Note: Within nine months of the publication of the mention of the grant of the European patent in the European PatentBulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with theImplementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has beenpaid. (Art. 99(1) European Patent Convention).

Printed by Jouve, 75001 PARIS (FR)

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(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention of the grant of the patent: 23.07.2014 Bulletin 2014/30

(21) Application number: 02253028.1

(22) Date of filing: 29.04.2002

(51) Int Cl.:F23R 3/04 (2006.01) F23R 3/34 (2006.01)

F23R 3/28 (2006.01) F23C 6/04 (2006.01)

(54) A tubular combustion chamber

Rohrbrennkammer

Chambre de combustion tubulaire

(84) Designated Contracting States: CH DE FR GB LI SE

(30) Priority: 15.05.2001 GB 0111788

(43) Date of publication of application: 27.11.2002 Bulletin 2002/48

(73) Proprietors: • ROLLS-ROYCE PLC

London, SW1E 6AT (GB)• Rolls-Royce Canada Limited

Lachine,Quebec H9P 1A3 (CA)

(72) Inventors: • Freeman, Christopher

Farnsfield,Nottingham NG22 8JN (GB)

• Day, Ivor JohnComberton,Cambridge CB3 7EE (GB)

• Scarinci, ThomasMont Royal,Quebec H3P 2J8 (CA)

(74) Representative: Barcock, Ruth Anita et alRolls-Royce plc Intellectual Property Department P.O. Box 31Derby DE24 8BJ (GB)

(56) References cited: EP-A- 0 863 369 EP-A- 1 108 957US-A- 2 560 074 US-A- 4 412 414US-A- 5 235 814 US-A- 5 475 979US-A- 6 016 658 US-A- 6 164 055

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Description

[0001] The present invention relates generally to acombustion chamber, particularly to a gas turbine enginecombustion chamber.[0002] In order to meet the emission level require-ments, for industrial low emission gas turbine engines,staged combustion is required in order to minimise thequantity of the oxide of nitrogen (NOx) produced. Cur-rently the emission level requirement is for less than 25volumetric parts per million of NOx for an industrial gasturbine exhaust. The fundamental way to reduce emis-sions of nitrogen oxides is to reduce the combustion re-action temperature, and this requires premixing of thefuel and a large proportion, preferably all, of the combus-tion air before combustion occurs. The oxides of nitrogen(NOx) are commonly reduced by a method, which usestwo stages of fuel injection. Our UK patent no.GB1489339 discloses two stages of fuel injection. OurInternational patent application no. WO92/07221 disclos-es two and three stages of fuel injection. In staged com-bustion, all the stages of combustion seek to provide leancombustion and hence the low combustion temperaturesrequired to minimise NOx. The term lean combustionmeans combustion of fuel in air where the fuel to air ratiois low, i.e. less than the stoichiometric ratio. In order toachieve the required low emissions of NOx and CO it isessential to mix the fuel and air uniformly.[0003] The industrial gas turbine engine disclosed inour International patent application no. WO92/0722 usesa plurality of tubular combustion chambers, whose axesare arranged in generally radial directions. The inlets ofthe tubular combustion chambers are at their radially out-er ends, and transition ducts connect the outlets of thetubular combustion chambers with a row of nozzle guidevanes to discharge the hot gases axially into the turbinesections of the gas turbine engine. Each of the tubularcombustion chambers has two coaxial radial flow swirl-ers, which supply a mixture of fuel and air into a primarycombustion zone. An annular secondary fuel and air mix-ing duct surrounds the primary combustion zone and sup-plies a mixture of fuel and air into a secondary combustionzone.[0004] One problem associated with gas turbine en-gines is caused by pressure fluctuations in the air, or gas,flow through the gas turbine engine. Pressure fluctua-tions in the air, or gas, flow through the gas turbine enginemay lead to severe damage, or failure, of components ifthe frequency of the pressure fluctuations coincides withthe natural frequency of a vibration mode of one or moreof the components. These pressure fluctuations may beamplified by the combustion process and under adverseconditions a resonant frequency may achieve sufficientamplitude to cause severe damage to the combustionchamber and the gas turbine engine. Alternatively theamplitude of the pressure fluctuations may be sufficientlylarge such as to induce damage to the combustion cham-ber and the gas turbine engine in their own right.

[0005] It has been found that gas turbine engines,which have lean combustion, are particularly susceptibleto this problem. Furthermore it has been found that asgas turbine engines which have lean combustion reduceemissions to lower levels by achieving more uniform mix-ing of the fuel and the air, the amplitude of the resonantfrequency becomes greater. It is believed that the ampli-fication of the pressure fluctuations in the combustionchamber occurs because the heat released by the burn-ing of the fuel occurs at a position in the combustionchamber, which corresponds, to an antinode, or pressurepeak, in the pressure fluctuations.[0006] Our European patent application No.00311040.0 filed 11 December 2000, which claims pri-ority from UK patent application 9929601.4 filed 16 De-cember 1999 discloses a combustion chamber arrangedto reduce this problem. The combustion chamber has atleast one fuel and air mixing duct for supplying a fuel andair mixture to a combustion zone in the combustion cham-ber. Fuel injection means is arranged to supply fuel intothe at least one fuel and air mixing duct. Air injectionmeans is arranged to supply air into the at least one fueland air mixing duct. The air injection means comprisesa plurality of air injectors spaced apart in the direction offlow through the at least one fuel and air mixing duct toreduce the magnitude of the fluctuations in the fuel to airratio of the fuel and air mixture supplied into the at leastone combustion zone.[0007] US6016658 discloses a combustion system fora gas turbine engine.[0008] However, although the fuel to air ratio fluctua-tions have been reduced there is a risk of auto ignitionof the fuel in the fuel and air mixing duct in the wakesfrom the air injectors due to the possibility of excessivelylong residence times in the fuel and air mixing duct. Therisk of excessively long residence time is a function ofthe gas turbine engine pressure ratio. The higher thepressure ratio, the higher the risk of autoignition.[0009] Accordingly the present invention seeks to pro-vide a combustion chamber which reduces or minimisesthe above-mentioned problem.[0010] Accordingly the present invention provides acombustion chamber according to claim 1.[0011] The present invention also provides a combus-tion chamber according to claim 2.[0012] Preferably the combustion chamber accordingto claim 2 comprises a primary combustion zone and asecondary combustion zone downstream of the primarycombustion zone.[0013] Preferably the combustion chamber comprisesa primary combustion zone, a secondary combustionzone downstream of the primary combustion zone anda tertiary combustion zone downstream of the secondarycombustion zone.[0014] The at least one fuel and air mixing duct maysupply fuel and air into the primary combustion zone. Theat least one fuel and air mixing duct may supply fuel andair into the secondary combustion zone. The at least one

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fuel and air mixing duct may supply fuel and air into thetertiary combustion zone.[0015] Preferably the fuel injector means is arrangedbetween the upstream end and the downstream end ofthe at least one fuel and air mixing duct, a portion of theair injector means are arranged upstream of the fuel in-jector means and a portion of the air injector means arearranged downstream of the fuel injector means.[0016] Preferably each air injector means at the down-stream end of the fuel and air mixing duct is arranged tosupply more air into the fuel and air mixing duct than saidair injector means at the upstream end of the fuel and airmixing duct.[0017] Preferably each air injector means at a first po-sition in the direction of flow through the fuel and air mix-ing duct is arranged to supply more air into the fuel andair mixing duct than said air injector means upstream ofthe first position in the fuel and air mixing duct.[0018] Preferably each air injector means at the firstposition in the fuel and air mixing duct is arranged tosupply less air into the fuel and air mixing duct than saidair injector means downstream of the first position in thefuel and air mixing duct.[0019] Preferably the volume of the fuel and air mixingduct being arranged such that the average travel timefrom the fuel injection means to the downstream end ofthe fuel and air mixing duct is greater than the time periodof the fluctuation.[0020] Preferably the volume of the fuel and air mixingduct being arranged such that the length of the fuel andair mixing duct multiplied by the frequency of the fluctu-ations divided by the velocity of the fuel and air leavingthe downstream end of the fuel and air mixing duct is atleast one.[0021] Preferably the volume of the fuel and air mixingduct being arranged such that the length of the fuel andair mixing duct multiplied by the frequency of the fluctu-ations divided by the velocity of the fuel and air leavingthe downstream end of the fuel and air mixing duct is atleast two.[0022] Preferably the plurality of air injectors extend inthe direction of flow through the at least one fuel and airmixing duct over a length equal to half the wavelength ofthe fluctuations of the air supplied to the at least one fueland air mixing duct.[0023] Preferably the length of an air injector in thedirection of flow through the at least one fuel and air mix-ing duct multiplied by the frequency of the fluctuationsdivided by the velocity of the fuel and air inside the atleast one mixing duct is at least one.[0024] Preferably the length of an air injector in thedirection of flow through the at least one fuel and air mix-ing duct multiplied by the frequency of the fluctuationsdivided by the average velocity of the fuel and air insidethe at least one mixing duct is at least two.[0025] Preferably the at least one fuel and air mixingduct comprises a swirler. Preferably the swirler is a radialflow swirler.

[0026] The present invention will be more fully de-scribed by way of example with reference to the accom-panying drawings, in which:-

Figure 1 is a view of a gas turbine engine having acombustion chamber according to the present inven-tion.Figure 2 is an enlarged longitudinal cross-sectionalview through the combustion chamber shown in fig-ure 1.Figure 3 is an enlarged cross-sectional view of partof the primary fuel and air mixing duct shown in figure2.Figure 4 is an enlarged cross-sectional view of partof the secondary fuel and air mixing duct shown infigure 2.Figure 5 is a cross-sectional view of an alternativefuel and air mixing duct not forming part of the inven-tion.Figure 6 is a cross-sectional view in the direction ofarrows W-W in figure 5.Figure 7 is a cross-sectional view in the direction ofarrows X-X in figure 5.Figure 8 is a cross-sectional view of another alter-native fuel and air mixing duct not forming part of theinvention.Figure 9 is a cross-sectional view in the direction ofarrows Y-Y in figure 8.Figure 10 is a cross-sectional view in the directionof arrows Z-Z in figure 8.Figure 11 is a graph comparing the fuel to air ratiofluctuation with radial distance in a radial flow fueland air mixing duct according to the present inven-tion and a radial flow fuel and air mixing duct accord-ing to the prior art.Figure 12 is a graph of the fuel to air ratio of a fueland air mixing duct according to the present inven-tion divided by the fuel to air ratio of a fuel and airmixing duct according to the prior art against the fre-quency of fluctuation multiplied by the length of thefuel and air mixing duct divided by the velocity of thefuel and air mixture leaving the fuel and air mixingduct.Figure 13 is a cross-sectional view of an alternativefuel and air mixing duct.Figure 14 is cross-sectional view in the direction ofarrows T-T in figure 13.Figure 15 is a cross-sectional view of a further fueland air mixing duct.Figure 16 is a graph of the fuel to air ratio of fuel andair mixing ducts according to the present inventionagainst the frequency of the fluctuation multiplied bythe length of the fuel and air mixing duct divided bythe velocity of the fuel and air mixture leaving thefuel and air mixing duct.

[0027] An industrial gas turbine engine 10, shown infigure 1, comprises in axial flow series an inlet 12, a com-

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pressor section 14, a combustion chamber assembly 16,a turbine section 18, a power turbine section 20 and anexhaust 22. The turbine section 18 is arranged to drivethe compressor section 14 via one or more shafts (notshown). The power turbine section 20 is arranged to drivean electrical generator 26 via a shaft 24. The operationof the gas turbine engine 10 is quite conventional, andwill not be discussed further. Alternatively, the turbinesection 18 may drive part of the compressor section 14via a shaft (not shown) and the power turbine section 20may be arranged to drive part of the compressor section14 via a shaft (not shown) and is arranged to drive anelectrical generator 26 via a shaft 24. However, the powerturbine section 20 may be arranged to provide drive forother purposes.[0028] The combustion chamber assembly 16 isshown more clearly in figures 2, 3 and 4. The combustionchamber assembly 16 comprises a plurality of, for exam-ple eight or nine, equally circumferentially spaced tubularcombustion chambers 28. The axes of the tubular com-bustion chambers 28 are arranged to extend in generallyradial directions. The inlets of the tubular combustionchambers 28 are at their radially outermost ends andtheir outlets are at their radially innermost ends.[0029] Each of the tubular combustion chambers 28comprises an upstream wall 30 secured to the upstreamend of an annular wall 32. A first, upstream, portion 34of the annular wall 32 defines a primary combustion zone36, a second, intermediate, portion 38 of the annular wall32 defines a secondary combustion zone 40 and a third,downstream, portion 42 of the annular wall 32 defines atertiary combustion zone 44. The second portion 38 ofthe annular wall 32 has a greater diameter than the firstportion 34 of the annular wall 32 and similarly the thirdportion 42 of the annular wall 32 has a greater diameterthan the second portion 38 of the annular wall 32.[0030] A plurality of equally circumferentially spacedtransition ducts 46 are provided, and each of the transi-tion ducts 46 has a circular cross-section at its upstreamend 48. The upstream end 48 of each of the transitionducts 46 is located coaxially with the downstream end ofa corresponding one of the tubular combustion chambers28, and each of the transition ducts 46 connects and sealswith an angular section of the nozzle guide vanes.[0031] The upstream wall 30 of each of the tubularcombustion chambers 28 has an aperture 50 to allow thesupply of air and fuel into the primary combustion zone36. A radial flow swirler 52 is arranged coaxially with theaperture 50 in the upstream wall 30.[0032] A plurality of fuel injectors 56 are positioned ina primary fuel and air mixing duct 54 formed upstreamof the radial flow swirler 52. The walls 58 and 60 of theprimary fuel and air mixing duct 54 are provided with aplurality of circumferentially spaced slots 62 and 64 re-spectively which form a primary air intake to supply airinto the primary fuel and air mixing duct 54. Each circum-ferentially spaced slot 62 and 64 extends radially, longi-tudinally, in the direction of flow, of the primary fuel and

air mixing duct 54 over a distance D. The slots 62 and64 extend purely radially.[0033] A central pilot igniter 66 is positioned coaxiallywith the aperture 50. The pilot igniter 66 defines a down-stream portion of the primary fuel and air mixing duct 54for the flow of the fuel and air mixture from the radial flowswirler 52 into the primary combustion zone 36. The pilotigniter 66 turns the fuel and air mixture flowing from theradial flow swirler 52 from a radial direction to an axialdirection. The primary fuel and air is mixed together inthe primary fuel and air mixing duct 54.[0034] The primary fuel and air mixing duct 54 reducesin cross-sectional area from the intake 62, 64 at its up-stream end to the aperture 50 at its downstream end.The shape of the primary fuel and air mixing duct 54produces a constantly accelerating flow through the duct54.[0035] The fuel injectors 56 are supplied with fuel froma primary fuel manifold 68.[0036] An annular secondary fuel and air mixing duct70 is provided for each of the tubular combustion cham-bers 28. Each secondary fuel and air mixing duct 70 isarranged circumferentially around the primary combus-tion zone 36 of the corresponding tubular combustionchamber 28. Each of the secondary fuel and air mixingducts 70 is defined between a second annular wall 72and a third annular wall 74. The second annular wall 72defines the inner extremity of the secondary fuel and airmixing duct 70 and the third annular wall 74 defines theouter extremity of the secondary fuel and air mixing duct70. The second annular wall 72 of the secondary fuel andair mixing duct 70 has a plurality of circumferentiallyspaced slots 76 which form a secondary air intake to thesecondary fuel and air mixing duct 70. Each circumfer-entially spaced slot 76 extends axially, longitudinally, inthe direction of flow, of the secondary fuel and air mixingduct 70. The slots 76 extend purely axially.[0037] At the downstream end of the secondary fueland air mixing duct 70, the second and third annular walls72 and 74 respectively are secured to a frustoconical wallportion 78 interconnecting the wall portions 34 and 38.The frustoconical wall portion 78 is provided with a plu-rality of apertures 80. The apertures 80 are arranged todirect the fuel and air mixture into the secondary com-bustion zone 40 in a downstream direction towards theaxis of the tubular combustion chamber 28. The aper-tures 80 may be circular or slots and are of equal flowarea.[0038] The secondary fuel and air mixing duct 70 re-duces in cross-sectional area from the intake 76 at itsupstream end to the apertures 80 at its downstream end.The shape of the secondary fuel and air mixing duct 70produces a constantly accelerating flow through the duct70.[0039] A plurality of secondary fuel systems 82 are pro-vided, to supply fuel to the secondary fuel and air mixingducts 70 of each of the tubular combustion chambers 28.The secondary fuel system 82 for each tubular combus-

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tion chamber 28 comprises an annular secondary fuelmanifold 84 arranged coaxially with the tubular combus-tion chamber 28 at the upstream end of the secondaryfuel and air mixing duct 70 of the tubular combustionchamber 28. Each secondary fuel manifold 84 has a plu-rality, for example thirty two, of equi-circumferentially-spaced secondary fuel apertures 86. Each of the sec-ondary fuel apertures 86 directs the fuel axially of thetubular combustion chamber 28 onto an annular splashplate 88. The fuel flows from the splash plate 88 throughan annular passage 90 in a downstream direction intothe secondary fuel and air mixing duct 70 as an annularsheet of fuel.[0040] An annular tertiary fuel and air mixing duct 92is provided for each of the tubular combustion chambers28. Each tertiary fuel and air mixing duct 92 is arrangedcircumferentially around the secondary combustion zone40 of the corresponding tubular combustion chamber 28.Each of the tertiary fuel and air mixing ducts 92 is definedbetween a fourth annular wall 94 and a fifth annular wall96. The fourth annular wall 94 defines the inner extremityof the tertiary fuel and air mixing duct 92 and the fifthannular wall 96 defines the outer extremity of the tertiaryfuel and air mixing duct 92. The tertiary fuel and air mixingduct 92 has a plurality of circumferentially spaced slots98 which form a tertiary air intake to the tertiary fuel andair mixing duct 92. Each circumferentially spaced slot 98extends axially, longitudinally, in the direction of flow, ofthe tertiary fuel and air mixing duct 92. The slots 98 extendpurely axially.[0041] At the downstream end of the tertiary fuel andair mixing duct 92, the fourth and fifth annular walls 94and 96 respectively are secured to a frustoconical wallportion 100 interconnecting the wall portions 38 and 42.The frustoconical wall portion 100 is provided with a plu-rality of apertures 102. The apertures 102 are arrangedto direct the fuel and air mixture into the tertiary combus-tion zone 44 in a downstream direction towards the axisof the tubular combustion chamber 28. The apertures102 may be circular or slots and are of equal flow area.[0042] The tertiary fuel and air mixing duct 92 reducesin cross-sectional area from the intake 98 at its upstreamend to the apertures 102 at its downstream end. Theshape of the tertiary fuel and air mixing duct 92 producesa constantly accelerating flow through the duct 92.[0043] A plurality of tertiary fuel systems 104 are pro-vided, to supply fuel to the tertiary fuel and air mixingducts 92 of each of the tubular combustion chambers 28.The tertiary fuel system 104 for each tubular combustionchamber 28 comprises an annular tertiary fuel manifold106 positioned at the upstream end of the tertiary fueland air mixing duct 92. Each tertiary fuel manifold 106has a plurality, for example thirty two, of equi-circumfer-entially spaced tertiary fuel apertures 108. Each of thetertiary fuel apertures 108 directs the fuel axially of thetubular combustion chamber 28 onto an annular splashplate 110. The fuel flows from the splash plate 110through the annular passage 112 in a downstream direc-

tion into the tertiary fuel and air mixing duct 92 as anannular sheet of fuel.[0044] As discussed previously the fuel and air sup-plied to the combustion zones is premixed and each ofthe combustion zones 36, 40 and 44 is arranged to pro-vide lean combustion to minimise NOx. The products ofcombustion from the primary combustion zone 36 flowinto the secondary combustion zone 40 and the productsof combustion from the secondary combustion zone 40flow into the tertiary combustion zone 44.[0045] Some of the air, indicated by arrow A, for pri-mary combustion flows to a chamber 114 and this flowthrough the slots 62 in wall 58 into the primary fuel andair mixing duct 54. The remainder of the air, indicated byarrow B, for primary combustion flows to a chamber 116and this flow through the slots 60 in wall 56 into the pri-mary fuel and air mixing duct 54. The air, indicated byarrow C, for secondary combustion flows to the chamber116 and this flow through the slots 76 in wall 72 into thesecondary fuel and air mixing duct 70. The air, indicatedby arrow E, for tertiary combustion flows to the chamber118 and this flow through the slots 98 in wall 94 into thetertiary fuel and air mixing duct 92.[0046] The combustion process amplifies the pressurefluctuations for the reasons discussed previously andmay cause components of the gas turbine engine to be-come damaged if they have a natural frequency of a vi-bration mode coinciding with the frequency of the pres-sure fluctuations. Alternatively the amplitude of the pres-sure fluctuations may be sufficiently great to cause dam-age to the components of the gas turbine engine.[0047] The pressure fluctuations, or pressure waves,in the combustion chamber produce fluctuations in thefuel to air ratio at the exit of the fuel and air mixing ducts.The pressure fluctuations in the airflow and the constantsupply of fuel into the fuel and air mixing ducts of thetubular combustion chambers results in the fluctuatingfuel to air ratio at the exit of the fuel and air mixing ducts.[0048] Consider the equation:-

Where U is the velocity of the air, M is the mass, P is thepressure, Δu is the change in velocity, Δp is the changein pressure, FAR is the fuel to air ratio and Δ(FAR) is thechange in the fuel to air ratio.[0049] Thus in a typical fuel and air mixing duct, if Δp/Pis about 1%, then Δu/U is about 30% and hence theΔ(FAR)/FAR is about 30% into the combustion chamber.[0050] The present invention seeks to provide a fueland air mixing duct which supplies a mixture of fuel andair into the combustion chamber at a more constant fuelto air ratio. The present invention provides at least onepoint of fuel injection into the fuel and air mixing duct anda plurality of points of air injection into the fuel and air

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mixing duct. The air injection points are spaced apartlongitudinally, along the slots, in the direction of flow ofthe fuel and air mixing duct. The pressure of the air atthe longitudinally spaced air injection points at any instantin time is different. Thus as the fuel and air mixture flowsalong the fuel and air mixing duct the fuel and air mixturebecomes weaker due to the additional air. More impor-tantly the maximum difference between the actual fuelto air ratio and the average fuel to air ratio becomes rel-atively low, see line F in figure 11. However for a singlefuel injection point and a single air injection point the max-imum difference between the actual fuel to air ratio andthe average fuel to air ratio remains relatively high, seeline G in figure 11.[0051] A single point of fuel injection means that thereis one or more fuel injectors arranged at the same dis-tance from the combustion zone, or alternatively one ormore fuel injectors are arranged at a fixed time delayfrom the combustion zone. Thus the fuel injectors arearranged at a position such that the time of travel fromthe point of fuel injection to the combustion zone is thesame for all of the fuel injectors.[0052] Calculations show, see figure 12, that the vari-ation in the fuel to air ratio for a fuel and air mixing ductwith a single fuel injection point and multiple air injectionpoints are a few percent of the variation in the fuel to airratio for a fuel and air mixing duct with a single fuel in-jection point and a single air injection point if the volumeof the fuel and air mixing duct is such that the followingequation is satisfied

Where L is the length of the fuel and air mixing duct, Fis the frequency, U is the exit velocity of the fuel and airmixture and X is a number greater than 2. The greaterthe number X, the lower the variation in the fuel to airratio. For example with X = 2, the variation is about 7%,for X = 3, the variation is about 4%, for X = 4, the variationis about 3%. Preferably X is a number greater than 3,more preferably X is a number greater than 4 and morepreferably X is a number greater than 5.[0053] For a tubular combustion chamber, the frequen-cy of the lowest acoustic mode of the combustion cham-ber is

Where F is the frequency of the pressure fluctuations, cis the average speed of sound inside the combustionchamber and L is the overall length of the tubular com-bustion chamber.

[0054] For an annular combustion chamber, the fre-quency of the lowest acoustic mode of the combustionchamber is

Where F is the frequency of the pressure fluctuations, cis the average speed of sound inside the combustionchamber and D is the diameter of the annular combustionchamber.[0055] For the present invention to work effectively theair injectors, slots, need to extend over a length X suchthat

Where X is the length of the slots and U is the averagevelocity of the air inside the mixing duct. Preferably FX/U> 2.[0056] This results in the following design rules, for atubular combustion chamber X > 4LU/c or more prefer-ably X > 8LU/c and for an annular combustion chamberX > nDU/c or more preferably X > 2πDU/c.[0057] The above equations indicate that as the oper-ating temperature of the combustion chamber increases,the speed of sound increases and therefore the amountof damping by the invention increases. This is an advan-tage of the present invention.[0058] The progressive introduction of air along thelength of the fuel and air mixing duct through the slotsresults in a number of physical mechanisms which con-tribute to the reduction, preferably elimination, of thepressure fluctuations, pressure waves or instabilities, inthe combustion chamber. The physical mechanisms arethe creation of a low velocity region, integration of thefuel to air ratio fluctuations, damping of pressure wavesand destruction of phase relationships. The advantageof the slots over apertures is that there is a narrow resi-dence time distribution, hence a reduced risk of autoig-nition of the fuel, while maintaining excellent fuel to airratio characteristics.[0059] The airflow in the vicinity of the fuel injector ex-periences fluctuations in its bulk velocity due to the pres-sure fluctuations in the fuel and air mixing duct. This cre-ates a local fluctuation in fuel concentration, a local fuelto air ratio, which then flows downstream at the bulk ve-locity of the air in the fuel and air mixing duct. Due to themixing of the fuel and air in the fuel and air mixing ductthese fuel to air ratio fluctuations normally diffuse out,although the process is quite slow. However, if the localconvective velocity is low and the local turbulent intensityis high, as in the present invention, any fuel to air ratio

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fluctuations are substantially dissipated by the time thefuel to air ratio fluctuations reach the combustion cham-ber.[0060] Any fluctuation in the local fuel to air ratio in thevicinity of the fuel injector flows downstream and the pro-gressive introduction of air along the length of the fueland air mixing duct integrates out any fluctuations in thelocal fuel to air ratio due to the fuel injector. This is be-cause the pressure of the air supplied along the lengthof the slots of air injectors fluctuates with time. If the av-erage time of travel of a fluid particle from the vicinity ofthe fuel injector to the downstream end of the fuel andair mixing duct is longer than the time period of the pres-sure fluctuations, then the fluid particle originating fromthe vicinity of the fuel injector is subjected to a numberof cycles of becoming leaner and richer that average outthe initial fuel concentration fluctuation. This determinesthe spatial extent of the air injectors, i.e. the length D ofthe fuel and air mixing duct containing air injectors. Thisalso determines the width, or cross-sectional area, of thefuel and air mixing duct as this affects the total residencetime in the fuel and air mixing duct.[0061] The average air velocity through the slots is cho-sen so that the air injectors or slots are sensitive to pres-sure fluctuations originating in the combustion chamber.As a pressure wave propagates from the downstreamend of the fuel and air mixing duct towards the fuel injectorit progressively loses amplitude because energy is usedfluctuating the air pressure in the air injectors. This re-duces the possibility of the pressure fluctuations produc-ing a local fuel to air ratio fluctuation in the vicinity of thefuel injector. This also completely changes the couplingbetween the interior and exterior of the combustionchamber.[0062] A consistent relationship is required betweenthe pressure fluctuations inside the combustion chamberand the fluctuations in the chemical energy supplied tothe combustion chamber in order for the occurrence ofcombustion instability. The chemical energy input to thecombustion chamber is proportional to the strength ofthe fuel and air mixture supplied to the combustion cham-ber and the air velocity at the exit of the fuel and air mixingduct. The plurality of air injectors integrate out the pres-sure fluctuations and the fluctuations in the strength ofthe fuel and air mixture. Also any fuel to air ratio fluctu-ations present at the downstream end of the fuel and airmixing duct are uncorrelated with the pressure fluctua-tions that produced them. The possibility of positive re-inforcement of pressure fluctuations or fuel to air ratiofluctuations is reduced.[0063] Mixing of the fuel and air in the fuel and air mix-ing duct is achieved by the vortex flow set in motion bythe slots.[0064] A further advantage of the use of slots as airinjectors is that the risk of auto ignition of the fuel is re-duced because the fuel residence time in the fuel and airmixing duct is less uncertain than with a plurality ofspaced apertures. The slots eliminate the wakes and

boundary layer transverse vortices formed by the dis-crete apertures in cross flow relationship. The slots arestaggered on opposite walls to avoid a stagnation zoneon the wall opposite a slot. The slots are made as narrowas possible in order to reduce the wake at the trailingedge of the slot, typically the slots have a width of 1mm.The distance between slots is about the same as thedistance between the walls of the fuel and air mixing duct.The slots are aligned with the direction of flow of the fueland air mixture to avoid the formation of stagnant zonesin the wakes of the slots.[0065] Another advantage is that the slots create largescale vortex motion which promotes effective mixing ofthe fuel and air in the fuel and air mixing duct.[0066] Another advantage is that it is easier to make asmall number of slots than a larger number of apertures.[0067] An alternative fuel and air mixing duct 120 notforming part of the invention is shown in figures 5, 6 and7. A rectangular cross-section fuel and air mixing duct120 comprises four sidewalls 122, 124, 126 and 128. Thewalls 124 and 126 have a plurality of transversely spacedslots 130 and 132 respectively which form an air intaketo the fuel and air mixing duct 120. The slots 130 and132 extend longitudinally of the fuel and air mixing duct120. The slots 130 in the wall 124 are staggered fromthe slots 132 in the wall 128 so that each slot 130 in thewall 124 is equi-distant from two adjacent slots 132 inthe wall 128 and visa-versa. A single fuel injector 140 isprovided to supply fuel into the upstream end 134 of thefuel and air mixing duct 120. The fuel injector 140 is sup-plied with fuel from a fuel manifold 138.[0068] Another alternative fuel and air mixing duct 150not forming part of the invention is shown in figures 8, 9and 10. A circular cross-section fuel and air mixing duct150 comprises a tubular wall 152 which has a pluralityof circumferentially spaced slots 154 which form an airintake to the fuel and air mixing duct 150. The slots 154extend longitudinally, axially, of the fuel and air mixingduct 150. A single fuel injector 160 is provided to supplyfuel into the upstream end 156 of the fuel and air mixingduct 150. The fuel injector 160 is supplied with fuel froma fuel manifold.[0069] Another primary fuel and air mixing duct 170according to one embodiment of the present invention isshown in figures 13 and 14. The primary fuel and airmixing duct 170 comprises walls 174 and 176 which areprovided with a plurality of circumferentially spaced ra-dially extending slots 178 and 180 respectively whichform a primary air intake to supply air into the primaryfuel and air mixing duct 170. The slots 178 in the wall174 are staggered from the slots 180 in the wall 176 sothat each slot 178 in the wall 174 is equi-distant from twoadjacent slots 180 in the wall 176 and visa-versa. Theprimary fuel and air mixing duct 170 also has a pluralityof fuel injectors 172 positioned in the primary fuel and airmixing duct 170 upstream of the slots 178 and 180. Ad-ditionally a plurality of circumferentially spaced apertures182 are provided to form part of the primary air intake

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upstream of the fuel injectors 172. The apertures 182supply up to 40% of the primary air upstream of the fuelinjectors 172. The apertures 182 are provided to preventthe formation of a stagnant zone, a zone with no net ve-locity, at the upstream end of the primary fuel and airmixing duct 170. The stagnant zone mainly consists offuel and a small fraction of air, in operation, which resultsin long residence times for the fuel with an increased riskof auto ignition of the fuel in the primary fuel and air mixingduct 170. The apertures 182 minimise the risk of autoignition. The primary fuel and air mixing duct 170 alsoincreases in cross-sectional area, as shown, in a down-stream direction. The introduction of air upstream of thefuel injectors 172 only has a minor effect on the fuel toair ratio as shown in figure 16, where line H indicates thefluctuation in the amplitude of the fuel to air ratio in figure3 and line I indicates the fluctuation in the amplitude ofthe fuel to air ratio in figures 13 and 14.[0070] A further secondary fuel and air mixing duct 190according to another embodiment of the present inven-tion is shown in figure 15 and is similar to that shown infigure 4. The secondary fuel and air mixing duct 190 com-prises inner annular wall 194 and outer annular wall 196.The inner and outer annular walls 194 and 196 are pro-vided with a plurality of circumferentially spaced and ax-ially extending slots 198 and 200 respectively which forma secondary air intake to supply air into the secondaryfuel and air mixing duct 190. The secondary fuel and airmixing duct 190 also has an annular fuel injector slot 192positioned in the secondary fuel and air mixing duct 190upstream of the slots 198 and 200. Additionally a pluralityof circumferentially spaced apertures 202 are providedto form part of the secondary air intake upstream of thefuel injector slot 192. The apertures 202 may supply upto 20% of the secondary air, preferably up to 10% of thesecondary air. The apertures 202 also prevent the for-mation of a stagnant zone and auto ignition, at the up-stream end of the secondary fuel and air mixing duct 190.The secondary fuel and air mixing duct 190 also increas-es in cross-sectional area, as shown, in a downstreamdirection. A similar arrangement of additional aperturesmay be applied to the tertiary fuel and air mixing duct toprevent the formation of a stagnant zone and auto igni-tion.[0071] The upstream ends of the slots may be posi-tioned upstream of the fuel injectors to avoid fuel beingtrapped upstream of a vortex associated with the up-stream edge of a blunt body or air jet.[0072] The slots in the walls of the fuel and air mixingduct may be arranged perpendicularly to the walls of thefuel and air mixing duct or at any other suitable angle.[0073] The fuel supplied by the fuel injector may be aliquid fuel or a gaseous fuel.[0074] The invention is also applicable to other fuel andair mixing ducts. For example the fuel and air mixing ductsmay comprise any suitable shape, or cross-section, aslong as there are a plurality of points of injection of airarranged longitudinally in a slot, in the direction of flow

through the fuel and air mixing duct, into the fuel and airmixing duct. The slots may be provided in any one ormore of the walls defining the fuel and air mixing duct.[0075] The invention is also applicable to other air in-jectors, for example hollow slotted members may be pro-vided which extend into the fuel and air mixing duct tosupply air into the fuel and air mixing duct.[0076] The fuel and air mixing duct may have a swirler,alternatively it may not have a swirler. The fuel and airmixing duct may have two coaxial counter swirling swirl-ers. The swirler may be an axial flow swirler.[0077] Although the invention has referred to an indus-trial gas turbine engine it is equally applicable to an aerogas turbine engine or a marine gas turbine engine.

Claims

1. A tubular combustion chamber (28) comprising atleast one combustion zone (36,40,44) defined by atleast one peripheral annular wall (32), at least onefuel and air mixing duct (70,92,190) for supplying afuel and air mixture to the at least one combustionzone (36,40,44), the at least one fuel and air mixingduct (70, 92, 190) having an upstream end and adownstream end, fuel injection means (90, 112, 192)for supplying fuel into the at least one fuel and airmixing duct (70,92,190), air injection means(76,98,198,200,202) for supplying air into the at leastone fuel and air mixing duct (70,92,190), the pres-sure of the air supplied to the at least one fuel andair mixing duct (70,92,190) fluctuating, wherein theair injection means (76,98,198,200,202) comprise aplurality of air injectors (76,98,198,200) spaced aparttransversely to the direction of flow through the atleast one fuel and air mixing duct (70,92,190), eachair injector (76,98, 198, 200) comprising a slot ex-tending in the direction of flow through the at leastone fuel and air mixing duct (70,92, 190) to reducethe magnitude of the fluctuations in the fuel to airratio of the fuel and air mixture supplied into the atleast one combustion zone (36,40,44),wherein the combustion chamber (28) comprises aprimary combustion zone (36) and a secondary com-bustion zone (40) downstream of the primary com-bustion zone (36),wherein the at least one fuel and air mixing duct (70,92,190) comprises a single annular fuel and air mix-ing duct (70, 92, 190), the plurality of air injectors(76, 98, 198, 200) being circumferentially spacedapart and the plurality of air injectors (76, 98, 198,200) extending axially, in the direction of the longi-tudinal axis of the tubular combustion chamber, thesingle annular fuel and air mixing duct (70, 92, 190)comprising an inner annular wall (72, 94, 194) andan outer annular wall (74, 96, 196), the plurality ofair injectors (76, 98, 198, 200) being arranged in theinner and outer annular walls (72, 94, 74, 96, 194,

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196), characterised in that the plurality of air injec-tors (76, 98, 198)in the inner annular wall (72,94,194)are staggered circumferentially with respect to theplurality of air injectors (76,98,200)in the outer an-nular wall (74, 96, 196).

2. A tubular combustion chamber (28) comprising atleast one combustion zone (36,40,44) defined by atleast one peripheral annular wall (32), at least onefuel and air mixing duct (54,170) for supplying a fueland air mixture to the at least one combustion zone(36,40,44), the at least one fuel and air mixing duct(54,170) having an upstream end and a downstreamend, fuel injection means (56,172) for supplying fuelinto the at least one fuel and air mixing duct (54,170),air injection means (62,64,178,180,182) for supply-ing air into the at least one fuel and air mixing duct(54,170), the pressure of the air supplied to the atleast one fuel and air mixing duct (54,170) fluctuat-ing,wherein the air injection means (62,64,178,180, 182)comprise a plurality of air injectors (62,64,178,180)spaced apart transversely to the direction of flowthrough the at least one fuel and air mixing duct(54,170), each air injector (62,64,178,180) compris-ing a slot extending in the direction of flow throughthe at least one fuel and air mixing duct (54,170) toreduce the magnitude of the fluctuations in the fuelto air ratio of the fuel and air mixture supplied intothe at least one combustion zone (36,40,44),wherein the at least one fuel and air mixing duct (54,170) comprises a radial fuel and air mixing duct, theplurality of air injectors (62,64,178,180) being cir-cumferentially spaced apart and the plurality of airinjectors (62, 64, 178, 180) extending radially withrespect to the longitudinal axis of the tubular com-bustion chamber, the radial fuel and air mixing duct(54,170) comprising a first radial wall (58,174) anda second radial wall (60,176) spaced apart axially inthe direction of the longitudinal axis of the tubularcombustion chamber, the plurality of air injectors (62,64, 178, 180) being provided in the first and secondradial walls (58, 60, 174, 176),characterised in that the plurality of air injectors(62, 178) in the first radial wall (58,174) are staggeredcircumferentially with respect to the plurality of airinjectors (64, 180) in the second radial wall (60, 176).

3. A combustion chamber as claimed in claim 2 whereinthe combustion chamber comprises a primary com-bustion zone (36) and a secondary combustion zone(40) downstream of the primary combustion zone(36).

4. A combustion chamber as claimed in claim 1 or claim3 wherein the combustion chamber (28) comprisesa primary combustion zone (36), a secondary com-bustion zone (40) downstream of the primary com-

bustion zone (36) and a tertiary combustion zone(44) downstream of the secondary combustion zone(40).

5. A combustion chamber as claimed in claim 3 or claim4 as dependent on claim 3 wherein the radial fueland air mixing duct (54, 170) supplies fuel and airinto the primary combustion zone (36).

6. A combustion chamber as claimed in claim 1 or claim4 as dependent on claim 1 wherein the single annularfuel and air mixing duct (70, 190) supplies fuel andair into the secondary combustion zone (40).

7. A combustion chamber as claimed in claim 4 as de-pendent on claim 1 wherein the single annular fueland air mixing duct (92, 190) supplies fuel and airinto the tertiary combustion zone (44).

8. A combustion chamber as claimed in any of claims1 to 7 wherein the fuel injection means (172, 192) isarranged between the upstream end and the down-stream end of the or each fuel and air mixing duct(170, 190), at least a portion (182, 202) of the pluralityof air injectors (178, 180, 182, 198, 200, 202) arearranged upstream of the fuel injection means (172,192) and at least a portion (178, 180, 198, 200) ofthe plurality of air injectors (178,180,182, 198, 200,202) are arranged downstream of the fuel injectionmeans (172,192).

9. A combustion chamber as claimed in any of claims1 to 8 wherein each one of the plurality of air injectors(62,64, 76, 98, 178,180, 198, 200) at the downstreamend of the or each fuel and air mixing duct (54, 70,92, 170, 190) is arranged to supply more air into thefuel and air mixing duct than each one of the pluralityof air injectors (62, 64, 76, 98, 178, 180, 182, 198,200, 202) at the upstream end of the or each fueland air mixing duct.

10. A combustion chamber as claimed in any of claims1 to 9 wherein each one of the plurality of air injectors(62, 64, 76, 98, 178,180, 198, 200) at a first positionin the direction of flow through the or each fuel andair mixing duct (54, 70, 92, 170, 190) is arranged tosupply more air into the fuel and air mixing duct thansaid plurality of air injectors (62, 64, 76, 98, 178, 180,182, 198, 200, 202) upstream of the first position inthe fuel and air mixing duct.

11. A combustion chamber as claimed in claim 10wherein said each one of the plurality of air injectorsat the first position in the or each fuel and air mixingduct is arranged to supply less air into the fuel andair mixing duct than said plurality of air injectors(62,64, 76, 98, 178,180, 198, 200)downstream of thefirst position in the or each fuel and air mixing duct.

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12. A combustion chamber as claimed in any of claims1 to 11 wherein the volume of the or each fuel andair mixing duct (54,70,92, 170, 190) being arrangedsuch that the average travel time from the fuel injec-tion means (56,90,112, 172, 192) to the downstreamend of the fuel and air mixing duct is greater than thetime period of the fluctuation.

13. A combustion chamber as claimed in any of claims1 to 11 wherein the volume of the fuel and air mixingduct (54,70,92, 170, 190) being arranged such thatthe length of the fuel and air mixing duct multipliedby the frequency of the fluctuations divided by thevelocity of the fuel and air leaving the downstreamend of the fuel and air mixing duct is at least one.

14. A combustion chamber as claimed in claim 13wherein said volume of the or each fuel and air mixingduct being arranged such that the length of the fueland air mixing duct multiplied by the frequency of thefluctuations divided by the velocity of the fuel and airleaving the downstream end of the fuel and air mixingduct is at least two.

15. A combustion chamber as claimed in any of claims1 to 11 wherein the plurality of air injectors(62,64,76,98, 178, 180, 198, 200) extend in the di-rection of flow through each fuel and air mixing duct(54,70,92, 170, 190) over a length (D) equal to halfthe wavelength of the fluctuations of the air suppliedto the or each fuel and air mixing duct.

16. A combustion chamber as claimed in any of claims1 to 14 wherein the length (D) of an air injector(62,64,76,98, 178, 180, 198, 200) in the direction offlow through the or each fuel and air mixing duct(54,70,92, 170, 190) multiplied by the frequency ofthe fluctuations divided by the velocity of the fuel andair inside the fuel and air mixing duct is at least one.

17. A combustion chamber as claimed in claim 16wherein said length (D) of the air injector multipliedby said frequency of the fluctuations divided by saidaverage velocity of the fuel and air is at least two.

Patentansprüche

1. Eine rohrförmige Brennkammer (28), die zumindesteine Verbrennungszone (36, 40, 44), die durch zu-mindest eine ringförmige Außenwand (32) definiertwird, zumindest eine Brennstoff- und Luftmischlei-tung (70, 92, 190) zur Zufuhr eines Brennstoff- undLuftgemischs zur zumindest einen Verbrennungszo-ne (36, 40, 44), wobei die zumindest eine Brennstoff-und Luftmischleitung (70, 92, 190) ein vorgeschal-tetes Ende und ein nachgeschaltetes Ende hat, eineBrennstoffeinspritzvorrichtung (90, 112, 192) zur Zu-

fuhr von Brennstoff in die zumindest eine Brennstoff-und Luftmischleitung (70, 92, 190), eine Lufteinblas-vorrichtung (76, 98, 198, 200, 202) zur Zufuhr vonLuft in die zumindest eine Brennstoff- und Luft-mischleitung (70, 92, 190) aufweist, wobei der Druckder der zumindest einen Brennstoff- und Luft-mischleitung (70, 92, 190) zugeführten Luft fluktuiert,wobei die Lufteinblasvorrichtung (76, 98, 198, 200,202) eine Vielzahl an Luftinjektoren (76,98,198,200)umfasst, die in Abständen quer zu Richtung desStroms durch die zumindest eine Brennstoff- undLuftmischleitung (70,92,190) angeordnet sind, wo-bei jeder Luftinjektor (76, 98, 198, 200) einen Schlitzaufweist, der in der Richtung des Stroms durch diezumindest eine Brennstoff- und Luftmischleitung(70, 92, 190) verläuft, um die Zahl der Schwankun-gen im Brennstoff-Luftverhältnis des Brennstoff-Luftgemisches, das der zumindest einen Verbren-nungszone (36, 40, 44) zugeführt wird, zu reduzie-ren,wobei die Brennkammer (28) eine primäre Verbren-nungszone (36) und eine sekundäre Verbrennungs-zone (40), die der primären Verbrennungszone (36)nachgeschaltet ist, umfasst,wobei die zumindest eine Brennstoff- und Luft-mischleitung (70, 92, 190) eine einzelne ringförmigeBrennstoff- und Luftmischleitung (70, 92, 190) um-fasst, wobei die Vielzahl an Luftinjektoren (76, 98,198, 200) in Abständen rundum angeordnet ist unddie Vielzahl der Luftinjektoren (76, 98, 198, 200) axialin Richtung der Längsachse der rohrförmigen Brenn-kammer verläuft, wobei die eine ringförmige Brenn-stoff- und Luftmischleitung (70, 92, 190) eine ring-förmige Innenwand (72, 94, 194) und eine ringförmi-ge Außenwand (74, 96, 196) umfasst, wobei die Viel-zahl der Luftinjektoren (76, 98, 198, 200) in der ring-förmigen Innen- und Außenwand (72, 94, 74, 96,194, 196) angeordnet ist, dadurch gekennzeich-net, dass die Vielzahl der Luftinjektoren (76, 98,198) in der ringförmigen Innenwand (72, 94,194)rundum hinsichtlich der Vielzahl der Luftinjektoren(76, 98, 200) in der ringförmigen Außenwand (74,96, 196) versetzt ist.

2. Eine rohrförmige Brennkammer (28), die zumindesteine Verbrennungszone (36, 40, 44), die durch zu-mindest eine ringförmige Außenwand (32) definiertwird, zumindest eine Brennstoff- und Luftmischlei-tung (54, 170) zur Zufuhr eines Brennstoff- und Luft-gemischs zur zumindest einen Verbrennungszone(36, 40, 44), wobei die zumindest eine Brennstoff-und Luftmischleitung (54, 170) ein vorgeschaltetesEnde und ein nachgeschaltetes Ende hat, eineBrennstoffeinspritzvorrichtung (56, 172) zur Zufuhrvon Brennstoff in die zumindest eine Brennstoff- undLuftmischleitung (54, 170), eine Lufteinblasvorrich-tung (62, 64, 178, 180, 182) zur Zufuhr von Luft indie zumindest eine Brennstoff- und Luftmischleitung

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(54, 170) aufweist, wobei der Druck der zumindesteinen Brennstoff- und Luftmischleitung (54, 170) zu-geführten Luft fluktuiert,wobei die Lufteinblasvorrichtung (62, 64, 178, 180,182) eine Vielzahl an Luftinjektoren (62, 64, 178,180) umfasst, die in Abständen quer zu Richtungdes Stroms durch die zumindest eine Brennstoff-und Luftmischleitung (54, 170) angeordnet sind, wo-bei jeder Luftinjektor (62, 64, 178, 180) einen Schlitzaufweist, der in der Richtung des Stroms durch diezumindest eine Brennstoff- und Luftmischleitung(54, 170) verläuft, um die Zahl der Schwankungenim Brennstoff-Luftverhältnis des Brennstoff-Luftge-misches, das der zumindest einen Verbrennungszo-ne (36, 40, 44) zugeführt wird, zu reduzieren,wobei die zumindest eine Brennstoff- und Luft-mischleitung (54,170) eine radiale Brennstoff- undLuftmischleitung umfasst, wobei die Vielzahl an Luf-tinjektoren (62, 64, 178, 180) in Abständen rundumangeordnet ist und die Vielzahl der Luftinjektoren(62, 64, 178, 180) radial zur Längsachse der rohr-förmigen Brennkammer verläuft, wobei die radialeBrennstoff- und Luftmischleitung (54, 170) eine ersteradiale Wand (58, 174) und eine zweite radiale Wand(60, 176) umfasst, die axial in Richtung der Längs-achse der rohrförmigen Brennkammer angeordnetsind, wobei die Vielzahl der Luftinjektoren (62, 64,178, 180) in der ersten und zweiten radialen Wand(58, 60, 174, 176) angeordnet ist,dadurch gekennzeichnet, dass die Vielzahl derLuftinjektoren (62, 178) in der ersten radialen Wand(58, 174) rundum hinsichtlich der Vielzahl der Luf-tinjektoren (64, 180) in der zweiten radialen Wand(60, 176) versetzt ist.

3. Eine Brennkammer entsprechend Anspruch 2, wo-bei die Brennkammer eine primäre Verbrennungs-zone (36) und eine sekundäre Verbrennungszone(40), die der primären Verbrennungszone (36) nach-geschaltet ist, umfasst.

4. Eine Brennkammer entsprechend Anspruch 1 oderAnspruch 3, wobei die Brennkammer (28) eine pri-märe Verbrennungszone (36), eine sekundäre Ver-brennungszone (40), die der primären Verbren-nungszone (36) nachgeschaltet ist, und eine tertiäreVerbrennungskammer (44), die der sekundären Ver-brennungskammer (40) nachgeschaltet ist, umfasst.

5. Eine Brennkammer entsprechend Anspruch 3 oderAnspruch 4 in Abhängigkeit von Anspruch 3, wobeidie radiale Brennstoff- und Luftmischleitung (54,170) der primären Verbrennungszone (36) Brenn-stoff und Luft zuführt.

6. Eine Brennkammer entsprechend Anspruch 1 oderAnspruch 4 in Abhängigkeit von Anspruch 1, wobeidie einzelne ringförmige Brennstoff- und Luft-

mischleitung (70, 190) der sekundären Verbren-nungszone (40) Brennstoff und Luft zuführt.

7. Eine Brennkammer entsprechend Anspruch 4 in Ab-hängigkeit von Anspruch 1, wobei die einzelne ring-förmige Brennstoff- und Luftmischleitung (92, 190)der tertiären Verbrennungszone (44) Brennstoff undLuft zuführt.

8. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 7, wobei die Brennstoffeinspritzvor-richtung (172, 192) zwischen dem vorgeschaltetenEnde und dem nachgeschalteten Ende der oder je-der Brennstoff- und Luftmischleitung (170, 190) an-geordnet ist, zumindest ein Teil (182, 202) der Viel-zahl an Luftinjektoren (178, 180, 182, 198, 200, 202)der Brennstoffeinspritzvorrichtung (172, 192) vorge-schaltet ist und zumindest ein Teil (178, 180, 198,200) der Vielzahl an Luftinjektoren (178, 180, 182,198, 200, 202) der Brennstoffeinspritzvorrichtung(172, 192) nachgeschaltet ist.

9. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 8, wobei jeder der Vielzahl an Luftin-jektoren (62, 64, 76, 98, 178, 180, 198, 200) amnachgeschalteten Ende der oder jeder Brennstoff-und Luftmischleitung (54, 70, 92, 170, 190) so an-geordnet ist, dass er der Brennstoff- und Luft-mischleitung mehr Luft zuführt als jeder der Vielzahlvon Luftinjektoren (62, 64, 76, 98, 178,180, 182, 198,200, 202) am vorgeschalteten Ende der oder jederder Brennstoff- und Luftmischleitung.

10. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 9, wobei jeder der Vielzahl von Luftin-jektoren (62, 64, 76, 98, 178, 180, 198, 200) an einerersten Position in der Strömungsrichtung durch dieoder jede Brennstoff- und Luftmischleitung (54, 70,92, 170, 190) so angeordnet ist, dass sie der Brenn-stoff- und Luftmischleitung mehr Luft zuführt als diegenannte Vielzahl an Luftinjektoren (62, 64, 76, 98,178, 180, 182, 198, 200, 202), die der ersten Positionder Brennstoff- und Luftmischleitung vorgeschaltetist.

11. Eine Brennkammer entsprechend Anspruch 10, wo-bei jeder der genannten Vielzahl an Luftinjektorenan der ersten Position in der oder jeder Brennstoff-und Luftmischleitung so angeordnet ist, dass er derBrennstoff- und Luftmischleitung weniger Luft zu-führt als die genannte Vielzahl an Luftinjektoren (62,64, 76, 98, 178, 180, 198, 200) die der ersten Positionin der oder jeder Brennstoff- und Luftmischleitungnachgeschaltet ist.

12. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 11, wobei das Volumen der oder jederBrennstoff- und Luftmischleitung (54, 70, 92, 170,

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190) so angeordnet ist, dass die durchschnittlicheWegzeit von der Brennstoffeinspritzvorrichtung (56,90, 112, 172, 192) zum nachgeschalteten Ende derBrennstoff- und Luftmischleitung größer als der Zeit-raum der Schwankungen ist.

13. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 11, wobei das Volumen der Brennstoff-und Luftmischleitung (54, 70, 92, 170, 190) so an-geordnet ist, dass die Länge der Brennstoff- undLuftmischleitung multipliziert mit der Häufigkeit derSchwankungen geteilt durch die Geschwindigkeit,mit der Brennstoff und Luft aus dem nachgeschalte-ten Ende der Brennstoff- und Luftmischleitung aus-treten, mindestens eins ist.

14. Eine Brennkammer entsprechend Anspruch 13, wo-bei das genannte Volumen der oder jeder Brenn-stoff- und Luftmischleitung so angeordnet ist, dassdie Länge der Brennstoff- und Luftmischleitung mul-tipliziert mit der Häufigkeit der Schwankungen geteiltdurch die Geschwindigkeit, mit der Brennstoff undLuft aus dem nachgeschalteten Ende der Brenn-stoff- und Luftmischleitung austreten, mindestenszwei ist.

15. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 11, wobei die Vielzahl der Luftinjekto-ren (62, 64, 76, 98, 178, 180, 198, 200) in der Strö-mungsrichtung durch jede Brennstoff- und Luft-mischleitung (54, 70, 92, 170, 190) über eine Länge(D) verläuft, die der Hälfte der Wellenlänge derSchwankungen der Luft, die der oder jeder Brenn-stoff- und Luftmischleitung zugeführt wird, ent-spricht.

16. Eine Brennkammer entsprechend einem der An-sprüche 1 bis 14, wobei die Länge (D) eines Luftin-jektors (62, 64, 76, 98, 178, 180, 198, 200) in derStrömungsrichtung durch die oder jede Brennstoff-und Luftmischleitung (54, 70, 92, 170, 190) multipli-ziert mit der Häufigkeit der Schwankungen geteiltdurch die Geschwindigkeit des Brennstoffs und derLuft in der Brennstoff- und Luftmischleitung mindes-tens eins ist.

17. Eine Brennkammer entsprechend Anspruch 16, wo-bei die genannte Länge (D) des Luftinjektors multi-pliziert mit der genannten Häufigkeit der Schwan-kungen geteilt durch die genannte durchschnittlicheGeschwindigkeit von Brennstoff und Luft mindes-tens zwei ist.

Revendications

1. Une chambre de combustion tubulaire (28) compre-nant au moins une zone de combustion (36, 40, 44)

définie par au moins une paroi annulaire périphéri-que (32), au moins un conduit de mélange d’air etde combustible (70, 92, 190) destiné à fournir unmélange d’air et de combustible à la au moins unezone de combustion (36, 40, 44), le au moins unconduit de mélange d’air et de combustible (70, 92,190) possédant une extrémité amont et une extré-mité aval, un moyen d’injection de combustible (90,112, 192) destiné à fournir du combustible dans leau moins un conduit de mélange d’air et de combus-tible (70, 92, 190), un moyen d’injection d’air (76, 98,198, 200, 202) destiné à fournir de l’air dans le aumoins un conduit de mélange d’air et de combustible(70, 92, 190), la pression de l’air fournie au moinsun conduit de mélange d’air et de combustible (70,92, 190) fluctuant, où le moyen d’injection d’air (76,98, 198, 200, 202) comprend une pluralité d’injec-teurs d’air (76, 98, 198, 200) espacés transversale-ment à la direction d’écoulement au travers du aumoins un conduit de mélange d’air et de combustible(70, 92, 190), chaque injecteur d’air (76, 98, 198,200) comprenant une fente s’étendant dans la direc-tion d’écoulement au travers du au moins un conduitde mélange d’air et de combustible (70, 92, 190) defaçon à réduire la magnitude des fluctuations dansle rapport combustible sur air du mélange d’air et decombustible fourni à la au moins une zone de com-bustion (36, 40, 44),où la chambre de combustion (28) comprend unezone de combustion primaire (36) et une zone decombustion secondaire (40) en aval de la zone decombustion primaire (36),où le au moins un conduit de mélange d’air et decombustible (70, 92, 190) comprend un conduit demélange d’air et de combustible annulaire unique(70, 92, 190), la pluralité d’injecteurs d’air (76, 98,198, 200) étant espacés circonférentiellement et lapluralité d’injecteurs d’air (76, 98, 198, 200) s’éten-dant axialement dans la direction de l’axe longitudi-nal de la chambre de combustion tubulaire, le con-duit de mélange d’air et de combustible annulaireunique (70, 92, 190) comprenant une paroi annulaireinterne (72, 94, 194) et une paroi annulaire externe(74, 96, 196), la pluralité d’injecteurs d’air (76, 98,198, 200) étant agencés dans les parois annulairesinterne et externe (72, 94, 74, 96, 194, 196), carac-térisé en ce que la pluralité d’injecteurs d’air (76,98, 198) dans la paroi annulaire interne (72, 94, 194)sont circonférentiellement en quinconce par rapportà la pluralité d’injecteurs d’air (76, 98, 200) dans laparoi annulaire externe (74, 96, 196).

2. Une chambre de combustion tubulaire (28) compre-nant au moins une zone de combustion (36, 40, 44)définie par au moins une paroi annulaire périphéri-que (32), au moins un conduit de mélange d’air etde combustible (54, 170) destiné à fournir un mélan-ge d’air et de combustible à la au moins une zone

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de combustion (36, 40, 44), le au moins un conduitde mélange d’air et de combustible (54, 170) possé-dant une extrémité amont et une extrémité aval, unmoyen d’injection de combustible (56, 172) destinéà fournir du combustible dans le au moins un conduitde mélange d’air et de combustible (54, 170), unmoyen d’injection d’air (62, 64, 178, 180, 182) des-tiné à fournir de l’air dans le au moins un conduit demélange d’air et de combustible (54, 170), la pres-sion de l’air fournie au moins un conduit de mélanged’air et de combustible (54, 170) fluctuant,où le moyen d’injection d’air (62, 64, 178, 180, 182)comprend une pluralité d’injecteurs d’air (62, 64,178, 180) espacés transversalement à la directiond’écoulement au travers du au moins un conduit demélange d’air et de combustible (54, 170), chaqueinjecteur d’air (62, 64, 178, 180) comprenant unefente s’étendant dans la direction d’écoulement autravers du au moins un conduit de mélange d’air etde combustible (54, 170) de façon à réduire la ma-gnitude des fluctuations dans le rapport combustiblesur air du mélange d’air et de combustible fourni àla au moins une zone de combustion (36, 40, 44),où le au moins un conduit de mélange d’air et decombustible (54, 170) comprend un conduit de mé-lange d’air et de combustible radial, la pluralité d’in-jecteurs d’air (62, 64, 178, 180) étant espacés cir-conférentiellement et la pluralité d’injecteurs d’air(62, 64, 178, 180) s’étendant radialement par rapportà l’axe longitudinal de la chambre de combustiontubulaire, le conduit de mélange d’air et de combus-tible radial (54, 170) comprenant une première paroiradiale (58, 174) et une deuxième paroi radiale (60,176) espacées axialement dans la direction de l’axelongitudinal de la chambre de combustion tubulaire,la pluralité d’injecteurs d’air (62, 64, 178, 180) étantplacés dans les première et deuxième parois radia-les (58, 60, 174, 176),caractérisé en ce que la pluralité d’injecteurs d’air(62, 178) dans la première paroi radiale (58, 174)sont circonférentiellement en quinconce par rapportà la pluralité d’injecteurs d’air (64, 180) dans ladeuxième paroi radiale (60, 176).

3. Une chambre de combustion selon la Revendication2 où la chambre de combustion comprend une zonede combustion primaire (36) et une zone de com-bustion secondaire (4 0) en aval de la zone de com-bustion primaire (36).

4. Une chambre de combustion selon la Revendication1 ou 3, où la chambre de combustion (28) comprendune zone de combustion primaire (36), une zone decombustion secondaire (40) en aval de la zone decombustion primaire (36) et une zone de combustiontertiaire (44) en aval de la zone de combustion se-condaire (40).

5. Une chambre de combustion selon la Revendication3 ou 4 lorsqu’elle dépend de la Revendication 3, oùle conduit de mélange d’air et de combustible radial(54, 170) fournit du combustible et de l’air dans lazone de combustion primaire (36).

6. Une chambre de combustion selon la Revendication1 ou 4 lorsqu’elle dépend de la Revendication 1, oùle conduit de mélange d’air et de combustible annu-laire unique (70, 190) fournit du combustible et del’air dans la zone de combustion secondaire (40).

7. Une chambre de combustion selon la Revendication4 lorsqu’elle dépend de la Revendication 1, où leconduit de mélange d’air et de combustible annulaireunique (92, 190) fournit du combustible et de l’airdans la zone de combustion tertiaire (44).

8. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 7, où le moyen d’injectionde combustible (172, 192) est agencé entre l’extré-mité amont et l’extrémité aval du ou de chaque con-duit de mélange d’air et de combustible (170, 190),au moins une partie (182, 202) de la pluralité d’in-jecteurs d’air (178, 180, 182, 198, 200, 202) estagencée en amont du moyen d’injection de combus-tible (172, 192) et au moins une partie (178, 180,198, 200) de la pluralité d’injecteurs d’air (178, 180,182, 198, 200, 202) est agencée en aval du moyend’injection de combustible (172, 192).

9. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 8 où chaque injecteur de lapluralité d’injecteurs d’air (62, 64, 76, 98, 178, 180,198, 200) au niveau de l’extrémité aval du ou dechaque conduit de mélange d’air et de combustible(54, 70, 92, 170, 190) est agencé de façon à fournirplus l’air dans le conduit de mélange d’air et de com-bustible que chaque injecteur de la pluralité d’injec-teurs d’air (62, 64, 76, 98, 178, 180, 182, 198, 200,202) au niveau de l’extrémité amont du ou de chaqueconduit de mélange d’air et de combustible.

10. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 9 où chaque injecteur de lapluralité d’injecteurs d’air (62, 64, 76, 98, 178, 180,198, 200) au niveau d’une première position dans ladirection d’écoulement au travers du ou de chaqueconduit de mélange d’air et de combustible (54, 70,92, 170, 190) est agencé de façon à fournir plus l’airdans le conduit de mélange d’air et de combustibleque ladite pluralité d’injecteurs d’air (62, 64, 76, 98,178, 180, 182, 198, 200, 202) en amont de la pre-mière position dans le conduit de mélange d’air etde combustible.

11. Une chambre de combustion selon la Revendication10 où ledit chaque injecteur de la pluralité d’injec-

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teurs d’air au niveau de la première position dans leou dans chaque conduit de mélange d’air et de com-bustible est agencé de façon à fournir moins l’airdans le conduit de mélange d’air et de combustibleque ladite pluralité d’injecteurs d’air (62, 64, 76, 98,178, 180, 198, 200) en aval de la première positiondans le ou dans chaque conduit de mélange d’air etde combustible.

12. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 11 où le volume du ou dechaque conduit de mélange d’air et de combustible(54, 70, 92, 170, 190) est agencé de sorte que letemps de parcours moyen du moyen d’injection decombustible (56, 90, 112, 172, 192) à l’extrémité avaldu conduit de mélange d’air et de combustible estsupérieur à la période temporelle de la fluctuation.

13. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 11, où le volume du conduitde mélange d’air et de combustible (54, 70, 92, 170,190) est agencé de sorte que la longueur du conduitde mélange d’air et de combustible multipliée par lafréquence des fluctuations divisée par la vélocité ducombustible et de l’air quittant l’extrémité aval duconduit de mélange d’air et de combustible est aumoins un.

14. Une chambre de combustion selon la Revendication13 où ledit volume du ou de chaque conduit de mé-lange d’air et de combustible est agencé de sorteque la longueur du conduit de mélange d’air et decombustible multipliée par la fréquence des fluctua-tions divisée par la vélocité du combustible et de l’airquittant l’extrémité aval du conduit de mélange d’airet de combustible est au moins deux.

15. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 11, où la pluralité d’injecteursd’air (62, 64, 76, 98, 178, 180, 198, 200) s’étendentdans la direction d’écoulement au travers de chaqueconduit de mélange d’air et de combustible (54, 70,92, 170, 190) sur une longueur (D) égale à la moitiéde la longueur d’onde des fluctuations de l’air fourniau ou à chaque conduit de mélange d’air et de com-bustible.

16. Une chambre de combustion selon l’une quelconquedes Revendications 1 à 14, où la longueur (D) d’uninjecteur d’air (62, 64, 76, 98, 178, 180, 198, 200)dans la direction d’écoulement au travers du ou dechaque conduit de mélange d’air et de combustible(54, 70, 92, 170, 190) multipliée par la fréquence desfluctuations divisée par la vélocité du combustible etde l’air à l’intérieur du conduit de mélange d’air et decombustible est au moins un.

17. Une chambre de combustion selon la Revendication

16 où ladite longueur (D) de l’injecteur d’air multipliéepar ladite fréquence des fluctuations divisée par la-dite vélocité moyenne du combustible et de l’air estau moins deux.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the Europeanpatent document. Even though great care has been taken in compiling the references, errors or omissions cannot beexcluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• GB 1489339 A [0002]• WO 9207221 A [0002]• WO 920722 A [0003]

• EP 00311040 A [0006]• GB 9929601 A [0006]• US 6016658 A [0007]