CA1190051A - Combustion turbine combustor having an improved fuel- rich fuel preparation zone - Google Patents
Combustion turbine combustor having an improved fuel- rich fuel preparation zoneInfo
- Publication number
- CA1190051A CA1190051A CA000405430A CA405430A CA1190051A CA 1190051 A CA1190051 A CA 1190051A CA 000405430 A CA000405430 A CA 000405430A CA 405430 A CA405430 A CA 405430A CA 1190051 A CA1190051 A CA 1190051A
- Authority
- CA
- Canada
- Prior art keywords
- fuel
- combustor
- combustion
- static mixing
- zone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000446 fuel Substances 0.000 title claims abstract description 98
- 238000002360 preparation method Methods 0.000 title claims abstract description 43
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 42
- 230000003068 static effect Effects 0.000 claims abstract description 24
- 239000007789 gas Substances 0.000 claims abstract description 23
- 239000000203 mixture Substances 0.000 claims description 17
- 230000009977 dual effect Effects 0.000 claims description 5
- 230000001133 acceleration Effects 0.000 claims description 4
- 230000007704 transition Effects 0.000 claims description 3
- 230000008016 vaporization Effects 0.000 claims description 3
- 238000007084 catalytic combustion reaction Methods 0.000 claims description 2
- 238000011144 upstream manufacturing Methods 0.000 claims 2
- 230000007423 decrease Effects 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 claims 1
- 230000004941 influx Effects 0.000 claims 1
- 230000000977 initiatory effect Effects 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 description 15
- 206010016754 Flashback Diseases 0.000 description 6
- 239000011800 void material Substances 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 3
- 239000008246 gaseous mixture Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 241000950314 Figura Species 0.000 description 1
- 235000008694 Humulus lupulus Nutrition 0.000 description 1
- 244000025221 Humulus lupulus Species 0.000 description 1
- SZKKRCSOSQAJDE-UHFFFAOYSA-N Schradan Chemical compound CN(C)P(=O)(N(C)C)OP(=O)(N(C)C)N(C)C SZKKRCSOSQAJDE-UHFFFAOYSA-N 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000000779 depleting effect Effects 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- RLQJEEJISHYWON-UHFFFAOYSA-N flonicamid Chemical compound FC(F)(F)C1=CC=NC=C1C(=O)NCC#N RLQJEEJISHYWON-UHFFFAOYSA-N 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229960005419 nitrogen Drugs 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000010977 unit operation Methods 0.000 description 1
- 230000003245 working effect Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/02—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration
- F23R3/16—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration with devices inside the flame tube or the combustion chamber to influence the air or gas flow
- F23R3/18—Flame stabilising means, e.g. flame holders for after-burners of jet-propulsion plants
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/36—Details, e.g. burner cooling means, noise reduction means
- F23D11/40—Mixing tubes or chambers; Burner heads
- F23D11/402—Mixing chambers downstream of the nozzle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D2209/00—Safety arrangements
- F23D2209/10—Flame flashback
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Combustion Of Fluid Fuel (AREA)
- Spray-Type Burners (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A combustion turbine combustor is provided with an improved fuel preparation zone which utilizes the ar-rangement of a static mixing structure to accelerate the flow velocity of combustible gases into a combustion zone.
The increased flow velocity reduces the potential of the combustor for flashback and enables use of a fuel-rich configuration in the combustor.
A combustion turbine combustor is provided with an improved fuel preparation zone which utilizes the ar-rangement of a static mixing structure to accelerate the flow velocity of combustible gases into a combustion zone.
The increased flow velocity reduces the potential of the combustor for flashback and enables use of a fuel-rich configuration in the combustor.
Description
1 ~g,685 COMBUSTION TURBINE COMBUSTOR HAVING AN
IMPROVED FUEL-RICH FUEL PREPARATION ZONE
BACKGROUND OF THE INVENTION
... .. .
The present invention relates to combustion tur-bines and combustors employed therein and more particular-ly to an improved fuel preparation zone structure for a pre-mixing, pre-vaporizing combus~or.
In general terms, the typical prior art combus-tion turbine comprises three sections: a compressor sec-tion, a combustor section, and a turbine section. Air drawn into the compressor section is compressed, increasing its temperature and density. The compressed air from the - compressor section flows through the combustor section where the temperature of the air mass is further increased.
From th~ combus~or section the hot pressurized gases flow ~'
IMPROVED FUEL-RICH FUEL PREPARATION ZONE
BACKGROUND OF THE INVENTION
... .. .
The present invention relates to combustion tur-bines and combustors employed therein and more particular-ly to an improved fuel preparation zone structure for a pre-mixing, pre-vaporizing combus~or.
In general terms, the typical prior art combus-tion turbine comprises three sections: a compressor sec-tion, a combustor section, and a turbine section. Air drawn into the compressor section is compressed, increasing its temperature and density. The compressed air from the - compressor section flows through the combustor section where the temperature of the air mass is further increased.
From th~ combus~or section the hot pressurized gases flow ~'
2 49,6a5 into ~he turbine section where the energy of the expanding gases is transformed into rotational motion of the turbine rotor.
A typical combustor section comprise~ a plural-5 ity of combu~tors arranged in an annular array about the circumference of the combustion turbine. In conventional combustor technology pressurized gases flowing from the compressor section are heated by a difusion flame in the combustor before passing to the turbine sec ion. In the diffusion flame technique, fuel is sprayed into the up stream end of the combustor by means of a nozzle. The ~lame i~ maintained immediately downstream of the no7zle by strong aerodynamic recirculation. The lack of thorough mixing of the fuel results in pockets of high fuel concen-tration and correspondingly high combustion reactiontemperatures, on the order of approximately 450~R.
3ecause the reaction temperature is high, hot gases flow-ing from the combustion reaction must be diluted down-stream by cool (approximately 700~R) air so as to prevent damage to turbine components positioned downstre m. In addition, the flame diffusion technique produces emissions with significant levels of undesirable chemical compounds including NOx and CO.
Increasing environmental awareness has resulted in more stringent emission s-tandards for NO~ and CO. The more stringent standards are leading to ~evelopment of improved combustor technologies. One such impro~ement is a premixing, prevaporizlng combustor. In this t~pe of combustor, fuel is sprayed into a fuel preparation zone where it is thoroughly mixed to achieve a homogeneous conentration which is everywhere within definite limits of the mean concentration. Additionally, a certain amount of the fuel is vap~rized in the fuel preparation zone.
Fuel combustion occurs at a point downstream from the fueL
preparatlon zonc. The substantially unlform fuel concen-tration achieved in the fuel preparation zone results in a uniform reaction temperature ~hich may be li.mited to .....
A typical combustor section comprise~ a plural-5 ity of combu~tors arranged in an annular array about the circumference of the combustion turbine. In conventional combustor technology pressurized gases flowing from the compressor section are heated by a difusion flame in the combustor before passing to the turbine sec ion. In the diffusion flame technique, fuel is sprayed into the up stream end of the combustor by means of a nozzle. The ~lame i~ maintained immediately downstream of the no7zle by strong aerodynamic recirculation. The lack of thorough mixing of the fuel results in pockets of high fuel concen-tration and correspondingly high combustion reactiontemperatures, on the order of approximately 450~R.
3ecause the reaction temperature is high, hot gases flow-ing from the combustion reaction must be diluted down-stream by cool (approximately 700~R) air so as to prevent damage to turbine components positioned downstre m. In addition, the flame diffusion technique produces emissions with significant levels of undesirable chemical compounds including NOx and CO.
Increasing environmental awareness has resulted in more stringent emission s-tandards for NO~ and CO. The more stringent standards are leading to ~evelopment of improved combustor technologies. One such impro~ement is a premixing, prevaporizlng combustor. In this t~pe of combustor, fuel is sprayed into a fuel preparation zone where it is thoroughly mixed to achieve a homogeneous conentration which is everywhere within definite limits of the mean concentration. Additionally, a certain amount of the fuel is vap~rized in the fuel preparation zone.
Fuel combustion occurs at a point downstream from the fueL
preparatlon zonc. The substantially unlform fuel concen-tration achieved in the fuel preparation zone results in a uniform reaction temperature ~hich may be li.mited to .....
3 49,~85 approximately 2000F ~o 30C0F. Due to the uniormity and thoroughness of combustion, the pre mixing, prevaporizing combustor produces lower levels of NO~ and CO than does a conventional combustor uslng the same amount o fuel.
One problem with premixing, prevaporizlng com~
bustors is the destructive potential for flashback, or sudden propagation of flame from the polnt of combustion back into the fuel preparation zone. If permitted to continue uncorrected, the presence of flame in the fuel 10 preparation zone will damage the con~ustor to the e~tent that the turbine must be shut down and the combustor re-paired or replaced. This phenomenon has been classically define~ to involve the competing relationship between the flow velocity and the flame velocity of the combustible 15 ga~es. Because the flame velocity is ordinarily charac-teristic o the fuel used, the flow velocity is more readily within the control of the designer. For further elaboration of the classical approach to flashback see 3.
Lewis, G. von Elbe, Combustlo_, Flames ~nd Explosions of 20 Gases, Ac~demic Press, New York (1961).
Elame stability in a combustor was later 52mi-quantified by S. L. Plse and A. M. Mellor. See "Review Of 5Flashback Reported In Prevaporizing/Premixing Combustors,"
32 Combustion and Flame 193-203 (1978). The formuia 25 sug~ested by Plee and Mellor for stability i5 as follows:
1/9 = m/(P AD~ exp (T/C)) where:
.
m - mass flow rate of combustible gases in the fuel preparation zone P = absolute pressure of the fuel pxepaxation zone A = cross-sectionaL area of the fuel preparation zone D - cross-sectional diameter of the fuel preparation 7one
One problem with premixing, prevaporizlng com~
bustors is the destructive potential for flashback, or sudden propagation of flame from the polnt of combustion back into the fuel preparation zone. If permitted to continue uncorrected, the presence of flame in the fuel 10 preparation zone will damage the con~ustor to the e~tent that the turbine must be shut down and the combustor re-paired or replaced. This phenomenon has been classically define~ to involve the competing relationship between the flow velocity and the flame velocity of the combustible 15 ga~es. Because the flame velocity is ordinarily charac-teristic o the fuel used, the flow velocity is more readily within the control of the designer. For further elaboration of the classical approach to flashback see 3.
Lewis, G. von Elbe, Combustlo_, Flames ~nd Explosions of 20 Gases, Ac~demic Press, New York (1961).
Elame stability in a combustor was later 52mi-quantified by S. L. Plse and A. M. Mellor. See "Review Of 5Flashback Reported In Prevaporizing/Premixing Combustors,"
32 Combustion and Flame 193-203 (1978). The formuia 25 sug~ested by Plee and Mellor for stability i5 as follows:
1/9 = m/(P AD~ exp (T/C)) where:
.
m - mass flow rate of combustible gases in the fuel preparation zone P = absolute pressure of the fuel pxepaxation zone A = cross-sectionaL area of the fuel preparation zone D - cross-sectional diameter of the fuel preparation 7one
4 ~9,~5 T = absolute temperature of the fuel preparation zone a, b, ~ c = constants, greater than zero It was reported that the value of 1/~ for a fuel preparation zone is representative of the stability of the combustion flame. With larger values of 1/3 the fuel preparation zone is less prone to flashback. From the equation it can be determined that flame stability is promoted by a reduction in the cross-sectional dimensions of the fuel preparation zone.
Reduction of the cr.oss-sectional ar~a, however, places severe restrictions on the designer by limiting fuel nozzle selection to smaller nozzles. In general, smaller noz~les suffer from more limited availability, greater expense, an~ a greater pressure drop across the nozzle as compared to larger nozzles. Pressure loss within the combustor is to ba minimized so that the work-ing efficiency of the combustion turbine is maintained.
The danger of flashback becomes especially acute when fuel concentration in the fuel preparaticn zone is high, as in the case of a fueL-rich fuel preparation.
Operating a combu~tor in a fuel-rich configuration can reduce NOX ~missions by effectively depleting the oxygen which would ordinarily be avallable to combine with nitro-gen to form NOX. Without specific safeguards directed at preventing fiashbac~, use of a fuel-rich fuel preparation zone would not be possible in a premixing, prevaporizing combustor.
Thus, the known prior art does not appear to meet the need for preventing flashbac~ in a premi.~ing, prevaporizing combustor without reducing the cross-sectional area of the fuel preparation zone.
SUMMA~Y OF THE INVENTION
Accordingly, a combus~ion turbine combustor com-prises an enclo~ure or basket having apertures for permit-~ing the fl.ow of compressor discharge gases lnto the en~closure, fuel injection means wittl1n the enclosure down-,~
4g,685 stream of one or more of the apertures, a fuel preparationzone downstream of the fuel injection means, a structure within the fueL preparation zone for mlxing and vaporizing the fuel to obtain a homogeneous fuel mixture, means within the fuel preparation zone for accelerating the flow of the mixture through a co~ustion zorle, and a cor~ustion zone for supporting co~bust:ion of the fuel mixture The mi~ing structure i5 arranged to provide acceleration of the fuel mixture through the combustion zone to permit use of a high fuel concentration within the fuel preparation zone and yet diminish the danger of flashback. The means of combustion may be by flam~ or by catalyst; in both ca es, the increased flow veloclty through the combustion zone by virtue of the arrangement of the mixing structure serves to prevent 1ashback.
BRIEF_DESCRIPTION OF THE DRAWINGS
Figura 1 schematically shows a catalytic combus-tor arranged to operate a gas turbine in accordance with the principles of the invention;
Eigure 2 shows an elevational view of a cataly-tic combustor;
Figure 3 shows a fuel preparation zone for a combustor arranged in accordance with the principles of the invention;
Fi~ure 4 shows a static mixer of Figure 3 in section;
Figure 5 shows a side view of an alternative internal structure for the static mixer shown in Figure 3.
DESCRIPTION OF THE PREFERRED EMBODI~ENT
Mors par~icularly, there is shown in Figure 1 a generalized schematic representation of a combustion tur-bine combustor and combu~tor control system. A tu~bine or generaLly cylindrical catalytic combustor 10 i5 combined with a pluralit-~ o~ like combustors (not shown) to su~ply hot ~otlve gas to the inlet of a turbine (~ot shown) as indicated by reference charact-r 12. The combustor 12 includes a catalytic uni~ 1~ which suppo~ts catal~tic com-s~
~ gg,685 bustion (oxidation) of fuelwair mixture 10wing through the combustor 10.
The combustor 10 includes a zone 11 into which fueL, such as oil, is injected by nozzle means 16 from a S uel valve 17, where fuel-air mlxing occurs in preparation for entry into the cataly-tic unit 14. Typically, the fuel-air mix temperature (for example 800F) required for catalytic reaction is higher than the temperature (for sxample 700Fj of the compressor discharge air supplied to the combu~tors from the enclosed space outside the combus-tor shells. Th~ deficiency in air supply temperature in typical cases is highest during startup and lower load operation.
A primary combustion zone 18 is accordingly provid~d up-~tream from the fuel preparation ~one 11 within the combustor 10. No7zle means 20 are provided for in-jecting fuel from a primary fuel valve ~2 into the primary combustion zone 18 where conventional flame combustion is supported by primary air entering the ~-one 18 from the space within the turbine casing throu~h openings in the combustor wall.
As a result, a hot gas flow is supplied to the îuel preparation zone 11 where it can be mixed with the fuel and air mixture to provide a heated fuel mixture at a sufficiently high temperature to enable proper catalytic unit operation. In this arrangement, the fuel inject2d by the nozzle means 16 for combustion in the catalytic unit is a secondary fuel flow. The secondary fuel flow i5 mixed with secondary air and primary combustion products, ~hich supply the preheating needed to raise the tempera-ture of the mixture to the level needed for entry into the catalytic unit.
It should be notsd that a combustor structured according to the principles of the invention ls not l.imit-ed to the catalytic struc.ure described above. Othercombustors structured according to the principles of the invention include catalytic combustors having no primary s~
7 ~9,685 combustion zone or preheating the gas flow and non-catalytic combustors. A non-cataLytic combustor (not shown) structured consistent with the principles of the invention compris2s nozzle means injecting fuel into a fuel prepa~ation zone for fuel-air mixin~. Combustion of the ~uel-air mixture occurs at: a flameholder or in an open section in a co~bustion zone downstream OI the fuel prep aration zone/ producing a hot gas flow which is supplied to the turbine inlet. The description hereinafter is directed expressly to a catalytic combustor but applies egually well to a non-catalytic combustor.
In Figure 2 there is shown a structurally de-tailed catalytic combustion systam 30 embodying the prin-ciples described for the combustor 10 of Figure 1. Thus, the combustion system 30 generates hot combustion products ~hich pass through stator vanes 31 to drive turbine blades (not shown). A plurality of combustion systems 30 are disposed about the rotor axis within a turbine casing 32 t~ supply the total hot gas flow needed to drive the turbine.
In accordance wi~h the principles of the inven-tlon, the combus~or 30 includes a combustor enclosure or basket 40, a catalytic unit 36 and a transition duct 38 which directs tha hot gas to the annular space through which it passes to be directed against the turbine blades.
Tho combustor 30 further comprises a fuel preparation zone internal to the combustor basket AO at reference char~c^
ter 34.
A fuel preparation zone of the combustor 30 of Eigure 2 is shown in section in Figure 3. The fuel pre-paration zone comprises one or more nozzle means 42 for injecting fuel into the fuel preparatlon zone, a prelimi-nary mixing area 44, and a static mixer 46. Initial fuel-air mixing occurs in the area 44 when fuel is sprayed into a flow of compressor discharge air. Complete mixing of the fuel~-air mlx~ure to obtain a uni orm ~oncentration of the fuel throughout the mixture occurs as he mix~ure S~
~ 49,~5 flows thro~gh the static mixing s~ructure ~6. The static mixing structure 46 is arrang~d to provide efficient fuel mixing while minimizing lcss o pressure across the mixing str-ucture 46.
The structure of the static mixlng structure 46 is utili7ed to provide to the designer a means for con-trolling the flo~ velocity of the gaseous mixture, supple-me~tlng the control inherent in the choice of the cross-sectional dimension of the combustor. The significance of this control element is de~monstrated by the following equation for flow velocity:
.
V ~ m/dKA
where:
V = flow velocity of the combustible gases in the fuel preparation zone m = mass flow rate of combusti~le gases d = density of the combustible gases in the fuel preparation zone K = void fraction of the fuel preparation zone 20~ = cross~sectional area of the fuel preparation ~one The void fracti~n (K) equals the ratio of un-obstructed cross-sectional area to total cross-sectional are of the fuel preparation zone. Thus, the void frac~
25 tion for an unobstructed fuel preparatlon zone equals 1.O.
.~s can be seen from the a~ove equation, the flow velocity oî the gaseous mixture may be increased by decreasing the void fraction of the fuel preparation zone. The static mixing structure 46 provides a convenient means for de-creasing the void fraction of the fuel preparation zone and thereby increasing the flow velocity of the gaseous mixture, without decreasing the cross-sectional dimensions of the fuel preparation zone. Use o,^ the static mixing structure a6 in this way permits a high fuel concentration ag, 685 (fueL-rich) fuel preparation zone without constraining the col~bustor dimensions available to the designer.
Flgure 4 shows a cross-section of the static mixing structure 46 disclosed in Figure 3. The lnternal
Reduction of the cr.oss-sectional ar~a, however, places severe restrictions on the designer by limiting fuel nozzle selection to smaller nozzles. In general, smaller noz~les suffer from more limited availability, greater expense, an~ a greater pressure drop across the nozzle as compared to larger nozzles. Pressure loss within the combustor is to ba minimized so that the work-ing efficiency of the combustion turbine is maintained.
The danger of flashback becomes especially acute when fuel concentration in the fuel preparaticn zone is high, as in the case of a fueL-rich fuel preparation.
Operating a combu~tor in a fuel-rich configuration can reduce NOX ~missions by effectively depleting the oxygen which would ordinarily be avallable to combine with nitro-gen to form NOX. Without specific safeguards directed at preventing fiashbac~, use of a fuel-rich fuel preparation zone would not be possible in a premixing, prevaporizing combustor.
Thus, the known prior art does not appear to meet the need for preventing flashbac~ in a premi.~ing, prevaporizing combustor without reducing the cross-sectional area of the fuel preparation zone.
SUMMA~Y OF THE INVENTION
Accordingly, a combus~ion turbine combustor com-prises an enclo~ure or basket having apertures for permit-~ing the fl.ow of compressor discharge gases lnto the en~closure, fuel injection means wittl1n the enclosure down-,~
4g,685 stream of one or more of the apertures, a fuel preparationzone downstream of the fuel injection means, a structure within the fueL preparation zone for mlxing and vaporizing the fuel to obtain a homogeneous fuel mixture, means within the fuel preparation zone for accelerating the flow of the mixture through a co~ustion zorle, and a cor~ustion zone for supporting co~bust:ion of the fuel mixture The mi~ing structure i5 arranged to provide acceleration of the fuel mixture through the combustion zone to permit use of a high fuel concentration within the fuel preparation zone and yet diminish the danger of flashback. The means of combustion may be by flam~ or by catalyst; in both ca es, the increased flow veloclty through the combustion zone by virtue of the arrangement of the mixing structure serves to prevent 1ashback.
BRIEF_DESCRIPTION OF THE DRAWINGS
Figura 1 schematically shows a catalytic combus-tor arranged to operate a gas turbine in accordance with the principles of the invention;
Eigure 2 shows an elevational view of a cataly-tic combustor;
Figure 3 shows a fuel preparation zone for a combustor arranged in accordance with the principles of the invention;
Fi~ure 4 shows a static mixer of Figure 3 in section;
Figure 5 shows a side view of an alternative internal structure for the static mixer shown in Figure 3.
DESCRIPTION OF THE PREFERRED EMBODI~ENT
Mors par~icularly, there is shown in Figure 1 a generalized schematic representation of a combustion tur-bine combustor and combu~tor control system. A tu~bine or generaLly cylindrical catalytic combustor 10 i5 combined with a pluralit-~ o~ like combustors (not shown) to su~ply hot ~otlve gas to the inlet of a turbine (~ot shown) as indicated by reference charact-r 12. The combustor 12 includes a catalytic uni~ 1~ which suppo~ts catal~tic com-s~
~ gg,685 bustion (oxidation) of fuelwair mixture 10wing through the combustor 10.
The combustor 10 includes a zone 11 into which fueL, such as oil, is injected by nozzle means 16 from a S uel valve 17, where fuel-air mlxing occurs in preparation for entry into the cataly-tic unit 14. Typically, the fuel-air mix temperature (for example 800F) required for catalytic reaction is higher than the temperature (for sxample 700Fj of the compressor discharge air supplied to the combu~tors from the enclosed space outside the combus-tor shells. Th~ deficiency in air supply temperature in typical cases is highest during startup and lower load operation.
A primary combustion zone 18 is accordingly provid~d up-~tream from the fuel preparation ~one 11 within the combustor 10. No7zle means 20 are provided for in-jecting fuel from a primary fuel valve ~2 into the primary combustion zone 18 where conventional flame combustion is supported by primary air entering the ~-one 18 from the space within the turbine casing throu~h openings in the combustor wall.
As a result, a hot gas flow is supplied to the îuel preparation zone 11 where it can be mixed with the fuel and air mixture to provide a heated fuel mixture at a sufficiently high temperature to enable proper catalytic unit operation. In this arrangement, the fuel inject2d by the nozzle means 16 for combustion in the catalytic unit is a secondary fuel flow. The secondary fuel flow i5 mixed with secondary air and primary combustion products, ~hich supply the preheating needed to raise the tempera-ture of the mixture to the level needed for entry into the catalytic unit.
It should be notsd that a combustor structured according to the principles of the invention ls not l.imit-ed to the catalytic struc.ure described above. Othercombustors structured according to the principles of the invention include catalytic combustors having no primary s~
7 ~9,685 combustion zone or preheating the gas flow and non-catalytic combustors. A non-cataLytic combustor (not shown) structured consistent with the principles of the invention compris2s nozzle means injecting fuel into a fuel prepa~ation zone for fuel-air mixin~. Combustion of the ~uel-air mixture occurs at: a flameholder or in an open section in a co~bustion zone downstream OI the fuel prep aration zone/ producing a hot gas flow which is supplied to the turbine inlet. The description hereinafter is directed expressly to a catalytic combustor but applies egually well to a non-catalytic combustor.
In Figure 2 there is shown a structurally de-tailed catalytic combustion systam 30 embodying the prin-ciples described for the combustor 10 of Figure 1. Thus, the combustion system 30 generates hot combustion products ~hich pass through stator vanes 31 to drive turbine blades (not shown). A plurality of combustion systems 30 are disposed about the rotor axis within a turbine casing 32 t~ supply the total hot gas flow needed to drive the turbine.
In accordance wi~h the principles of the inven-tlon, the combus~or 30 includes a combustor enclosure or basket 40, a catalytic unit 36 and a transition duct 38 which directs tha hot gas to the annular space through which it passes to be directed against the turbine blades.
Tho combustor 30 further comprises a fuel preparation zone internal to the combustor basket AO at reference char~c^
ter 34.
A fuel preparation zone of the combustor 30 of Eigure 2 is shown in section in Figure 3. The fuel pre-paration zone comprises one or more nozzle means 42 for injecting fuel into the fuel preparatlon zone, a prelimi-nary mixing area 44, and a static mixer 46. Initial fuel-air mixing occurs in the area 44 when fuel is sprayed into a flow of compressor discharge air. Complete mixing of the fuel~-air mlx~ure to obtain a uni orm ~oncentration of the fuel throughout the mixture occurs as he mix~ure S~
~ 49,~5 flows thro~gh the static mixing s~ructure ~6. The static mixing structure 46 is arrang~d to provide efficient fuel mixing while minimizing lcss o pressure across the mixing str-ucture 46.
The structure of the static mixlng structure 46 is utili7ed to provide to the designer a means for con-trolling the flo~ velocity of the gaseous mixture, supple-me~tlng the control inherent in the choice of the cross-sectional dimension of the combustor. The significance of this control element is de~monstrated by the following equation for flow velocity:
.
V ~ m/dKA
where:
V = flow velocity of the combustible gases in the fuel preparation zone m = mass flow rate of combusti~le gases d = density of the combustible gases in the fuel preparation zone K = void fraction of the fuel preparation zone 20~ = cross~sectional area of the fuel preparation ~one The void fracti~n (K) equals the ratio of un-obstructed cross-sectional area to total cross-sectional are of the fuel preparation zone. Thus, the void frac~
25 tion for an unobstructed fuel preparatlon zone equals 1.O.
.~s can be seen from the a~ove equation, the flow velocity oî the gaseous mixture may be increased by decreasing the void fraction of the fuel preparation zone. The static mixing structure 46 provides a convenient means for de-creasing the void fraction of the fuel preparation zone and thereby increasing the flow velocity of the gaseous mixture, without decreasing the cross-sectional dimensions of the fuel preparation zone. Use o,^ the static mixing structure a6 in this way permits a high fuel concentration ag, 685 (fueL-rich) fuel preparation zone without constraining the col~bustor dimensions available to the designer.
Flgure 4 shows a cross-section of the static mixing structure 46 disclosed in Figure 3. The lnternal
5 arrangement of the static mixing struc~ure '16 comprises a plurality of layers of corrugated material, such as metal alloy, arranged to define a plurality of passageways 50.
The layers of corrugated material may be arranged in sev-exal continuous sections (not shown), so that when the sections are disposed end-to-end to form a plurality of continuous passageways through the several sections, tho passageways of any two adjacent sections form angles of 90 or more with respect to one another. The thickness of the corrugated material may be chosen according to the above e~quation to provide the desired fiow velocity.
Figure 5 shows an elevation of an alternative arrangement for the static mixing structure g6 of Figure 3. The structure disclosed is essentialLy a flat bar twisted 360~ to create a spiral defining dual passageways.
This structure alone may be utilized or, alternatively, it may be coupled with a second 360 spiral in the reverse direction to increase the degree o mixedness within the static mixing structure 46. In both cases, the thic~ness of the metal bar is chosen to provide an appropriate void fraction as set forth in the equation above.
Hence, a premixing, prevapori7ing combustor m~y be structured according to the principles of the invention to minimize the chance of flashbac~ and thereby enable the combustor to operate in a fuel-rich configu~ation. By appropriate design of the static mixing s~ruc_ure, îlo~-velocity OI the fuel-air mixtura through the combustion zone is increased, decreasing the risk of flashback ~ith-out altering the cross-sectional dimensions of the fuel preparation zone.
The layers of corrugated material may be arranged in sev-exal continuous sections (not shown), so that when the sections are disposed end-to-end to form a plurality of continuous passageways through the several sections, tho passageways of any two adjacent sections form angles of 90 or more with respect to one another. The thickness of the corrugated material may be chosen according to the above e~quation to provide the desired fiow velocity.
Figure 5 shows an elevation of an alternative arrangement for the static mixing structure g6 of Figure 3. The structure disclosed is essentialLy a flat bar twisted 360~ to create a spiral defining dual passageways.
This structure alone may be utilized or, alternatively, it may be coupled with a second 360 spiral in the reverse direction to increase the degree o mixedness within the static mixing structure 46. In both cases, the thic~ness of the metal bar is chosen to provide an appropriate void fraction as set forth in the equation above.
Hence, a premixing, prevapori7ing combustor m~y be structured according to the principles of the invention to minimize the chance of flashbac~ and thereby enable the combustor to operate in a fuel-rich configu~ation. By appropriate design of the static mixing s~ruc_ure, îlo~-velocity OI the fuel-air mixtura through the combustion zone is increased, decreasing the risk of flashback ~ith-out altering the cross-sectional dimensions of the fuel preparation zone.
Claims (10)
1. In a combustion turbine system, a combustor for heating compressor discharge gases to drive a turbine, said combustor comprising:
an enclosure for containing the combustion reac-tion, said enclosure being generally cylindrical and having apertures therethrough toward an upstream end to permit influx of compressor discharge gases which flow into said enclosure and exit through an open downstream end of said enclosure into a transition duct which leads to a turbine inlet;
means for injecting fuel into the flow of gases within said enclosure, said fuel injecting means positioned within said enclosure downstream of at least one of the apertures in said enclosure;
a fuel preparation zone located downstream of said fuel injecting means, said zone having therein means for mixing and vaporizing the fuel to obtain a homogeneous gaseous fuel mixture upstream of a combustion zone;
means within said fuel preparation zone for increasing the flow velocity of the fuel mixture through the combustion zone; and a combustion zone located downstream of said fuel preparation zone, said combustion zone having therein means for initiating and supporting combustion of the fuel mixture, the temperature of gases flowing into the transi-tion duct being thereby increased.
an enclosure for containing the combustion reac-tion, said enclosure being generally cylindrical and having apertures therethrough toward an upstream end to permit influx of compressor discharge gases which flow into said enclosure and exit through an open downstream end of said enclosure into a transition duct which leads to a turbine inlet;
means for injecting fuel into the flow of gases within said enclosure, said fuel injecting means positioned within said enclosure downstream of at least one of the apertures in said enclosure;
a fuel preparation zone located downstream of said fuel injecting means, said zone having therein means for mixing and vaporizing the fuel to obtain a homogeneous gaseous fuel mixture upstream of a combustion zone;
means within said fuel preparation zone for increasing the flow velocity of the fuel mixture through the combustion zone; and a combustion zone located downstream of said fuel preparation zone, said combustion zone having therein means for initiating and supporting combustion of the fuel mixture, the temperature of gases flowing into the transi-tion duct being thereby increased.
2. A combustor according to claim 1 wherein said mixing means comprises a static mixing structure, said structure having a plurality of angled passageways arranged to induce flow characteristics in the fuel mix-ture flowing therethrough to mix and vaporize the fuel without substantial loss of pressure.
3. A combustor according to claim 2 wherein said means for increasing flow velocity comprises the static mixing structure having a cross-sectional area which substantially decreases the unobstructed cross-sectional area of said combustor so as to increase the flow velocity in said combustion zone downstream to a predetermined flow velocity.
4. A combustor according to claim 3 wherein said means for supporting combustion comprises a flame-holder in said combustion zone downstream of the static mixing structure.
5. A combustor according to claim 3 wherein said means for supporting combustion comprises a catalytic combustion element in said combustion zone downstream of the static mixing structure.
6. A combustor according to claims 4 or 5 wherein the static mixing structure comprises a plurality of horizontal sections, each of said sections comprising a plurality of corrugated vertically stacked layers, the stacked layers having a thickness chosen to produce the desired flow acceleration and adjacent layers being offset to define horizontal passageways between the layers, the sections aligned end-to-end to form the continuous angled passageways through the combination of sections, the passageways of each section oriented at an angle with respect to adjacent sections, so that the fuel and gases entering the static mixing structure flow through the angled passageways and are thereby mixed and accelerated to produce the flow of homogeneous fuel mixture.
7. A combustor according to claims 4 wherein the static mixing structure comprises a spiral structure formed of a metallic bar, having a thickness chosen to produce the desired flow acceleration, with one end of the bar rotated 360° relative to the other end to define dual passageways.
8. A combustor according to claim 7 wherein the static mixing structure comprises a plurality of spiral structures arranged end-to-end to define dual continuous passageways, adjacent spiral structures spiralling in opposing directions.
9. A combustor according to claim 5 wherein the static mixing structure comprises a spiral structure formed of a metallic bar, having a thickness chosen to produce the desired flow acceleration, with one end of the bar rotated 360° relative to the other end to define dual passageways.
10. A combustor according to claim 9 wherein the static mixing structure comprises a plurality of spiral structures arranged end-to-end to define dual continuous passageways, adjacent spiral structures spiralling in opposing directions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US31704481A | 1981-11-02 | 1981-11-02 | |
| US317,044 | 1994-10-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1190051A true CA1190051A (en) | 1985-07-09 |
Family
ID=23231862
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000405430A Expired CA1190051A (en) | 1981-11-02 | 1982-06-17 | Combustion turbine combustor having an improved fuel- rich fuel preparation zone |
Country Status (7)
| Country | Link |
|---|---|
| JP (2) | JPS5878015A (en) |
| BE (1) | BE893710A (en) |
| BR (1) | BR8203784A (en) |
| CA (1) | CA1190051A (en) |
| GB (1) | GB2108651B (en) |
| IT (1) | IT1152245B (en) |
| MX (1) | MX156338A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2249828A (en) * | 1990-11-13 | 1992-05-20 | Rolls Royce Plc | Fuel vapouriser |
| WO1997040316A1 (en) * | 1996-04-19 | 1997-10-30 | Westinghouse Electric Corporation | Premixed combustor with flashback arrestors |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1070127A (en) * | 1974-11-04 | 1980-01-22 | Serafino M. Decorso | Catalytic combustor |
-
1982
- 1982-06-16 IT IT21875/82A patent/IT1152245B/en active
- 1982-06-17 CA CA000405430A patent/CA1190051A/en not_active Expired
- 1982-06-29 BR BR8203784A patent/BR8203784A/en unknown
- 1982-06-30 BE BE0/208499A patent/BE893710A/en not_active IP Right Cessation
- 1982-07-02 MX MX193422A patent/MX156338A/en unknown
- 1982-07-02 JP JP57114133A patent/JPS5878015A/en active Pending
- 1982-07-02 GB GB08219211A patent/GB2108651B/en not_active Expired
-
1986
- 1986-01-21 JP JP1986005949U patent/JPH0335986Y2/ja not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5878015A (en) | 1983-05-11 |
| BR8203784A (en) | 1983-06-21 |
| GB2108651A (en) | 1983-05-18 |
| JPH0335986Y2 (en) | 1991-07-30 |
| MX156338A (en) | 1988-08-10 |
| IT8221875A0 (en) | 1982-06-16 |
| JPS61135171U (en) | 1986-08-22 |
| GB2108651B (en) | 1985-06-12 |
| IT1152245B (en) | 1986-12-31 |
| BE893710A (en) | 1982-12-30 |
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