U.S. patent application number 10/189711 was filed with the patent office on 2004-01-08 for injector apparatus and method for combusting a fuel for a gas powered turbine.
Invention is credited to Farhangi, Shahram.
Application Number | 20040003598 10/189711 |
Document ID | / |
Family ID | 29999705 |
Filed Date | 2004-01-08 |
United States Patent
Application |
20040003598 |
Kind Code |
A1 |
Farhangi, Shahram |
January 8, 2004 |
Injector apparatus and method for combusting a fuel for a gas
powered turbine
Abstract
A combustor for a gas powered turbine which employs a hypergolic
or high energy air stream and an injector design to mix fuel with
the high energy hypergolic air stream faster than the combustion
rate of the fuel. A heat exchanger and a catalyst combusts a first
portion of fuel in air without the production of undesired chemical
species. A gas powered turbine requires expanding gases to power
the turbine fans or blades. Fuel is generally combusted to produce
the required gases. A catalyst is employed to lower the combustion
temperature of the fuel. The catalyst is placed on a set of tubes
in a heat exchanger such that a portion of the thermal energy may
be transferred to the air before it engages the catalyst. After
encountering the catalyst, the fuel that was combusted increases
the temperature of the air to an auto-ignition temperature so that
no other ignition source is needed to combust additional fuel added
later. Therefore, as the air exits the heat exchanger, it enters a
main combustion chamber and is mixed with a second portion of fuel
at a rate that is greater than the combustion reaction rate of the
fuel.
Inventors: |
Farhangi, Shahram; (Woodland
Hills, CA) |
Correspondence
Address: |
Mark D. Elchuk
P.O. Box 828
Bloomfield Hills
MI
48303
US
|
Family ID: |
29999705 |
Appl. No.: |
10/189711 |
Filed: |
July 3, 2002 |
Current U.S.
Class: |
60/777 ;
60/723 |
Current CPC
Class: |
F23R 3/40 20130101 |
Class at
Publication: |
60/777 ;
60/723 |
International
Class: |
F23R 003/40 |
Claims
What is claimed is:
1. A combustion system for use in a gas powered turbine which
combusts a fuel in the presence of air while substantially
eliminating nitrous oxide emissions, comprising: a pre-heater to
heat a volume of an oxidizer to form a volume of high energy; an
injector member to inject a fuel, including a high temperature,
into said volume of high energy oxidizer; an injector port, defined
by said injector member, to provide the fuel to said volume of high
energy oxidizer before a substantial portion of the fuel combusts;
and wherein substantially all the fuel provided through said
injector port reaches its said high temperature at substantially
the same time.
2. The combustion system of claim 1, wherein said pre-heater
comprises: a fuel supply system to provide a fuel to said volume of
oxidizer: a heat exchanger including: a catalyst pathway extending
along a first axis; a cooling pathway extending along a second
axis; wherein said catalyst pathway is in thermal contact with said
cooling pathway; wherein the oxidizer is adapted to first flow
through said cooling pathway and then through said catalyst
pathway; a catalyst, placed within said catalyst pathway, and
adapted to combust the fuel with said volume of oxidizer; and
wherein said volume of oxidizer is adapted to first flow past said
catalyst pathway and through said cooling pathway, thereby
receiving thermal energy from said catalyst pathway.
3. The combustion system of claim 2, wherein said catalyst pathway
comprises a plurality of catalyst tube, that form a plurality of
catalyst tube columns each spaced apart transversally to said first
axis and which define a plurality of channels adapted for allowing
the oxidizer to flow therethrough; wherein said cooling pathway
comprises a plurality of cooling tubes that form a plurality of
cooling tube columns each spaced apart transversally to said second
axis; and wherein said cooling tubes extend substantially adjacent
said catalyst tubes along said second axis for at least a portion
of the length of said catalyst tubes.
4. The combustion system of claim 1, further comprising: at least a
first and a second of said injector ports; a first fuel stream
produced by said first injector port; a second fuel stream produced
by said second injector port; wherein said first fuel stream and
said second fuel stream impinge into one another to form a fuel
plume prior to intersecting the high energy air.
5. The combustion system of claim 4, wherein said first fuel stream
and said second fuel stream intersect at an angle between about
20.degree. and about 150.degree..
6. The combustion system of claim 4, further comprising: a fuel
path formed in said injector member such that the first fuel stream
and the second fuel stream provided by said first and second
injector ports intersect to produce said fuel plume.
7. The combustion system of claim 1, wherein said injector port is
substantially rectangular in shape such that a fuel stream is
flattened as said fuel stream exits said injector port.
8. A gas powered turbine, comprising: a compressor to produce
compressed atmospheric air to provide an oxidizer for the gas
powered turbine; a combustion system for mixing and combusting a
fuel injected into the compressed atmospheric air to produce an
expanding gas; a turbine fan which is powered by the expanding
gases: wherein said combustion system comprises: a pre-heat area; a
first fuel line to supply a first portion of fuel to the compressed
atmospheric air which is combusted in the pre-heat area to heat the
compressed atmospheric air to a hypergolic temperature so as to
produce hypergolic air; a second fuel line to supply a second
portion of fuel to the hypergolic air; an injector system to
provide said second portion of fuel to said hypergolic air before
any substantial portion of said second portion of fuel combusts;
and wherein substantially all of said second portion of fuel
combusts at substantially the same time such that the gas powered
turbine emits substantially no nitrous oxide compounds.
9. The turbine of claim 8, wherein said pre-heat area includes a
heat exchanger including: a catalyst pathway extending along a
first axis; a cooling pathway extending along a second axis which
is parallel to said first axis; wherein said catalyst pathway forms
a plurality of columns spaced transversally to said first axis and
defining a plurality of channels; and wherein said cooling pathway
extends a distance along said catalyst pathway and generally
perpendicular to said channels.
10. The turbine of claim 9, wherein said catalyst pathway includes
a plurality of catalyst tubes and said cooling pathway includes a
plurality of cooling tubes.
11. The turbine of claim 8, further comprising: a pre-mix area for
mixing the fuel from said first fuel supply with the air before the
air enters the pre-heat area; a main injector plate comprising at
least a first and a second of said injectors; and a combustion area
wherein said second supply of fuel is combusted.
12. The turbine of claim 11, further comprising: a first fuel
stream produced by said first injector port; a second fuel stream
produced by said second injector port; wherein said first fuel
stream and said second fuel stream impinge into one another forming
a fuel plume prior to intersecting the hypergolic air.
13. The turbine of claim 12, wherein said first fuel stream and
said second fuel stream intersect at an angle between about
20.degree. and about 150.degree..
14. The turbine of claim 12, further comprising a fuel path formed
in said main injector plate such that fuel provided by said first
and second injector ports intersects to produce said fuel
plume.
15. The turbine of claim 8, wherein said injector port is
substantially rectangular in shape such that a fuel stream is
flattened as said fuel stream exits said injector port.
16. A method of combusting a fuel for a gas powered turbine in the
presence of atmospheric air while substantially eliminating the
emission of nitrous oxide compounds, the method comprising:
producing an auto-ignition air stream wherein a fuel homogeneously
combusts spontaneously upon reaching the temperature of said
auto-ignition air stream; providing a first portion of the fuel to
said auto-ignition air stream; mixing said first portion of fuel
with said auto-ignition air stream before substantially any of said
first portion of fuel combusts to thereby substantially eliminate
emission of nitrous oxide compounds.
17. The method of claim 16, further comprising: producing an
expanding gas by combusting said first portion of fuel in said
auto-ignition air-stream, said expanding gas occurring when said
portion of fuel in said auto-ignition air-stream combusts upon
reaching the temperature of the auto-ignition air stream.
18. The method of claim 17, further comprising powering a turbine
with said expanding gas.
19. The method of claim 16, wherein said auto-ignition air stream
has a temperature between about 1400.degree. F. and 1600.degree.
F.
20. The method of claim 16, wherein mixing said first portion of
fuel further comprises: impinging a first fuel stream upon a second
fuel stream to form a fuel plume prior to intersecting the
auto-ignition air stream.
21. The method of claim 20, wherein impinging said first fuel
stream upon said second fuel stream occurs at an angle between
about 20.degree. and about 150.degree..
22. The method of claim 21, further comprising: forming said first
fuel stream and said second fuel stream as substantially flat
streams before allowing said streams to impinge one another.
23. The method of claim 16, wherein mixing said first portion of
fuel further comprises providing a substantially flat fuel stream
to said auto-ignition air stream.
24. The method of claim 16, wherein producing an auto-ignition
airstream further comprises: forming a fuel-air mixture by mixing a
second portion of fuel with a volume of air; and combusting said
second portion of fuel in said volume of air, wherein combusting
said second portion of fuel increases the temperature of said
volume of air to an auto-ignition temperature.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to gas turbine power plants,
and more particularly relates to main combustion injectors for
catalytic drive, substantially no noxious oxide emission power
plants.
BACKGROUND OF THE INVENTION
[0002] It is generally known in the art to power turbines with
gases being expelled from combustion chambers. These gas powered
turbines can produce power for many applications such as
terrestrial power plants. In the gas powered turbine a fuel, such
as a hydrocarbon (for example methane or kerosene) or hydrogen, is
combusted in an oxygen rich environment. The oxygen is generally
provided from atmospheric sources which also contains nitrogen and
other compounds. These combustion systems often have high emissions
of undesirable compounds such as nitrous oxide compounds (NOX) and
carbon containing compounds. It is generally desirable to decrease
these emissions as much as possible so that undesirable compounds
do not enter the atmosphere. In particular, it has become desirable
to reduce NOX emissions to a substantially low amount and more
preferably to a point where emissions are virtually eliminated.
Emissions of NOX are generally accepted to be non-existent if they
are equal to or less than about one part per million volume of dry
weight emissions.
[0003] In a combustion chamber, fuel, such as methane, is combusted
in atmospheric air where temperatures generally exceed about
1420.degree. C. (about 2600.degree. F.). This is especially true if
flame holding zones or high temperature pilot flames are used to
stabilize the combustion process. When temperatures are generally
above about 1420.degree. C., the nitrogen and oxygen compounds,
both present in atmospheric air, undergo chemical reactions which
produce nitrous oxide compounds. The energy provided by the high
temperatures allows the breakdown of dinitrogen and dioxygen,
especially in the presence of other materials such as various
metals, to produce NOX compounds such as NO.sub.2 and NO.
[0004] Attempts have been made to reduce production of NOX
compounds by initially heating the air before it enters the
combustion chambers to an auto-ignition temperature. If the air
enters the combustion chamber at or above an auto-ignition
temperature, then pilot flames or recirculation flame holding zones
are not necessary to combust the fuel. Auto-ignition temperatures
are usually lower than pilot flame temperatures or the temperatures
inside recirculation flame holding zones. One such method for
heating air to the auto-ignition temperature is to mix the fuel in
the air before it reaches the combustion chamber. This vitiated
air, that is air which includes the fuel, is then ignited in a
pre-burner where at least a portion of the entrained fuel is
combusted. This raises the temperature of the air before it reaches
the main combustion chamber. This decreases NOX production and
emissions substantially. Nevertheless, NOX emissions still exist
due to the initial pre-burning.
[0005] In view of the foregoing, it will be appreciated that it is
desirable to decrease or eliminate pre-burning, thereby
substantially eliminating all NOX emissions. Although the air is
heated before entering the main combustion chamber, it may still
need to be ignited in the combustion chamber to combust the
remaining fuel. Therefore, an additional flame or arc is used to
combust remaining fuel in the main combustion chamber. This reduces
the temperature that the igniter must be at but still increases the
temperature of the combustion chamber. In addition, no fuel is
added to the air as it enters the combustion chamber. Rather all
the fuel has already been entrained in the air before it enters the
combustion chamber to be combusted. This greatly reduces control
over where combustion occurs and the temperature in the combustion
chamber.
[0006] Other attempts to lower NOX emissions include placing
catalysts in catalytic converters on the emission side of the
turbines. This converts the NOX compounds into more desirable
compounds such as dinitrogen and dioxygen. These emission side
converters, however, are not one hundred percent efficient thereby
still allowing NOX emissions to enter the atmosphere. The emission
converters also use ammonia NH.sub.3, gas to cause the reduction of
NOX to N.sub.2. Undesirably, some of this ammonia is discharged
into the atmosphere. Also, these converters are expensive and
increase the complexity of the turbine and power production
systems. Therefore, it is also desirable to eliminate the need for
emission side catalytic converters.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a combustor and a
combustion chamber for a gas powered turbine. A heat exchanger and
a catalyst combust a first portion of fuel intermixed with air
without the production of undesired chemical species. The gas
powered turbine requires expanding gases to power the turbine fans
or blades. Fuel is generally combusted to produce the required
gases. A catalyst is employed to lower the combustion temperature
of the fuel. The catalyst is placed on a set of tubes in a heat
exchanger such that a portion of the thermal energy may be
transferred to the air before it engages the catalyst. After
encountering the catalyst, the fuel that was combusted increases
the temperature of the air to an auto-ignition temperature so that
no other ignition source is needed to combust additional fuel added
later. Therefore, as the air exits the heat exchanger, it enters a
main combustion chamber, is mixed with a second portion of fuel
where it is auto-ignited and burned.
[0008] One preferred embodiment of the present invention includes a
combustion system for use in a gas powered turbine which combusts a
fuel in the presence of air while substantially eliminating nitrous
oxide emissions. The system includes a pre-heater to heat
compressed air to form a hypergolic air. An injector plate injects
a fuel into the hypergolic air. An injector port, defined by the
injector plate, provides the fuel to the hypergolic air before a
substantial portion of the fuel combusts. Substantially all the
fuel provided through the injector port reaches its hypergolic
temperature at substantially the same time.
[0009] A second preferred embodiment of the present invention
provides a gas powered turbine. The gas powered turbine includes a
compressor that produces compressed atmospheric air to provide an
oxidizer for the gas powered turbine. A combustion system mixes and
combusts a fuel injected into the compressed atmospheric air to
produce an expanding gas. A turbine fan is powered by the expanding
gases.
[0010] The combustion system of the second preferred embodiment
includes a pre-heat area, a first fuel line, a second fuel line,
and an injector system. The first fuel line supplies a first
portion of fuel to the compressed atmospheric air which is
combusted in the pre-heat area to heat the compressed atmospheric
air to a hypergolic temperature so as to produce hypergolic air.
The second fuel line supplies a second portion of fuel to the
hypergolic air. The injector system provides the second portion of
fuel to the hypergolic air before any substantial portion of the
second portion of fuel combusts. In addition, substantially all of
the second portion of fuel combusts at substantially the same time
such that the turbine emits substantially no nitrous oxide
compounds.
[0011] The present invention provides for a new and unique method
of combusting a fuel for a gas powered turbine in the presence of
atmospheric air while substantially eliminating the emission of
nitrous oxide compounds. The method includes providing a
pre-heater. A first fuel-air mixture is formed by mixing a first
portion of the fuel and the air. An auto-ignition air stream is
produced by combusting the first fuel-air mixture. A second portion
of the fuel is then added to the auto-ignition air stream. The
second portion of fuel is then mixed with the auto-ignition air
stream before substantially any of the second portion of fuel
combusts.
[0012] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0014] FIG. 1 is a perspective view of a gas powered turbine
including a combustor in accordance with the present invention;
[0015] FIG. 2 is a partial cross-sectional perspective view of a
single combustor;
[0016] FIG. 3 is a detailed, partial cross-sectional, perspective
view of a portion of the heat exchanger; and
[0017] FIG. 4 is a detailed, cross-sectional view of a portion of
the main injectors according to the present invention;
[0018] FIG. 5a is a detailed, elevational view of the downstream
side of the main injector plate according to a first embodiment of
the present invention;
[0019] FIG. 5b is a detailed cross-sectional view of the main
injector plate taken along line 5b in FIG. 5a;
[0020] FIG. 6a is a detailed elevational view of a downstream side
of the main injector plate according to a second embodiment of the
present invention;
[0021] FIG. 6b is a detailed cross-sectional view of the injector
plate taken along line 6b in FIG. 6a; and
[0022] FIG. 7 is a detailed, partial cross-sectional, perspective
view of a portion of the heat exchanger according to the second
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0024] Referring to FIG. 1, a gas powered turbine in accordance
with a preferred embodiment of the present invention is shown. The
gas powered turbine 10 may use several different gaseous fuels,
such as hydrocarbons (including methane and propane) and hydrogen,
that are combusted and that expand to move portions of the gas
powered turbine 10 to produce power. An important component of the
gas powered turbine 10 is a compressor 12 which forces atmospheric
air into the gas powered turbine 10. Also, the gas powered turbine
10 includes several combustion chambers 14 for combusting fuel. The
combusted fuel is used to drive a turbine 15 including turbine
blades or fans 16 which are axially displaced in the turbine 15.
Generally, a plurality of turbine fans 16 are incorporated,
however, the actual number depends upon the power the gas powered
turbine 10 is intended to produce. Only a single turbine fan is
illustrated for clarity.
[0025] In general, the gas powered turbine 10 ingests atmospheric
air, combusts a fuel in it, and powers the turbine fans 16.
Essentially, air is pulled in and compressed by the compressor 12,
which generally includes a plurality of concentric fans which grow
progressively smaller along the axial length of the compressor 12.
The fans in the compressor 12 are all powered by a single axle. The
high pressure air then enters the combustion chambers 14 where fuel
is added and combusted. Once the fuel is combusted, it expands out
of the combustion chamber 14 and engages the turbine fans 16 which,
due to aerodynamic and hydrodynamic forces, spins the turbine fans
16. The gases form an annulus which spins the turbine fans 16,
which are in turn affixed to a shaft (not shown). Generally, at
least two turbine fans 16 are incorporated. One or more of the
turbine fans 16 engage the same shaft that the compressor 12
engages. The gas powered turbine 10 is self-powered since the
spinning of the turbine fans 16 also powers the compressor 12 to
compress air for introduction into the combustion chambers 14.
Other turbine fans 16 are affixed to a second shaft 17 which
extends from the gas powered turbine 10 to power an external
device. After the gases have expanded through the turbine fans 16,
they are expelled out through an exhaust port 18. It will be
understood that gas powered turbines are used for many different
applications such as engines for vehicles and aircraft or for power
production in terrestrially based gas powered turbine power
system.
[0026] The gases which are exhausted from the gas powered turbine
10 include many different chemical compounds that are created
during the combustion of the atmospheric air in the combustion
chambers 14. If only pure oxygen and pure hydrocarbon fuel were
combusted, absolutely completely and stoichiometrically, then the
exhaust gases would include only carbon dioxide and water.
Atmospheric air, however, is not pure oxygen but rather includes a
majority nitrogen and other trace compounds. Therefore, in the high
energy environment of the combustion chambers 14, many different
compounds may be produced. All of these compounds are exhausted
from the exhaust port 18. It is generally known in the art that an
equivalence ratio is determined by dividing the actual ratio of
fuel and air by a stoichiametric ratio of fuel to air (where there
is not an excess of one starting material). Therefore, a completely
efficient combustion of pure fuel and oxygen air would equal an
equivalence ratio of one. It will be understood that although
atmospheric air in a hydrocarbon fuel may be preferred for economic
reasons other oxidizers and fuels may be provided. The air simply
provides an oxidizer for the fuel to be combusted in. Therefore,
other oxidizing materials such as pure oxygen may be used in the
gas powered turbine 10. In addition, other fuels may be combusted
which are not necessarily simply hydrocarbons. Regardless, the
present invention may be used with any oxidizer or fuel which is
used to power the gas powered turbine 10.
[0027] It will be understood that the gas powered turbine 10 may
include more than one combustion chamber 14. A reference to only
one combustion chamber 14, herein, is merely for simplifying the
following discussion. With reference to FIG. 2, an exemplary
combustion chamber 14 is illustrated. The combustion chamber may
comprise any appropriate combustion chamber such as the one
described in U.S. patent application Ser. No. 10/120,268 filed Apr.
10, 2002 entitled, "A Catalytic Combustor For Substantially
Eliminating Nitrous Oxide Emissions," incorporated herein by
reference. The combustion chamber 14 includes a premix section or
area 30, a heat exchange or pre-heat section 32, generally enclosed
in a heat exchange chamber 33, and a main combustion section 34. A
first or premix fuel line 36 provides fuel to the premix area 30
through a fuel manifold 37 while a second or main fuel line 38
provides fuel to the main combustion section 34 through a main
injector 52. Positioned in the premix area 30 is a premix injector
40 that injects fuel from the first fuel line 36 into a premix
chamber 42. Air from the compressor 12 enters the premix area 30
through a cooling tube 44 of a heat exchanger or pre-heater 45
(detailed in FIG. 3). The premix chamber 42 encompasses a volume
between the premix injector 40 and the exit of the cooling tubes
44.
[0028] With further reference to FIG. 2, a plurality of catalytic
heat exchange or catalyst tubes 48 extend into the heat exchange
area 32. The heat exchange tubes 48 are spaced laterally apart. The
heat exchange tubes 48, however, are not spaced vertically apart.
This configuration creates a plurality of columns 49 of heat
exchange tubes 48. Each heat exchange tube 48, and the column 49 as
a whole, define a catalyst pathway. The columns 49, in turn, define
a plurality of channels 50 therebetween. Extending inwardly from
the walls of the heat exchange chamber 33 are directing fins (not
particularly shown). The directing fins direct the flow of air to
the top and the bottom of the heat exchange chamber 33 so that air
is directed to flow vertically through the channels 50 defined by
the heat exchange tubes 48.
[0029] Near the ends of the heat exchange tubes 48, where the heat
exchange tubes 48 meet the main combustion section 34, is a main
injector 52. The second fuel line 38 provides fuel to the main
injector 52 so that fuel may be injected at the end of each heat
exchange tube 48. Spaced away from the main injector plate 52,
towards the premix area 30, is an intra-propellant plate 54. The
intra-propellant plate 54 separates the air that is traveling
through the channels 50 and the fuel that is being fed to the fuel
manifold region 56 between the main injector face 52 and
intra-propellant plate 54. It will be understood that the
intra-propellant plate 54 is effectively a solid plate, though not
literally so in this embodiment. Because the heat exchange tubes 48
are spaced apart the intra-propellant plate 54 is segmented wherein
one portion of the intrapropellant plate 54 is placed in each
channel 50 between two columns 49.
[0030] Air that exits out the heat exchange tubes 48 is entrained
with fuel injected from an injector port 60 (illustrated more
clearly herein) in the main injector plate 52 and this fuel then
combusts in the main combustion section 34. The main combustion
section 34 directs the expanding gases of the combusted fuel to
engage the turbine fans 16 so that the expanded gases may power the
turbine 10.
[0031] Turning to FIG. 3, an enlarged portion of the heat exchanger
45 including a catalyst is shown. Although the heat exchanger 45
includes a large plurality of tubes, as generally shown in FIG. 2,
only a few of the heat exchange tubes 48 and cooling tubes 44 are
illustrated for greater clarity. The heat exchanger 45 includes a
plurality of cooling tubes 44 disposed parallel to and closely
adjacent the heat exchange tubes 48. Each of the cooling tubes 44
and the heat exchange tubes 48 have a generally rectangular cross
section and can be made of any generally good thermally conductive
material. Preferably, the heat exchange tubes 48 and the cooling
tubes 44 are formed out of stainless steel. It will be appreciated
that while the cooling tubes 44 and the heat exchange tubes 48 are
shown as being substantially square, the cross-sectional shape of
the components could comprise a variety of shapes other than
squares. It is believed, however, that the generally square shape
will provide the best thermal transfer between the tubes 44 and
48.
[0032] The cooling tubes 44 extend parallel to the heat exchange
tubes 48 for a portion of the length of the heat exchange tubes 48.
The cooling tubes 44 extend between the columns 49 of the heat
exchanger tubes 48. The cooling tubes 44 and the heat exchange
tubes 48 form the heat exchanger 45 which can provide a
surface-to-surface exchange of heat. It will be understood,
however, that air traveling in the channels 50 between the heat
exchange tubes 48 will also become heated due to the heat
transferred from the heat exchange tubes 48 to the air in the
channels 50.
[0033] Referring further to FIG. 3, fuel injector ports 60 are
formed in the main injector 52. The injector ports 60 may be
provided in any appropriate number, however, preferably there is at
least one injector port 60 for each heat exchange tube 48, and more
preferably at least two injector ports 60 for each heat exchange
tube 48. The fuel is provided to the manifold region 56 which is
bound by the inter-propellant plate 54, the main injector plate 52,
and a manifold plate 61. The manifold plate 61 may underlay,
overlay, or both the manifold region 56. This provides fuel to each
of the injector ports 60 without requiring an individual fuel line
to each injector port 60. Therefore, as air exits the heat exchange
tube 48, fuel is injected from the injector port 60 to the stream
of air emitted from each heat exchange tube 48. In this way, the
fuel can be very efficiently and quickly distributed throughout the
air flowing out of the heat exchanger 45, as discussed further
herein.
[0034] On the interior walls of each heat exchange tube 48 is
disposed a coating of a catalyst. The catalyst may be any
appropriate catalyst that is able to combust a hydrocarbon fuel,
but preferably includes a mixture of platinum and palladium. The
catalyst is able to combust a hydrocarbon fuel, such as methane,
without the presence of a flame or any other ignition source. The
catalyst is also able to combust the fuel without generally
involving any side reactions. Therefore, the combustion of fuel
does not produce undesired products. It will be understood that if
the fuel is not a hydrocarbon then a different, appropriate
catalyst is used. The catalyst allows combustion of the fuel
without an additional heat source.
[0035] After the air enters the premix chamber 42, it then flows
out through the pathway formed by the heat exchange tubes 48. In
the heat exchange tubes 48, the fuel in the air combusts as it
engages the catalyst which has been coated on the inside walls of
the heat exchange tubes 48. As the fuel combusts, the temperature
of the air rises to between about 768.degree. C. and 930.degree. C.
(between about 1400.degree. F. and about 1700.degree. F.). As the
temperature of the air rises, it becomes highly energetic to form
high energy air, wherein high energy air exits the heat exchange
tubes 48. The temperature the high energy air reaches in the heat
exchange tubes 48 is at least the hypergolic or auto-ignition
temperature of the fuel being used in the gas powered turbine 10.
Therefore, the high energy air that exits the heat exchange tubes
48 is, and may also be referred to as, hypergolic or auto ignition
air. The auto-ignition temperature of the air is the temperature
that the air may be at or above so that when more fuel is injected
into the hypergolic air the fuel ignites automatically without any
other catalyst or ignition source.
[0036] Additional fuel is injected through the main injector 52 as
the air exits the heat exchange tubes 48 and enters the main
combustion section 34. The fuel injected from the main injector 52
is injected through the individual injector ports 60. As described
above, the ratio of heat exchange tubes 48 to fuel injector ports
60 is preferably about one to one. It will be understood, however,
that a different ratio of heat exchange tubes 48 to fuel injector
ports 60 may be used to suit a specific application. Therefore, all
of the air exiting the heat exchanger 45 is thoroughly mixed with
fuel. Any additional fuel to power the gas powered turbine 10 is
injected at this point, such that fuel is only added to the air at
the premix chamber 42 and from the injector parts 60.
[0037] The gas powered turbine 10 operates as generally described
below. Air is forced from the compressor 12 into the heat exchange
chamber 33. The air then travels through the channels 50 and
through the cooling tubes 44 into the premix chamber 42. At this
point a first or premix portion of fuel is intermixed with the air.
The air then travels downstream through the heat exchange tubes 48
until the air is expelled from the heat exchange tubes 48 past the
main injector 52 and to the combustion area 34 as hypergolic
air.
[0038] As the air travels through the heat exchange tubes 48, the
fuel that was entrained in the air in the premix chamber 42 is
combusted by the catalyst. This raises the temperature of the air
from the temperature that it enters the heat exchange chamber 33.
In particular, the temperature of the air is raised to preferably
between about 700.degree. C. and 880.degree. C. (between about
1300.degree. F. and about 1600.degree. F.). This temperature is
generally the hypergolic temperature so that the fuel combusts
spontaneously when added through the injector port 60. It will be
understood that different fuels have different hypergolic
temperatures. Therefore, the amount of fuel added in the premix
section 42 may be altered to determine the temperature of the air
exiting the heat exchange tubes 48.
[0039] With reference to FIG. 4, the heat exchange tubes 48 extend
from an upstream side 70 through the intra-propellant plate 54 and
terminate into the main injector 52. A face of the injector 52a is
downstream of the heat exchange tubes 48. Fuel is provided through
the main fuel line 38 to the manifold region 56 which is the area
between the intra-propellant plate 54 and the main injector 52.
Although only one main fuel line 38 is illustrated, it will be
understood that more than one main fuel line may be provided.
Formed in the main injector plate 52 are oxidizer passages or
pathways 72 which are extensions of the heat exchange tubes 48
formed in the main injector plate 52. The hypergolic air from the
heat exchange tubes 48 passes through the oxidizer pathways 72 and
exits into the main combustion area 34.
[0040] Extending back from the injector port 60 is a fuel injection
path 74. Each fuel injector port 60 includes at least one fuel
pathway 74. The fuel pathway 74 is preferably a bore formed in the
main injector plate 52 to allow access between the fuel manifold
region 56 so that the fuel which is provided to the fuel manifold
region 56 from the main fuel line 38 can reach the combustion area
34. Generally, the fuel pathways 74 are formed in the main injector
plate 52 and the spaces or lands between the oxidizer pathways 72
which extend from the heat exchange tubes 48.
[0041] The fuel exits the injector ports 60 as a fuel stream 76 in
line with the fuel pathway 74 provided in the main injector plate
52. Preferably, the fuel stream 76 has a half angle of between
about 40.degree. and about 50.degree. and preferably of about
45.degree.. Therefore as two of the fuel streams 76 intersect, in
an area of the combustion chamber 34, which is downstream of the
face 52a of the injector plate 52, the streams intersect at about
an 80.degree. to 100.degree. angle. It will be understood, however,
that the fuel streams 76 may intersect at a slightly different
angle. For example, the fuel streams may intersect at angles
ranging between about 20.degree. and about 150.degree..
[0042] With reference to FIGS. 5a and 5b, a first embodiment of the
fuel injector port 60 is illustrated. The hypergolic air, which
acts as an oxidizer, exits from the oxidizer pathways 72. As this
is happening, fuel exits from the injector ports 60 and is
transmitted along fuel streams 76. Because the two fuel streams 76
are angled, they intersect at a point downstream of the oxidizer
pathways 72 and between the oxidizer pathways 72 in a land region
77. As discussed above, preferably two fuel streams 76 intersect at
an angle of about 90.degree.. When this intersection occurs, the
two fuel streams interrupt each other and produce a fuel plume 80
which spreads into the appropriate oxidizer pathways 72. The fuel
plume 80 is a substantially and finely atomized from the fuel
streams 76 that are spreading out extremely rapidly. This allows
the fuel in the fuel streams 76 is to intermix very quickly with
the hypergolic air as it exits the oxidizer pathways 72.
[0043] As discussed above, the air exits the oxidizer pathways 72
at approximately the auto-ignition or hypergolic temperature of the
fuel in the fuel streams 76. Therefore, as soon as the fuel from
the fuel streams 76 is raised to the temperature of the hypergolic
air exiting the oxidizer pathways 72, the fuel will ignite.
Therefore, if the fuel is able to mix substantially well with the
air as it exits the oxidizer pathways 72, the entire amount of fuel
injected with the fuel streams 76 will ignite at substantially the
same time. When this occurs, the ignition of fuel from the fuel
streams 76 across the face 52a of the injector plate 52 will be
substantially constant and equal. Therefore, there are
substantially no hot spots created, thus keeping the temperature of
the combustion chamber 34 to one which allows substantially no
nitrous oxide compounds to be produced. Because the fuel in the
fuel plume 80 is spreading out so quickly into the high energy air
exiting the oxidizer pathways 72, the fuel mixes with the
hypergolic air and becomes heated to the hypergolic temperature
faster than the ignition or combustion rate of the fuel. Therefore,
substantially all of the fuel that is injected from the injector
port 60 reaches the hypergolic temperature at the same time.
Therefore, substantially all the fuel combusts at substantially the
same time, not allowing the creation of any discrete hot spots.
[0044] With references to FIGS. 6a and 6b, a fuel injector port 90
according to a second preferred embodiment of the present invention
is illustrated. With this embodiment, heated air still exits the
main injector 52 through the oxidizer pathways 72. Fuel streams 76
are also produced as fuel exits injector ports 90. The injector
ports 90 are not circular but rather are generally rectangle in
shape having a height of H which substantially greater than a width
W. The height H of the injector port 90 extends substantially
parallel to the height of the oxidizer pathways 72. Therefore, a
fuel stream or fan 92 is produced by the fuel injectors 90 that is
substantially spread out or flattened, as it exists the injector
port 90, as opposed to the fuel stream 76 described previously
herein.
[0045] Fuel may enter the fuel pathway 74 through any appropriately
shaped port but as the pathway 74 nears the injector port 90, the
pathway becomes substantially rectangular having a height H which
is much greater than a width W. With particular reference to FIG.
6b, the upstream side of the main injector plate 52 includes an
inlet port 94, that is substantially circular in shape.
Nevertheless, the injector port 90 is substantially rectangular in
shape. The fuel stream 92 this produces is already substantially
spread out or thinned before it reaches an intersection point with
another fuel stream 92. As two fuel streams 92 intersect, they
produce a fuel plume 96 which allows the fuel provided through the
injector ports 90 to be mixed with the hypergolic air exiting the
oxidizer pathways 72 before the fuel, provided in the fuel streams
92, reaches its ignition temperature.
[0046] This allows a substantial intermixing of the fuel with the
air exiting the oxidizer pathways 72 before the fuel combusts so
that the combustion in the combustion chamber 34, across the face
of 52a of the main injector plate 52, is substantially even. This
does not generally allow hot spots in the combustion area 34 to
form, thereby substantially eliminating the production of NOX
chemicals. It will be appreciated that in this second embodiment,
opposing fuel fans 92 are not necessary to provide an appropriate
fuel plume 96. Because the injector port 90 produces a fuel fan 92
which is already substantially spread out and dispersed, the
impingement of two fuel streams is not generally necessary.
[0047] As discussed above, the air that exits the heat exchanger 45
is at the auto-ignition or hypergolic temperature of the fuel used
in the gas powered turbine 10. Therefore, as soon as the fuel
reaches the temperature of the air, the fuel ignites. Since the
fuel has been thoroughly mixed with the air, using the fuel
injector ports 60 and 90, the combustion of the fuel is nearly
instantaneous and will not produce any localized or discrete hot
spots. Since the fuel is so well mixed with the air exiting the
heat exchanger 45, there will be no one point or area which has
more fuel than any other point, which could also create hot spots
in the main combustion section 34. Therefore, the temperature of
the air coming from the main injector 52 and into the main
combustion section 34 is substantially uniform. During operation of
the gas powered turbine 10, the fuel's characteristic mixing rate
is shorter than the combustion rate of the fuel.
[0048] The temperature of the air, after the additional fuel has
been combusted from the main injector 52, is between about
1315.degree. C. and 1595.degree. C. (about 2400.degree. F. and
about 2800.degree. F.). Preferably, the temperature, however, is
not more than about 1426.degree. F. (about 12600.degree. F.).
Different fuel to air ratios may be used to control the temperature
in the main combustion section 34. The main combustion section 34
directs the expanding gases into a transition tube (not shown) so
that it will engage the turbine fans 16 in the turbine area 15 at
an appropriate cross sectional flow shape.
[0049] The use of the heat exchanger 45 raises the temperature of
the air to create hot or heated air. The hot air allows the
catalyst to combust the fuel that has been entrained in the air in
the premix chamber 42 without the need for any other ignition
sources. The catalyst only interacts with the hydrocarbon fuel and
the oxygen in the air to combust the fuel without reacting any
other chemical species. Therefore, the products of the combustion
in the heat exchange tubes 48 are substantially only carbon dioxide
and water due to the catalyst placed therein. No significant
amounts of other chemical species are produced because of the
catalyst. Also, the use of the heat exchange tubes 48, with a
catalyst coated therein, allows the temperature of the air to reach
the auto-ignition temperature of the fuel so that no additional
ignition sources are necessary in the main combustion section 34.
Therefore, the temperature of the air does not reach a temperature
where extraneous species may be easily produced, such as NOX
chemicals. Due to this, the emissions of the gas powered turbine 10
of the present invention has virtually no NOX emissions. That is,
that the NOX emissions of the gas powered turbine 10 according to
the present invention are estimated to be generally below about 1
part per million volume dry weight.
[0050] Also, the use of the heat exchanger 45 eliminates the need
for any other pre-burners to be used in the gas powered turbine 10.
The heat exchanger 45 provides the thermal energy to the air so
that the catalyst bed is at the proper temperature. Because of
this, there are no other areas where extraneous or undesired
chemical species may be produced. Additionally, the equivalence
ratio of the premix area is generally between about 0.20 and 0.30,
while the equivalence ratio of the main injector 52 is between
about 0.50 and about 0.60. This means that the fuel combustion will
occur as a lean mixture in both areas. Therefore, there is never an
excessive amount of fuel that is not combusted. Also, the lean
mixture helps to lower temperatures of the air to more easily
control side reactions. It will be understood that different fuel
ratios may be used to produce different temperatures. This may be
necessary for different fuels.
[0051] With reference to FIG. 7, a detail portion, similar to the
portion illustrated in FIG. 3, of an alternative preferred heat
exchanger 145 is illustrated. A premix chamber 142 allows air from
the compressor to be mixed with a first portion of fuel. Air comes
from the compressor and travels through a cooling fin 144 rather
than through a plurality of cooling tubes 44, as discussed above in
relation to the first embodiment. The cooling fin 144 is defined by
two substantially parallel plates 144a and 144b. It will be
understood, however, that other portions, such as a top 144c and a
bottom 144d will be included to enclose the cooling fin 144.
Additionally, a heat exchange or catalyst fin 148 is provided
rather than heat exchange tubes 48, as discussed above in the first
embodiment. Again, the catalyst fin 148 is defined by a top, and a
bottom, and walls wherein the walls define a column 149. Each
catalyst column 149, however, is defined by a single catalyst fin
148 rather than a plurality of catalyst tubes 48, as discussed
above. The cooling fin 144 may include a plurality of cooling fins
144. Each cooling fin 144, in the plurality, defines a cooling
pathway. Similarly, the heat exchange fin 148 may include a
plurality of heat exchange 148 fins. Each, or the plurality of, the
heat exchange fins 148 defines a heat exchange or catalyst
pathway.
[0052] Channels 150 are still provided between each of the catalyst
fins 148 so that air may flow from the compressor through the
cooling fins 144 into the premix chamber 142. Air is then premixed
with a first portion of fuel and flows back through the catalyst
fins 148 to the main injector plate 152. Injection ports 160 are
provided on the main injector plate 152 to inject fuel as the air
exits the catalyst fin 148. A suitable number of injection ports
160 are provided so that the appropriate amount of fuel is mixed
with the air as it exits the catalyst fins 148. An intra-propellant
plate 54 is also provided.
[0053] Injector ports 60 or 90 are still provided on the main
injector plate 152 to provide fuel streams 76 or 92 as heated air
exits the oxidizer paths (not particularly shown) from the catalyst
fins 148. Either of the previously described injector ports 60 or
90 may be used with the second embodiment of the heat exchanger 145
to provide a substantial mixing of the fuel with the air as it
exits the catalyst fins 148. This still allows a substantial
mixture of the fuel with the air as it exits the catalyst fins 148
before the fuel is able to reach its ignition temperature.
Therefore, the temperatures across the face of the main injector
152 and in the combustion chamber 34 are still substantially
constant without any hot spots where NOX chemicals might be
produced.
[0054] The present invention thus provides an apparatus and method
that virtually or entirely eliminates the creation of NOX
emissions. Advantageously, this is accomplished without
significantly complicating the construction of the gas powered
turbine 10 or the combustors 14.
[0055] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *