U.S. patent number 3,742,702 [Application Number 05/108,893] was granted by the patent office on 1973-07-03 for regenerative gas turbine system.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to Ronald E. Quinn.
United States Patent |
3,742,702 |
Quinn |
July 3, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
REGENERATIVE GAS TURBINE SYSTEM
Abstract
A regenerative gas turbine engine with combustion apparatus
including a conventional combustion liner has the compressor
connected to the combustion apparatus so as to supply primarily air
unheated by the regenerator to the combustion zone of the liner and
primarily air heated by the regenerator to the dilution zone of the
liner, to reduce generation of oxides of nitrogen. An adjustable
valve provides for varying the ratio of unheated to heated air.
Inventors: |
Quinn; Ronald E. (Indianapolis,
IN) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
22324666 |
Appl.
No.: |
05/108,893 |
Filed: |
January 22, 1971 |
Current U.S.
Class: |
60/39.23;
60/39.511; 60/760 |
Current CPC
Class: |
F02C
7/08 (20130101); F23R 3/04 (20130101) |
Current International
Class: |
F23R
3/04 (20060101); F02C 7/08 (20060101); F02c
007/10 () |
Field of
Search: |
;60/39.23,39.65,39.51 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
604,114 |
|
Jun 1948 |
|
GB |
|
532,314 |
|
Oct 1956 |
|
CA |
|
212,269 |
|
Feb 1941 |
|
CH |
|
Primary Examiner: Goodridge; Laurence M.
Assistant Examiner: Flint; Cort R.
Claims
I claim:
1. A regenerative gas turbine engine comprising, in combination,
air compressor means, a combustion apparatus supplied from the
compressor means, the combustion apparatus including a combustion
products generator having a combustion zone and a dilution zone,
turbine means energized from the combustion apparatus connected to
drive the compressor means, a heat exchanger, and a turbine exhaust
duct connected through one pass of the heat exchanger; the heat
exchanger having a second pass in heat exchange relation to the
first pass; a first compressed air conduit leading from the
compressor means to the combustion zone by-passing the heat
exchanger; a second compressed air conduit leading from the
compressor means through the second pass of the heat exchanger to
the dilution zone, and flow splitter valve means between the
compressor and the said conduits reversely throttling the flow into
the conduits for dividing the compressor output between the said
conduits variably as a function of engine power level so as to
direct air unheated by the regenerator primarily to the combustion
zone and air heated by the regenerator primarily to the dilution
zone so as to minimize the temperature of the air entering the
combustion zone to reduce combustion temperature and thereby
generation of oxides of nitrogen.
2. A regenerative gas turbine engine comprising, in combination,
air compressor means, a combustion apparatus supplied from the
compressor means, the combustion apparatus including a combustion
products generator having a combustion zone and a dilution zone,
turbine means energized from the combustion apparatus connected to
drive the compressor means, a heat exchanger, and a turbine exhaust
duct connected through one pass of the heat exchanger; the heat
exchanger having a second pass in heat exchange relation to the
first pass; a first compressed air conduit leading from the
compressor means to the combustion zone by-passing the heat
exchanger; a second compressed air conduit leading from the
compressor means through the second pass of the heat exchanger to
the dilution zone, means for dividing the compressor output between
the said conduits so as to direct air unheated by the regenerator
primarily to the combustion zone and air heated by the regenerator
primarily to the dilution zone; and flow splitter valve means
between the compressor and the said conduits reversely throttling
the flow into the conduits for varying the division of air between
the said conduits in accordance with a condition of engine
operation so as to minimize the temperature of the air entering the
combustion zone to reduce combustion temperature and thereby
generation of oxides of nitrogen.
3. A regenerative gas turbine engine comprising, in combination, in
flow sequence as recited, air compressor means, a first compressed
air conduit leading from the compressor means to the combustion
zone of a combustion apparatus, the combustion zone of the
combustion apparatus, the dilution zone of the combustion
apparatus, turbine means including means driving the compressor
means, and a turbine exhaust duct including one pass of a heat
exchanger; the heat exchanger having a second pass in heat exchange
relation to the first pass; a second compressed air conduit leading
from the compressor means through the second pass of the heat
exchanger to the dilution zone of the combustion apparatus, flow
splitter valve means between the compressor and the said conduits
reversely throttling the flow into the conduits for variably
dividing compressor output between the said conduits so as to
direct air unheated by the regenerator primarily to the combustion
zone and air heated by the regenerator primarily to the dilution
zone, and means for variably setting the flow splitter valve means
as a function of fuel-air ratio in the combustion apparatus so as
to minimize the temperature of the air entering the combustion zone
to reduce combustion temperature and thereby generation of oxides
of nitrogen.
Description
My invention is directed to regenerative gas turbine engines, and
particularly to improving the cleanness of combustion of such
engines.
Since gas turbines are continuous combustion engines and ordinarily
supply a considerable excess of air over stoichiometric to the
combustion apparatus, they are naturally capable of cleaner
combustion; that is, of an exhaust having less of constituents
which may be considered pollutants, than engines of intermittent
combustion types, particularly intermittent combustion engines
operating at or near stoichiometric fuel to air ratios.
However, the combustion apparatuses of gas turbine engines
ordinarily operate by burning the fuel in which is termed the
combustion zone of the combustion apparatus, in which the fuel is
atomized and burned in a minor portion of the air. Downstream in
the flow through the combustion apparatus, in what is called the
dilution zone, additional air is introduced and mixed with the
combustion products to cool them and produce the turbine motive
fluid. It has not appeared feasible, for various reasons which need
not be gone into here, to distribute the fuel through the entire
body of air flowing through the engine and thus achieve combustion
at a low fuel to air ratio.
Experience has shown that the continuous flow gas turbine
combustion apparatus provides an engine exhaust almost entirely
free of carbon monoxide and unburned fuel or fuel constituents.
However, the high temperature of combustion causes some formation
of nitrogen oxides by combination of the nitrogen and oxygen
present in the air supplied to the engine. The higher the
temperature in the combustion zone, the greater the tendency for
formation of nitrogen oxides.
This problem is accentuated when the engine includes a regenerator
or recuperator or, in other words, a heat exchanger by which heat
is transferred from the engine exhaust to the air flowing from the
engine compressor to the combustion apparatus. The heat exchanger,
which will be referred to hereafter as a regenerator, is a
practical necessity in some applications as a means to improve the
fuel economy of the engine. However, since the regenerator raises
the temperature of the air entering the combustion apparatus, the
problem of nitrogen oxide formation is aggravated.
My invention is based upon the concept that the air flowing to the
combustion apparatus should be divided and most or all of the air
for direct combustion; that is, the primary combustion air, should
by-pass the regenerator so as to remain relatively cool; and that
the remainder of the air flowing through the engine be passed
through the heat exchanger and then be supplied to the combustion
apparatus for dilution purposes. While this can be shown to result
in some lowering of thermal efficiency or fuel economy of the
engine, it is a way to lower percentages of nitrogen oxide because
of the lower maximum temperature in the combustion zone. The fuel
consumption is much the same, and the cooler combustion air does
not rise to so high a temperature in the flame.
However, since the ratio of fuel to air varies with the power
output of the engine, a smaller proportion of the air is needed for
the primary combustion zone at light loads. Therefore, I provide
valve means to vary the ratio of air by-passing the regenerator to
that flowing through it, so as to maintain the maximum efficiency
of regeneration consonant with minimization of nitrogen oxide
generation as load varies.
The general nature of my invention should be apparent from the
foregoing, but it will be made more clear to those skilled in the
art from the succeeding detailed description and accompanying
drawings of the preferred embodiment of the invention.
Th principal objects of my invention are to minimize undesirable
constituents in the exhaust of a gas turbine engine, to lower the
maximum temperature in the combustion zone of a regenerative gas
turbine combustion apparatus, to improve the cleanness of the
exhaust of a gas turbine engine without undue sacrifice of
operating efficiency of theengine, and to provide a simple and
effective arrangement for dividing the air flow from the compressor
of a gas turbine engine between a first path into the primary
combustion zone and a second path through a regenerative heat
exchanger into the dilution zone of the combustion apparatus of the
engine.
Referring to the drawings:
FIG. 1 is a schematic diagram of a regenerative gas turbine engine
incorporating the invention.
FIG. 2 is a sectional view of an air flow controlling valve taken
on the plane indicated by the line 2--2 in FIG. 3.
FIG. 3 is a sectional view of the valve taken on the plane
indicated by the line 3--3 in FIG. 2.
FIG. 1, except for the improvement which forms the subject matter
of my invention, illustrates a typical regenerative gas turbine
engine of the free turbine type. The engine includes an air
compressor 2 which discharges through a compressed air conduit 3 to
a valve 4 which controls the division of flow between a first
compressed air conduit 6, leading to combustion apparatus 7, and a
second compressed air conduit 8. The combustion apparatus 7
includes an outer case 10 and a combustion liner or flame tube 11,
the combustion liner being enclosed within the outer case for flow
of air from within the case into the liner. The combustion liner
includes an outlet or transition portion 12 from which combustion
products are discharged from the combustion apparatus through a
conduit 14 into a first or high pressure turbine 15. Turbine 15
drives the compressor 2 through a shaft 16.
The exhaust from turbine 15 is supplied to a second or low pressure
turbine 18. While ordinarily these two turbines are integrated
structurally, they are illustrated here as being connected through
a combustion products conduit 19. The turbine 18 drives a shaft 20
which may be connected to drive any load including, for example,
the driving wheels of a self-propelled vehicle. The two turbines
may be mechanically coupled together, or a single turbine driving
shafts 16 and 20 may be used. The low pressure exhaust from turbine
18 is conducted through suitable ducting 22 to a heat exchanger 23
where the exhaust gas flows through one pass 24 of the heat
exchanger to an atmospheric exhaust 26. The heat exhanger may be of
any suitable type such, for example, as a rotary regenerator or a
fixed recuperator. As employed in a conventional gas turbine
engine, its purpose is to recover heat from the hot low pressure
exhaust gases and heat the compressed air flowing from the
compressor to the combustion apparatus so as to reduce the fuel
consumption required to provide the high temperature motive
fluid.
The second compressed air conduit 8 previously referred to leads to
a compressed air pass 27 of the heat exchanger 23 from which the
heated compressed air flows through a conduit 28 to the combustion
apparatus 7.
Fuel from a suitable source of fuel under pressure is led through a
fuel line 30, a fuel control represented as a fuel controlling
valve 31, and a line 32 to a fuel spray nozzle 34 at the upstream
end of the combustion liner 11. The valve 31 may be taken as a
symbolic representation of suitable fuel controlling means for the
engine which may, of course, include such usual components as
maximum and minimum flow limiters and governing devices but which,
in any usual case, includes a trhottling valve which ultimately
controls the rate of flow of fuel to the combustion apparatus. The
fuel controller 31 is represented as being set to the desired power
level by a control input 35 which may be a hand lever or an
accelerator pedal of a vehicle.
The combustion apparatus 7, except as specifically pointed out
below, is of a well known type in which the case 10 contains the
comreessed air which is diffused and flows at relatively low
velocity within the case, flowing through openings in the liner 11
to the interior of the liner. Fuel is sprayed into the air within
the liner by the nozzle 34, is burned, and the resulting combustion
products are discharged through the outlet portion 12 of the
combustion apparatus. The liner 11 is preferably made up of a
number of sections; a dome 36, and successive rings such as 38, 39,
and 40. The foward part of the liner, which might correspond
approximately to the portion enclosed by the dome 36, the first
ring 38, and some or all of the second ring 39, may be considered
the primary combustion zone of the liner within which fuel is
burned. The downstream portion of the liner which would include at
least the ring 40, consitutes the dilution zone.
The sections 36, 38, 39, 40, and 12 of the liner may be connected
by suitable means to admit film cooling air to flow along the inner
surface of the liner, as is well known. Means for admission of
primary or combustion air to the combustion zone of the liner are
indicated schematically as by small ports 42 in the dome and 43 in
ring 38. A ring of large air ports 44 in the ring 40 serve to admit
dilution air to the downstream portion of the combustion liner.
Such combustion liner structure is well understood by those skilled
in the art and will not be further described here. Mention may be
made of the following U.S. patents which disclose combustion
apparatus having combustion liners of the type referred to:
Gaubatz, U.S. Pat. No. 2,699,040, Jan. 11, 1955; Dougherty, U.S.
Pat. No. 2,748,567, June 5, 1956; Hayes. U.S. Pat. No. 2,768,497,
Oct. 30, 1956; Tomlinson, U.S. Pat. No. 3,064,424, Nov. 20, 1962;
and Hayes, U.S. Pat. No. 3,064,425, Nov. 20, 1962. It will be
understood that these patents show combustion apparatus with plural
liners, but this does not affect the basic structure of the liner
or the principles of operation of the combustion apparatus.
Attention may also be invited to Amann et al. U.S. Pat No.
3,116,605, Jan. 7, 1964, and Collman et al. U.S. Pat. No.
3,267,674, Aug. 23, 1966, which structurally disclose regenerative
gas turbine engines of the type illustrated schematically in FIG.
1, and also show combustion apparatus of the type referred to.
As will be apparent from what has been said above, my invention
relates to the arrangement for conducting the air from the
compressor and heat exchanger to the combustion apparatus. This may
be expressed concisely as follows: A portion of the output of
compressor 2 is directed through the first compressed air conduit 6
into the forward end of the combustion case 10 so as to flow into
the forward or combustion zone of the combustion liner. The
remainder of the air is directed through the second conduit 8, heat
exchanger 27, and conduit 28 to the downstream or dilution end of
the case 10 so as to flow primarily through the dilution ports 44.
The unheated compressed air thus enters the combustion apparatus at
the space 46 and flows rearwardly and through the ports 42 and 43,
while the heated compressed air enters the combustion apparatus at
the space 47 and flows forwardly along the liner and into the ports
44. It would, of course, be possible to provide a complete or
partial barrier between the outer surface of the liner 11 and the
inner surface of the case 10 to block or impede flow between the
spaces 47 and 46 along the outside of the combustion liner.
However, I do not believe that such structure is needed, and prefer
to omit it.
There does need to be some arrangement for determining the relative
portions of the compressor discharge which enters case 10 through
the conduits 6 and 28. Since there is a slight pressure drop in the
regenerator, there needs to be some resistance to flow through the
conduit 6, either by the the supper of the conduit or
otherwise.
In practicing my invention, I deem it highly desirable to provide
for variably dividing the air between the conduits 6 and 8 in
accordance with engine operating conditions and, for this reason, I
have indicated the valve 4 which acts as a flow splitter to control
the relative flow through the regenerator and by-passing the
regenerator.
The structure of such a valve is merely a matter of mechanics of
construction, and the details are quite immaterial to my invention.
However, to clarify what is intended, a suitable valve structure is
illustrated somewhat schematically in FIGS. 2 and 3. As illustrated
in these figures, the valve 4 includes a body bounded by a flat
upper wall 54 and lower wall 55, with side walls 56 defining with
upper and lower walls an entrance from the conduit 3 and the outlet
to the conduits 6 and 8, generally as illustrated. A flow splitting
vane 58 is integral with a shaft 59 rotatably mounted in the walls
54 and 55 immediately adjacent the wall 56 between outlets 6 and 8.
The upper end of shaft 59 projects through wall 54 and is splined
at 60 to receive a control arm 62 retained by a cap screw 63 and a
washer. The outer end of arm 62 has a drilled hole 64 for
connection of a suitable control linkage. The control linkage,
which may be of any desired nature and may incorporate servos if
desired, is indicated in FIG. 1 by the broken line 66 connecting
the power control lever 35, fuel control valve 31, and air control
valve 4. In practice, there may be some cam arrangement or the
equivalent to cause the position valve member 58 to vary in desired
relation to the opening of the fuel valve which determines the
amount of fuel flowing to nozzle 34. By varying the fraction of the
engine air flow which proceeds through conduit 6, the efficiency of
the engine under various conditions of operation may be improved
over what it would be if the division of the air is fixed.
In a regenerative engine of the type described, I consider it to be
best that approximately 10 percent of the air flow through conduit
6 under idling conditions of engine operation. When fuel flow is
increased to accelerate the engine and the ratio of fuel to air in
the combustion zone would otherwise tend to diminish, it may be
deisrable to open the valve to pass approximately 30 percent of the
air through conduit 6. Under normal high power operation of the
regenerative engine, approximately 20 percent of the air may
preferably be supplied through conduit 6, with the remaining 80
percent being heated in the heat exchanger 23.
The by-passing of the regenerator will result in some increase in
fuel consumption. However, the substantial decrease in maximum
temperature in the primary combustion zone will beneficially reduce
the formation of nitrogen oxides in the engine.
The detailed description of preferred embodiments of the invention
for the purpose of explaining the principles thereof is not to be
considered as limiting or restricting the invention, since many
modifications may be made by the exercise of skill in the art
without departing from the scope of the invention.
* * * * *