner 12 that generates a swirl-stabilized flame 14
in exhaust gas ("EG" in the drawings). The exhaust gas is from a
reciprocating (e.g., piston) or Wankel (e.g., rotary) internal
combustion engine 16 (e.g., diesel engine) for use in thermal
management of an emission abatement device 18. The burner 12
generates the flame 14 without use of supplemental combustion air.
In other words, it uses the oxygen present in the exhaust gas for
the combustion reaction. The burner 12 is positioned in an exhaust
gas passageway 20 and comprises a swirler 22 configured to swirl
exhaust gas so as to stabilize in the exhaust gas passageway 18 the
flame 14 generated by the burner 12. The burner 12 is thus able to
stabilize the flame 14 when the engine 16 is at idle and above
idle.
[0025] Illustratively, the swirler 22 swirls exhaust gas to
generate an outer swirl zone 24 of swirling exhaust gas which
induces generation of an inner recirculation zone 26 of
recirculating exhaust gas within the swirl zone 24. In the swirl
zone 24, exhaust gas swirls around an axis 28 of the burner 12
(e.g., in a clockwise direction or counter-clockwise direction) as
the exhaust gas advances downstream along the axis 28. In the
recirculation zone 26, exhaust gas recirculates back toward the
swirler 22. The swirl zone 24 may have a relatively high velocity
depending, for example, on the output of the engine 16. However,
the recirculation zone 26 has a relatively low velocity conducive
to flame stabilization. In other words, the velocities in the
recirculation zone 26 are sufficiently low to allow the flame 14 to
reside therein without being blown out by the potentially higher
velocities in the outer swirling zone 24. The flame 14 is thus
stabilized in and near the recirculation zone 26 by use of the
swirler 22.
[0026] The swirler 22 may be configured to generate one or more
secondary recirculation zones 29 as well. Illustratively, the
swirler 22 provides a sudden change in the flow area (i.e., a "dump
plane") at its periphery. Such a feature generates secondary
recirculation zones 29 just downstream therefrom. The zones 29 may
thus be used to promote flame stabilization in the zones 29 in
addition to or in place of the recirculation zone 26.
[0027] It is within the scope of this disclosure to configure the
swirler 22 so as to swirl the exhaust gas to achieve any swirl
number, the swirl number being indicative of the amount of swirl
induced in the flow per unit length. For example, swirl numbers
between about 0.5 and about 2.0 may be particularly useful to
promote stabilization of the flame 14. Swirl numbers between about
0.76 and 1.1 may be most useful to promote stabilization of flame
14.
[0028] Swirl stabilization of the flame 14 has a number of
benefits. For example, it promotes use of the burner 12 during
occurrences of relatively high exhaust gas flow rates which might
otherwise blow out the flame 14. This may be particularly useful
with vehicles such as relatively large commercial vehicles (e.g.,
truck tractors, buses) that have a relatively large engine (e.g.,
12.7 liter engine) capable of producing a relatively large amount
of exhaust gas. In addition, flame stabilization promotes provision
of a relatively compact burner package for applications where space
economy may be a factor. In particular, the diameter of the burner
12 can be reduced since the burner 12 can handle relatively high
exhaust gas flow rates. Further, the burner length can be reduced
since flame stabilization results in a shorter flame length. The
burner 12 with its swirler 22 is thus particularly useful in an
exhaust system.
[0029] The emission abatement device 18 is thermally managed by use
of the swirl-stabilized flame 14. In particular, exhaust gas
passing through the burner 12 is heated thereby and advances to the
emission abatement device 18 to heat the emission abatement device
18.
[0030] The device 18 may take a variety of forms. Exemplarily, the
device 18 may include an oxidation catalyst (e.g., diesel oxidation
catalyst), a particulate filter (e.g., catalyzed or uncatalyzed
diesel particulate filter), an SCR device, and/or a NOx trap.
[0031] According to one example, the device 18 includes an
oxidation catalyst and a particulate filter. In such a case, the
oxidation catalyst is positioned fluidly between the burner 12 and
the particulate filter. The exhaust gas heated by the
swirl-stabilized flame 14 heats the oxidation catalyst to its
operational temperature (e.g., between about 250.degree. C. and
about 300.degree. C.). The oxidation catalyst then oxidizes fuel
that has been introduced into the exhaust gas at the burner 12 or
at a location separate and from the burner 12. Heat generated by
the exothermic reaction at the oxidation catalyst heats the
particulate filter to burn off particulate matter trapped thereby
so as to regenerate the particulate filter for further use. It is
within the scope of this disclosure to use the swirl-stabilized
flame to regenerate the particulate filter without the assistance
of an oxidation catalyst.
[0032] In the case where the device 18 is an SCR device, the
swirl-stabilized flame 14 is used to facilitate establishment of
the SCR device within its operational temperature range. In the
case of a NOx trap, the swirl-stabilized flame 14 may be used to
elevate the temperature of the NOx trap to facilitate
de-sulfurization of the NOx trap. Further, the burner 12 may be
used with the exhaust systems of U.S. Pat. No. 6,871,489, the
disclosure of which is hereby incorporated by reference herein.
[0033] Referring to FIGS. 2 and 3, there is shown an exemplary
implementation of the burner 12. In particular, there is shown a
fuel-fired burner 112 for use as the burner 12 in the apparatus 10
to thermally manage the emission abatement device 18 in any of its
forms. The burner 112 comprises a number of swirlers positioned in
an exhaust gas passageway 120 defined in part by a housing 118 of
the burner 112 to swirl exhaust gas flowing from the engine 16 to
the emission abatement device 18 for flame stabilization in the
passageway 120 even during occurrences of relatively high exhaust
gas flow rates.
[0034] The burner 112 comprises a pilot section 130 and a main
section 132. The pilot section 130 generates a swirl-stabilized
pilot flame 134 used to initiate a swirl-stabilized main flame 136
of the main section 132. Once the main flame 136 is initiated, the
pilot section 130 can be shut down to extinguish the pilot flame
134 or can be continued to be operated.
[0035] The pilot section 130 comprises a swirl-stabilized pilot
fuel dispenser 138 (see also FIG. 4). The dispenser 138 extends
through an aperture formed in a first swirler 122a such that the
swirler 122a circumferentially surrounds the dispenser 138. The
swirler 122a is secured to an end of a perforated pilot tube 142
and is configured as a plate comprising a plurality of radially
extending vanes 144 that are inclined to swirl exhaust gas in the
pilot tube 142 either clockwise or counter-clockwise (depending on
the orientation of the vanes 144) about a burner axis 145. As such,
the swirler 122a generates an outer swirl zone 24 of swirling
exhaust gas in the pilot tube 142 and an inner recirculation zone
26 of recirculating exhaust gas within the outer swirl zone 24.
[0036] The dispenser 138 dispenses fuel supplied by a pilot fuel
line 148 into the recirculation zone 26 for ignition of the fuel by
an igniter 146 that extends into the recirculation zone 26. In this
way, the pilot flame 134 is initiated in the pilot tube 142.
Moreover, the pilot flame 134 is stabilized in the pilot tube
recirculation zone 26 due to the relatively low exhaust gas
velocities in that zone 26. A flow-obstructing device 150 which may
be used to hold the pilot flame 134 is mounted in the pilot tube
142 to further facilitate stabilization of the pilot flame 134.
[0037] A second swirler 122b of the pilot section 130 mates against
the housing 118 and is secured thereto so as to be mounted in the
passageway 120. The pilot tube 142 extends through an aperture
defined in the swirler 122b such that the swirler 122b surrounds
the pilot tube 142 and the pilot tube 142 is secured to the swirler
122b. The pilot tube 142, the swirler 122a, and the dispenser 138
secured to the pilot tube 142 are thus mounted in the passageway
120.
[0038] The swirler 122b is configured, for example, as a plate
comprising inclined radially extending vanes 153 that swirl exhaust
gas outside the pilot tube 142 in either a clockwise or
counter-clockwise direction (depending on the orientation of the
vanes 153) about the burner axis 145. In this way, the swirler 122b
causes exhaust gas to pass through apertures 154 defined in the
pilot tube 142 so as to "feed" oxygen present in the exhaust gas to
the pilot flame 134 for combustion with the pilot fuel. In
addition, exhaust gas which passes through the apertures 154 into
the pilot tube 142 due to the swirler 122b forms a generally
annular wall-cooling layer 155 of exhaust on the inner surface of
the pilot tube 142. This wall-cooling layer 155 serves as a layer
of thermal insulation between the pilot tube 142 and the pilot
flame 134, thereby enhancing the durability of the pilot tube 142
and permitting use of less costly materials for the pilot tube 142.
The thickness of the wall-cooling layer 155 may be about 1/8
inch.
[0039] The main section 132 is positioned just downstream from the
pilot section 130. A main fuel dispenser 156 secured to the housing
118 receives fuel from a main fuel line 122c and dispenses that
fuel into the main section 132 for generation of the main flame
136.
[0040] The main section 132 comprises a third swirler 122c for
swirl-stabilization of the main flame 136. The swirler 122c is
configured, for example, as a plate comprising inclined radially
extending vanes 159 that swirl exhaust gas in either a clockwise or
counter-clockwise direction (depending on the orientation of the
vanes 159) about the burner axis 145 upon passage of the exhaust
gas through the swirler 122c. This generates immediately downstream
from the swirler 122c an outer swirl zone 24 of swirling exhaust
gas in the housing 118 of the main section 132. This outer swirl
zone 24 of the main section 132 induces an inner recirculation zone
26 of recirculating exhaust gas within the main section outer swirl
zone 24. The main flame 136 is stabilized in this main section
recirculation zone 26 due to the relatively low exhaust gas
velocities present in this zone 26. A transition member 160 secured
to an upstream side of the swirler 122c facilitates passage of
exhaust gas through the swirler 122c.
[0041] The swirler 122c comprises a dump plane 162 along an outer
periphery of the swirler 122c. The dump plane 162 is an imperforate
annular wall that blocks flow of exhaust gas therethrough so as to
generate a radially outer recirculation zone immediately downstream
from the dump plane 162 for flame stabilization in that zone also.
It is within the scope of this disclosure to omit the dump plane
162 and extend the vanes 159 to the outer periphery of the swirler
122c.
[0042] The burner 112 may include a fuel-dosing section 164 for
dispensing fuel into the heated exhaust gas for use with a
downstream oxidation catalyst or other component of the emission
abatement device 18. In such a case, the fuel-dosing section 164
has a fuel-dosing dispenser 166 secured to the housing 118. The
dispenser 166 dispenses dosing fuel supplied by a dosing fuel line
168 into the passageway 120 at a location between the swirler 122c
and a fourth swirler 122d. The swirler 122d is configured, for
example, as a plate comprising inclined vanes 172 that swirl the
dosing fuel and exhaust gas in either a clockwise or
counter-clockwise direction (depending on the orientation of the
vanes 172) about the burner axis 145 upon passage through the
swirler 122d. In this way, the dosing fuel is thoroughly mixed with
the exhaust gas upon arrival at the emission abatement device 18.
It is within the scope of this disclosure to omit the fuel-dosing
section 164 altogether from the apparatus 10 or to include the
fuel-dosing section 164 as a component separate from the burner 112
such that the fuel-dosing section is positioned downstream from the
burner 112 at some location between the burner 112 and the emission
abatement device 18.
[0043] It is within the scope of this disclosure to configure the
swirlers 122a, 122b, 122c, 122d so as to swirl the exhaust gas to
achieve any swirl number. For example, swirl numbers between about
0.5 and about 2.0 may be particularly useful to promote flame
stabilization of flames 134 and 136. Swirl numbers between about
0.76 and 1.1 may be most useful to promote such flame
stabilization.
[0044] Referring to FIG. 3, there is a shown a control system 174
for controlling operation of the burner 112. In particular, the
control system 174 is responsive to inputs from an upstream oxygen
sensor 176, an upstream temperature sensor 178, and a downstream
temperature sensor 180 to control operation of a fuel and ignition
module 182 which controls supply of fuel to fuel lines 148, 122c,
168 and supply of electricity via an ignition cable 184 to the
igniter 146.
[0045] The direction of inclination of the vanes 144, 153, 159, 172
of the swirlers 122a, 122b, 122c, 122d may take a variety of forms.
For example, all the vanes of the swirlers 122a, 122b, 122c, 122d
may be inclined to swirl exhaust gas in the same direction about
the axis 145. In other examples, the vanes 144, 153, 159, 172 of
one or more swirlers 122a, 122b, 122c, 122d may be inclined to
swirl exhaust gas in clockwise direction whereas the vanes 144,
153, 159, 172 of the other swirler(s) 122a, 122b, 122c, 122d may be
inclined to swirl exhaust gas in a counter-clockwise direction.
[0046] The vanes 144, 153, 159, 172 of any swirler 122a, 122b,
122c, 122d may have different pitches (the "pitch" is the angle of
inclination of a vane). For example, some of vanes of a given
swirler may have one or more pitches to swirl exhaust gas in a
clockwise direction and some of the vanes of that same swirler may
have one or more pitch angles to swirl exhaust gas in a
counter-clockwise direction. Use of such pitch angles promotes
mixing of exhaust gas. An example of such a swirler is shown in
FIG. 15 and discussed below in connection therewith.
[0047] The vanes 144, 153, 159, 172 of any swirler 122a, 122b,
122c, 122d may be fixed against movement relative to the housing
118 or may be movable relative to the housing 118. As such, the
pitch of the vanes may be invariable or variable.
[0048] Referring to FIGS. 5-7, there is shown a variable swirler
222 for use as any one or more of the swirlers 22, 122a, 122b,
122c, 122d. The swirler 222 has a plurality of variable-pitch,
radially extending vanes 230. The pitch of the vanes 230 can be
varied by a pitch adjuster 232 operable by the control system 174.
In this way, the swirl number associated with the flow of exhaust
gas can be varied. For example, the vanes 230 can be adjusted so as
not to be inclined when the burner is shut down in order to reduce
back pressure on the engine 16 associated with vane inclination. In
other examples, the pitch of the vanes 230 can be adjusted in
response to conditions associated with the exhaust gas (e.g., flow
rate, temperature, pressure, and/or oxygen content) to control
flame stabilization. The swirl number associated with the exhaust
gas can thus be varied accordingly.
[0049] The vanes 230 are mounted within a stationary frame for
pivotable movement relative thereto. Exemplarily, the vanes 230 are
secured to a stationary outer mounting ring 234 surrounding the
vanes 230 and a stationary inner mounting hub 236. The hub 236 is
mounted within the mounting ring 234 by a plurality of stationary
mounting rods 238 (e.g., five). A transition member 260 is secured
to the upstream side of the hub 236 to facilitate passage of flow
through the swirler 222.
[0050] The pitch adjuster 232 comprises a drive unit 240 and a
connector 242 operable by the drive unit 240 to pivot the vanes 230
to adjust their pitch. The drive unit 240 may have a motor (e.g.,
electric motor) and associated reduction gearing for rotating a
rotatable drive shaft 244. The connector 242 comprises a lever 246
secured to the shaft 244 to be pivoted thereby upon rotation of the
shaft 244. Such pivoting movement of the lever 246 moves a link 248
back and forth to cause a rotatable ring 250 to rotate about a
swirler axis 252 of the swirler 222. Rotation of the ring 250
causes a pivot 254 associated with each vane 230 and extending
through the mounting ring 234 thereto to pivot about a vane axis
256 of the vane 230. Such pivotable movement of the pivots 254
causes each vane 230 to rotate about its vane axis 256 to adjust
the pitch thereof. In this way, a desired swirl number associated
with the exhaust gas can be achieved in order to promote flame
stabilization of either or both of the pilot flame 134 and the main
flame 136 in the case of a non-zero swirl number and to promote
reduction of engine back pressure in the case of a zero or
near-zero swirl number.
[0051] Further, in the case of a burner having multiple swirlers as
with the burner 112, such pitch adjustment can be used to swirl the
flow in opposite directions. In particular, the vanes of one or
more swirlers may be configured by the adjuster 232 to swirl
exhaust gas in one direction whereas the vanes of one or more other
swirlers may be configured by the adjuster 232 to swirl exhaust gas
in an opposite direction.
[0052] It is within the scope of this disclosure to achieve any
swirl number by use of the swirler 220 and pitch adjuster 232. For
example, swirl numbers between about 0.5 and about 2.0 may be
particularly useful to promote flame stabilization. Swirl numbers
between about 0.76 and 1.1 may be most useful to promote flame
stabilization.
[0053] Referring to FIG. 8, there is shown a vane 320 for use with
any of the swirlers 22, 122a, 122b, 122c, 122d, 222. The vane 320
has a pitch that varies along the length of the vane 320 between a
radially inner root 321 of the vane 320 and a radially outer tip
323 of the vane 320. Exemplarily, the vane 320 twists about a
longitudinal axis 356 of the vane 320. The pitch of the vane 320 is
thus varied along the length of the vane 320 to balance the
pressure drop across the vane 320, to tailor flame stabilization,
and to enhance the capacity of the vane 320 to address thermal
fatigue by balancing vane loading. Further, the flow across the
vane 320 is about the same at the center of the vane 320 as at the
tip 323, producing a relatively uniform flow across the swirler to
enhance mixing and thermal distribution when each of the vanes of
the swirler is configured like the vane 320.
[0054] Referring to FIG. 9, there shown a swirler 422b used in
place of the swirler 122b. The swirler is configured to swirl
portions of the exhaust gas and to direct other portions of the
exhaust gas toward a pair of fuel dispensers 156.
[0055] Referring to FIGS. 10-12, there is shown the swirler 422b.
Swirl vanes 423 of the swirler 422b are inclined at a pitch 424 of,
for example, about 45.degree. to swirl exhaust gas that passes
swirl vanes 423.
[0056] Guide vanes 425 of the swirler 422b are used to direct
exhaust gas that passes the guide vanes 425 toward the fuel
dispensers 156. There are two pairs of guide vanes 425, each pair
being associated with one of the fuel dispensers 156. The guide
vanes 425 of each pair are inclined toward one another at a pitch
427 of, for example, about 60.degree. in order to direct exhaust
gas axially toward the associated fuel dispenser 156.
[0057] Referring to FIG. 13, there is shown a swirler tube 451
surrounding a nozzle 452 of a fuel dispenser 156. Exhaust gas is
directed by a pair of guide vanes 425 toward the fuel dispenser
156. Such exhaust gas flows through apertures 454 defined in an
upstream side of the swirler tube 451. Vanes 456 of the upstream
side of the tube 451 impart a swirl to the exhaust gas that flows
through the apertures 454 so that the exhaust gas flows around a
dispenser axis 458 of the fuel dispenser 156 and around fuel spray
460 discharged from the nozzle 452 as shown by an arrow 462. In
this way, the fuel spray 460 is shielded from incoming exhaust gas,
promoting advancement of the fuel spray 460 into the main flame 136
and promoting fuel vaporization. Impingement of the fuel spray 460
on the swirler 122c and the pilot tube 142 is also reduced.
Further, the swirling exhaust gas in the tube 451 swirl-stabilizes
the nozzle 452.
[0058] A flow-obstructing device 450 is secured to and extends from
a distal end of the tube 451. Exemplarily, the device 450 is shaped
generally as half of a spoon. The device 450 serves, for example,
as a flame holder for the pilot flame 134 and/or the main flame 136
to further assist in flame stabilization.
[0059] Each of the swirlers 22, 122a, 122b, 122c, 222, 422b or
combinations thereof provides means for swirling exhaust gas so as
to stabilize in the exhaust gas passageway 20 or 120 a flame 14,
134, and/or 136 generated by the burner 12 or 112 for thermal
management of the emission abatement device 18.
[0060] While the concepts of the present disclosure have been
illustrated and described in detail in the drawings and foregoing
description, such illustration and description is to be considered
as exemplary and not restrictive in character, it being understood
that only illustrative embodiments have been shown and described
and that all changes and modifications that come within the spirit
of the disclosure are desired to be protected.
[0061] There are a plurality of advantages of the concepts of the
present disclosure arising from the various features of the systems
described herein. It will be noted that alternative embodiments of
each of the systems of the present disclosure may not include all
of the features described yet still benefit from at least some of
the advantages of such features. Those of ordinary skill in the art
may readily devise their own implementations of a system that
incorporate one or more of the features of the present disclosure
and fall within the spirit and scope of the invention as defined by
the appended claims.
* * * * *