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    • 专利摘要:
    ABSTRACT OF THE DISCLOSURE A flameless burner for a gas turbine engine includes a burner body having a longitudinalaxis, an upstream section and a doWnstream section. The upstream section of the burner bodydef1nes a primary sWirl generating chamber having air sWirlers associated thereWith. Theprimary swirl generating chamber is adapted and configured to receive compressor discharge airthrough the air sWirlers. The strong sWirl of the compressor discharge air forrns a recirculationzone that entrains combustion product gases toward the burner body. Fuel injectors areoperatively connected to the doWnstream section of the burner body for issuing fuel into the recirculated combustion product gases.
    公开号:SE535112C2
    申请号:SE1050460
    申请日:2010-05-10
    公开日:2012-04-17
    发明作者:Michael D Cornwell；Nicholas R Overman；Ephraim Gutmark
    申请人:Delavan Inc；
    IPC主号:
    专利说明:

    1. Field of the InventionThe present invention relates to gas turbine engines, and more particularly, to bumers for combustors in gas turbine engines. 2. Description of Related ArtA variety of devices and methods are known in the art for injecting fuel into gas turbine engines. Of such devices, many are directed to injecting fuel into combustors of gas turbineengines to sustain combustion under lean conditions. Lean combustion is desirable for lowpower settings in gas turbine engines because it is fuel efficient and can produce relatively lowlevels of undesirable emissions. Aero gas turbine engines have progressively been designed tooperate leaner and leaner in order to reduce NOX emissions. Industrial gas turbine engines havebeen switching to lean partially premixed combustion to operate lean, primarily to lower NOXproduction rates. However, the trend toward lean combustion has been impeded by operabilityconcerns. Very lean combustion has proven to be very unstable. Flames produced in leanconditions tend to be unstable and if left unchecked the instability can result in lean flame blowout. Moreover, even if lean blow out does not occur, instabilities in lean combustion can resultin strong acoustic waves that can cause undesirable noise and stress within the structures of a gasturbine engine. Measures can be taken to mitigate instabilities and control the combustion process to improve flame stability. However, at very lean conditions, e.g., below around 0.60 equivalence ratio for a gas turbine using liquid fiJel, conventional methods may not be enough toprovide the desired stability.
    One way of providing stable combustion at very lean conditions is to use a flamelesscombustion process. Most combustion instabilities involve a three part cyclic process, wherefluid mechanical phenomena result in a fluctuation in heat release rate that couples andreinforces an acoustic mode, which in turn trips an unstable fluid dynamic structure, which leadsto fluctuations in heat release rate, and so on. In flameless combustion, such a coupling does notoccur. The inability of coupling of this kind to occur in flameless combustion inhibits strongacoustic waves that could otherwise damage the combustor or turbine blades.
    Flameless combustion has been successfially demonstrated in industrial fiJmaces. Thetechnique involves using a very lean mixture wherein high temperature oxidizer reacts with fuelat very high levels of turbulence in a distributed reaction zone. Flameless combustion has beenshown to produce very stable combustion having low NOX levels in industrial fiJmaces. Thiscombustion method is called “flameless combustion” because of the lack of a discrete visibleflame resulting from the distributed nature of the reaction. In industrial furnace applications offlameless combustion, the high oxidizer temperatures required are obtained by either preheatingthe air with furnace exhaust gases through a heat exchanger or by direct mixing of the air withhot recirculated exhaust gas. These fumaces typically recycle combustion gases via a ductextemal to the combustion region. These ducts and/or heat exchangers in conventional burnershave limited the application of flameless combustion to ground based operations.
    Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, there is still a need for improved devices and methods for producing flameless combustion Without recirculation ducts or heat exchangers. The present invention provides a solution for these problems.
    SUMMARY OF THE INVENTION The subject invention is directed to a new and useful flameless bumer for a gas turbineengine. The flameless bumer includes a bumer body having a longitudinal axis, an upstreamsection and a downstream section. The upstream section of the bumer body defines a primaryswirl generating chamber having an air swirler associated therewith. The primary swirlgenerating chamber is adapted and configured to receive compressor discharge air through theair swirler thereby forrning a recirculation zone that entrains downstream combustion productgases toward the bumer body. The burner also includes fiiel injection means operativelyconnected to the downstream section of the bumer body for issuing fiiel into the recirculatedcombustion product gases.
    The air swirler of the upstream section of the bumer body can be a radial air swirler. Asecond radial air swirler can be defined between the primary swirl generating chamber and thedownstream section of the burner body. A conical air swirler can be defined in the downstreamsection of the bumer body proximate the primary swirl generating chamber. The flamelessbumer can include a diverging diffuser section defined in the downstream section of the bumerbody. A second air swirler can be defined in the diffuser section for injecting a swirling flow ofcompressor discharge air into the diffuser section. The first air swirler can be a radial swirler,and the second air swirler can be a conical swirler. It is also contemplated that the first andsecond air swirlers can both be radial swirlers.
    The fiael injection means can include a plurality of fiiel injector extension tubes extendingdownstream from the downstream section of the bumer body with the injector extension tubesangled obliquely inward to inject fuel into recirculated combustion product gases. The fuel injection means can include at least one fuel injector having an exit orifice defined in a doWnstream facing surface proximate a throat portion of the bumer body defined between theprimary sWirl generating chamber and the doWnstream section of the bumer body. In anotheraspect, the fuel injection means can include a plurality of fuel injectors, each having an eXitorif1ce defined in an inWard facing surface of a diffuser in the doWnstream section of the bumerbody. The primary sWirl generating chamber and air sWirler can be configured to introduce asWirling floW of compressor discharge air into the primary sWirl generating chamber in asubstantially purely tangential direction. An upstream fuel injector can be defined in anupstream portion of the primary sWirl generating chamber.
    The upstream, doWnstream, and throat portions of the bumer body can form aconVerging, diVerging interior profile that conVerges proximate the throat portion. The throatportion of the bumer body can include a plurality of secondary fuel injectors. Each of the fuelinjectors can include an atomizing fuel nozzle configured to issue a et of fuel that is co-injectedWith compressor discharge air to promote thorough fiJel and air mixing prior to auto-ignition.
    The primary sWirl generating chamber, air sWirler, and fuel inj ector can be configuredand adapted to sustain a flameless combustion reaction Wherein the fuel to air ratio is beloWabout 0.4. The primary sWirl generating chamber, air sWirler, and fuel injector can be configuredand adapted to sustain a flameless combustion reaction Wherein CO emissions are beloW about10 ppm, and/or NOX emissions are below about 10 ppm. The primary sWirl generating chamberand air sWirler can be configured to deVelop a sWirling floW Within the primary sWirl generatingchamber to establish a mixture of combustion product gases and compressor discharge air Withina recirculation zone Wherein the ratio of combustion product to compressor discharge air is at least about 2.5 to about 1.0.
    These and other features of the devices and methods of the subject invention Will becomemore readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction With the draWings.
    BRIEF DESCRIPTION OF THE DRAWINGS The patent or application file contains at least one drawing executed in color. Copies ofthis patent or patent application publication with color drawing(s) will be provided by the Officeupon request and payment of the necessary fee.
    So that those skilled in the art to which the subject invention appertains will readilyunderstand how to make and use the methods and devices of the subject invention without undueexperimentation, preferred embodiments thereof will be described in detail herein below withreference to certain figures, wherein: Fig. l is a perspective view of a portion of a combustor of a gas turbine engine includinga representative embodiment of three flameless burners constructed in accordance with thepresent invention, showing the arrangement of bumers within the combustor; Fig. 2 is a perspective view of a portion of the combustor of Fig. l, showing one of theflameless bumers separated from the combustor; Fig. 3 is a partially exploded perspective view of the flameless burner of Fig. 2, showinghow the fuel lines connect to the bumer; Fig. 4 is a cross-sectional side elevation view of the flameless bumer of Fig. 3, showingthe internal fuel and air passages of the bumer; Fig. 5 is a cross-sectional side elevation view of a portion of the burner of Fig. 4, showingfuel issuing through one of the fuel nozzles; Fig. 6 is a cross-sectional side elevation view of a portion of the combustor of Fig. l, showing a schematic representation of flow in the bumer and combustor; Fig. 7 is a perspective View of a portion of a combustor of a gas turbine engine includinganother representative embodiment of three flame1ess bumers constructed in accordance with thepresent inVention, showing the arrangement of bumers within the combustor; Fig. 8 is a partia11y exp1oded perspective View of the combustor and one of the flame1essbumers of Fig. 7, showing how the burner connects to the combustor; Fig. 9 is an exp1oded cross-sectiona1 side e1eVation View of the flame1ess bumer of Fig. 8,showing the primary swir1 generating chamber, air swir1ers, and fi1e1 injectors; Fig. 10 is a cross-sectiona1 side e1eVation View of the flame1ess bumer of Fig. 9, showingthe air and fue1 flow passages through the bumer; Fig. 11 is a cross-sectiona1 side e1eVation View of a portion of the flame1ess bumer of Fig.10, showing fi1e1 issuing through a secondary fi1e1 nozzle; Fig. 12 is a cross-sectiona1 side e1eVation View of a portion of the flame1ess bumer of Fig.10, showing fue1 issuing through a primary fi1e1nozz1e; Fig. 13 is a cross-sectiona1 side e1eVation View of a portion of the combustor of Fig. 7,showing a schematic representation of air flow in the bumer and combustor; Fig. 14 is a p1ot of CO emissions oVer a range of combustion temperatures for seVendifferent fue1 types in an exemp1ary flame1ess bumer constructed in accordance with the presentinVention; Fig. 15 is a p1ot of NOX emissions oVer a range of air/fue1 equiVa1ence ratios, whichcorresponds to the range of combustion temperatures in Fig. 14, for nine different fue1 types inthe flame1ess bumer ofFig. 14; Fig. 16 is a series of photographs of conditions within the test apparatus of the flame1ess bumer of Fig. 14, showing combustion characteristics across a range of air/fue1 ratios; Fig. 17 is a series of310 nm waVe1ength images of combustion in the flame1ess bumer ofFig. 14, showing conditions for Jet-A fi1e1, 12% AP for six different air/ fi1e1 ratios; Fig. 18 is a p1ot of temperature oVer a range of radia1 positions for the f1ame1ess bumer ofFig. 14 at an equiVa1ence ratio of 0.55, showing the temperature profi1e at fiVe different aXia11ocations; Fig. 19 is a p1ot of temperature oVer a range of radia1 positions for the f1ame1ess bumer ofFig. 14 at an equiVa1ence ratio of 0.35, showing the temperature profi1e at fiVe different aXia11ocations; and Fig. 20 is a group of p1ots showing temperature oVer a range of axia1 and radia1 1ocationsin the f1ame1ess burner of Fig. 14 for fiVe different flow rates, as we11 as a p1ot of temperature over a range of equivalence ratios for four 1ocations and two different fi1e1 types.
    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made to the drawings wherein like reference nurnerals identifysimilar structural features or aspects of the subject invention. For purpose of explanation andillustration, and not limitation, a partial view of an exernplary ernbodirnent of a flarneless burnerin accordance with the invention is shown in Fig. 1 and is designated generally by referencecharacter 100. Other ernbodirnents of flarneless burners in accordance with the invention, oraspects thereof, are provided in Figs. 2-13, as will be described. The systern of the invention canbe used in gas turbine engines, or in any other suitable application, for sustaining stableflarneless cornbustion.
    As shown in Fig. 1, flarneless burners 100 are adapted for use in gas turbine engines, andcan be arranged around a typical cornbustor 10. It is conternplated that flarneless burners 100can be used as the exclusive rneans of injecting fuel into cornbustor 10. It is also conternplatedthat flarneless burners 100 can be interspersed with traditional fuel injectors within cornbustor10. As indicated in Fig. 2, burner 100 is configured to be attached to cornbustor 10 by attachinga collar ring 30 to the cornbustor aperture 20. Any suitable attachrnent rnethod can be used,including welding, brazing, or use of fasteners, such as are typically used to attach traditionalfuel injectors to cornbustors. As shown in Fig. 3, fuel lines 40 are attached to burner 100 fordelivering fuel frorn a source external to cornbustor 10 through burner 100 into the interior ofcornbustor 10.
    Fig. 4 shows a cross-section of flarneless burner 100. Burner 100 includes a burner body102 having a longitudinal axis 104, an upstream section 106 and a downstrearn section 108. Theupstrearn section 106 of burner body 102 defines a prirnary swirl generating charnber 110 having an air swirler 112 associated therewith. Prirnary swirl generating charnber 110 is adapted and configured to receive compressor discharge air through air swirler 112 so that the high swirlinduced by the flow of compressor discharge air results in Vortex breakdown and recirculates(entrains) the combustion products from downstream into primary swirl generating chamber 110.
    Air swirler 1 12 of upstream section 106 of bumer body 102 is a radial air swirler. Asecond radial air swirler 118 is defined between primary swirl generating chamber 110 anddownstream section 108 of bumer body 102. Flameless bumer 100 has a diVerging diffusersection 120 defined in downstream section 108 of burner body 102. Air swirler 118 is defined indiffuser section 120 for injecting a swirling flow of compressor discharge air into diffuser section120. Primary swirl generating chamber 110 and air swirler 112 are configured to introduce aswirling flow of compressor discharge air into primary swirl generating chamber 110 in asubstantially purely tangential direction. HoweVer, those skilled in the art will readily appreciatethat any suitable swirler configuration can be used without departing from the spirit and scope ofthe invention, provided the swirl strength is sufficient to entrain combustion product gases tosustain flameless combustion.
    Bumer 100 also includes fuel injector tips 123 and injector extension tubes 122operatiVe1y connected to downstream section 108 of bumer body 102 for issuing fuel intoupstream flowing recirculation zone 116, which includes entrained combustion product gases(not shown in Fig. 4, but see Fig. 6). Injector extension tubes 122 inject both fuel andcompressor discharge air. Fuel is partially or fully Vaporized within injector extension tubes 122.Fuel injector tips 123 perform the fuel injection or atomization of fuel routed through injectorextension tubes 122. As indicated in Figs. 4 and 5, injector extension tubes 122 extenddownstream from downstream section 108 and are angled obliquely inward to inject fuel into the entrained combustion product gases included in recirculation zone 116. 11 A throat portion 124 is defined at a narroW region of the interior of nozzle body 102between primary sWirl generating chamber 110 and diffuser section 120. Upstream,doWnstream, and throat portions 106/ 108/ 124 of bumer body 102 forrn a conVerging, diVerginginterior profile that conVerges proximate throat portion 124. The conVergent-diVergent sectionstabilizes the stagnation point of the Vortex producing a more stable recirculation zone as Well asstabilizing the sWirl Within the recirculation chamber. This conVerging diVerging structurepreVents recirculating combustion products from entering primary sWirl generating chamber 110upstream of throat portion 124.
    Fig. 6 shoWs a schematic representation of the floW pattem of air and combustionproducts developed Within bumer 100 and combustor 10 during operation. Compressordischarge air 130 is passed into the interior of bumer 100 through sWirlers 112 and 118 in apurely or nearly purely tangential direction With respect to central axis 104 of bumer body 102.This creates a Vortex 132 extending into the interior of combustor 10. Air also enters throughinjector extension tubes 122. The interior portion of Vortex 132 has a loWer pressure than itssurroundings, and since Vortex 132 extends Well Within combustor 10, combustion dischargegases of recirculation zone 116 are entrained Within Vortex 132 and are conVeyed back as farupstream as a stagnation point just doWnstream of throat 124. ector extension tubes 122 haVeoutlets Within or in close proximity to the recirculated combustion discharge gases inrecirculation zone 116 so as to be able to inject fuel into the recirculated or entrained combustiondischarge gases of recirculation zone 116. Since combustion discharge gases typically haVe atemperature in a range, for example from around 900° C to about 1800° C, depending onequiValence ratio, or below about 1200° C for Very lean combustion, there is sufficient heat to sustain combustion of fuel injected from injector extension tubes 122. 12 With continued reference to Fig. 6, the combustion air flow exiting bumer 100 has astrong swirl that is induced by swirlers 112 and 118 and induces the strong swirl of Vortex 132 ofthe combustion products in chamber 10 causing Vortex breakdown that generates a recirculationzone 116 in the center of chamber 10. This recirculation zone 116 carries hot and oxygendepleted combustion products upstream up to the upstream stagnation point (located at throat124 as shown in Fig. 4) and then down stream as indicated by arrows 134. During this upstreamand downstream motion, the flows mix with the fuel jets that are injected through injectorextension tubes 122 and ignite them. Some of the combustion also occurs in the extemalrecirculation zones 136.
    Downstream flowing mixed flow 134 can include incoming air or previouslyrecirculating gases, due to the strong mixing taking place in chamber 10 between freshcombustion air, hot combustion products, and fuel, which strong mixing is a characteristic offlameless combustion. A shear zone exists between upstream flowing recirculating compressordischarge gases in recirculation zone 116 and downstream flowing mixed flow 134 flowingfrom the bumer through combustor 10 to a downstream turbine (not shown). Vortex 132 resideswithin this shear zone. Additionally, outer recirculation zones 136 develop in the comers ofcombustor 10 adjacent the outlet of bumer 100. Another shear zone exists between downstreamflowing mixed flow 134 and the recirculating gases 136. Arrows 138 schematically indicate atangential flow component that is present through the entire chamber, including upstream anddownstream flowing gases. The circumferential flow 138 is larger near the walls of chamber 10.Flow 138 is not required for flameless combustion, but is a product of the strong swirl induced by bumer 100. 13 The combination of the various flow components results in an overall flow pattern thatpromotes mixing of fuel, compressor discharge air, and combustion product gases. The result isa substantially uniforrn combustion reaction in which there is no distinct flame front. The fuel issupplied from injector extension tubes 122, the oxygen is supplied from the compressordischarge air 130 as well as unused oxygen from the combustion products, and the heat forsustained combustion comes from recirculated combustion product gases. Sustained combustiondoes not need to come from a distinct flame front, coupled with flow instabilities and acoustics,as in traditional combustors. Instead, the combustion reaction is distributed in a generallyuniform manner that closely approximates the well-mixed ideal. The resulting combustionreaction has excellent flame stability even at very lean mixtures as is typical of known flamelesscombustion systems. However, since the swirl induced by the compressor discharge air is usedto entrain the combustion product gases for sustaining the combustion reaction, none of theheavy recirculation ducts or heat exchangers typical of known flameless combustors are requiredto achieve flameless combustion. The conditions required to obtain the flameless mode ofoperation are: high turbulence for strong mixing, high temperature and low oxygen concentrationin the mixed combustion air and combustion products where they mix with the fuel. Bumer 100enables these conditions to be achieved while also having an acceptable pressure drop ofapproximately 4%, which is important for high efficiency in gas turbine engines.
    Primary swirl generating chamber 110, air swirlers 112/118, and injector extension tubes122 are configured and adapted to sustain a flameless combustion reaction wherein the fuel to airratio is below about 0.4. The transition from non-flameless mode to a flameless mode is gradual.As the air/fuel ratio is reduced below around 0.6, it gradually transitions to a flameless mode.
    Low emissions characteristics can also be sustained at a higher filel to air ratio than 0.4, but at 14 signif1cant1y higher Va1ues, e.g., greater than about 0.6, the combustion is not distributed andcannot be described as flame1ess. HoWeVer, eVen at these higher fue1/air ratios, bumer 100provides combustion that is sti11 stab1e and has 1oW emissions. Those ski11ed in the art Wi11therefore appreciate that the transition equiVa1ence ratios proVided herein are exemplary and thatbumers haVing any suitable transition equiVa1ence ratio can be uti1ized Without departing fromthe spirit and scope of the inVention.
    Primary sWir1 generating chamber 110, air sWir1ers 112/1 18, and injector extension tubes122 can sustain a flame1ess combustion reaction Wherein NOX emissions are be1oW about 10ppm and CO emissions be1oW about 10 ppm. Previous gas turbine techno1ogies can eitherproVide such 1oW NOX emissions, at 1ean equiVa1ence ratios, or such 1oW CO emissions, but notboth at the same equiVa1ence ratio. In preVious gas turbine techno1ogies, NOX emissions tend tobe reduced as the equiVa1ence ratio approaches 1ean b1oW out, but CO emissions tend to increaseas the equiVa1ence ratio approaches 1ean b1oW out. Primary sWir1 generating chamber 110 and airsWir1er 112 deVe1op a sWir1ing floW Within primary sWir1 generating chamber 110 to estab1ish amixture of combustion product gases and compressor discharge air Within a recircu1ation zoneWherein the ratio of combustion product to compressor discharge air is at 1east about 2.5 to about1.0.
    Fig. 7 shows a portion of combustor 10 haVing three bumers in accordance With anotherexemp1ary embodiment of a flame1ess bumer 200. Bumer 200 is staged to supp1y fue1 tocombustor 10 in a primary stage and a secondary stage, as indicated by fue1 floW arroWs in Fig.7. As indicated in Fig. 8, Bumer 200 attaches to combustor 10 by Way of co11ar 45 and fasteners 47, hoWeVer, any other suitab1e method of j oining can be used.
    As shown in Figs. 9 and 10, burner 200 includes an upstream portion 206 def1ning aprimary swirl generating Chamber 210, air swirler 212, and a downstream portion 208 much asdescribed above with respect to bumer 100. Throat 224, conical swirler 218, and diffuser section220 are separate components assembled into bumer 200, as indicated in Fig. 9. Fig. 10 showssecondary fuel injectors 223, each having an exit orifice defined in a downstream facing surfaceof throat portion 224. Fuel circuitry is shown in Fig. 10 for conducting secondary fuel throughcentral conduit 225 to secondary fuel injectors 223. Fig. 11 shows an enlarged View of fuelissuing through the fuel circuitry and out through injector 223. Downstream portion 208includes a plurality of primary fuel injectors 222, each haVing an exit orif1ce defined in aninward facing surface of diffuser 220. Fig. 12 shows an enlarged View of fuel issuing throughthe fuel circuitry and out through injector 222, which fuel enters burner 200 through inlet 227(see Fig. 8). Each of the fuel injectors 222/223 can include an atomizing fuel nozzle conf1guredto issue a j et of fuel that is co-injected with compressor discharge air to promote thorough fueland air mixing prior to auto-ignition. Optionally, one or more additional fuel injectors could belocated in the upstream-most surface of primary swirl generating chamber 210. Those skilled inthe art will readily appreciate that any suitable type of nozzles can be used in conjunction withinjectors as described herein, that the designations “primary” and “secondary” herein are used forclarity only, and that traditional roles of primary and secondary fuel injectors can be altered orreversed as needed without departing from the spirit and scope of the inVention.
    Fig. 13 shows a schematic representation of the flow pattem created by bumer 200 incombustor 10. Compressor discharge air 230 is passed into the interior of bumer 200 throughswirlers 212 and 218 in a purely or nearly purely tangential direction. Air also enters around injectors 222 (as shown in Figs. 10 and 12), but not through upstream injectors 223. Those 16 skilled in the art Will appreciate that injectors 223 could be modified to include an air flow as ininjectors 222. When injectors 222 and/or 223 are conf1gured to inject air and fuel, they can beused as an air assist circuit. This creates a vortex 232, entrains combustion discharge gases in arecirculation zone 216, provides downstream flowing mixed flow 234, outer recirculation zones236, and a tangential flow component 238, much as those described above with reference to Fig.6. Fuel injectors 222/223 have outlets in close proximity to the recirculated combustiondischarge gases in recirculation zone 216 so as to be able to inject fuel into the combustiondischarge gases 216. lnjectors 222/223 take a greater pressure drop compared with injectors 123with injector extension tubes 122 described above. Injectors 222/223 provide sufficient fuelmomentum to allow penetration of the fiJel into the flow field such that fiJel penetrates the vortexand is entrained into recirculation zone 216. Thus, extension tubes are not needed to pierce thevortex and directly deposit fuel into recirculation zone 216. lnjectors 222/223 can be atomizertips, discrete jet injectors, or any other suitable injection means that can provide sufficient fiJelmomentum.
    A bumer was constructed substantially as described above with respect to bumer 100,shown in Figs. 3-5. The bumer was tested in a test chamber. The plots in Figs. 14 and 15 showboth CO & NOX concentrations over a range of equivalence ratios, with flame temperaturedirectly related to equivalence ratio on the horizontal axes of the plots. A variety of fuels wastested, with the most important for gas turbine engines being J et-A. Results for J et-Ademonstrated emissions of CO below 10ppm for an equivalence ratio above approximately 0.36,and NOX below 10ppm for an equivalence ratio below about 0.43. Thus there is a range betweenabout 0.36 - 0.43 in which both CO & NOX emissions are simultaneously below 10ppm. The tested design incorporated fuel staging to increase the range of ultra-low emissions. However, 17 the transition into flameless regime and ultra-low emissions is only gradual and emissionconcentrations increase slowly until near lean-blow-out.
    The flame structure generated through flameless combustion parallels that of a wellstirred reactor. For an equiValence ratio aboVe approximately 0.40 for J et-A, the flame structureproduced by the bumer resembles that of traditional gas turbine injectors in which a distinctflame shape can be deterrnined from the concentration of OH & CH radicals. HoweVer, at lowerequiValence ratios, the flame shape is no longer discemable as depicted by the wide and eVenlyspread OH and CH radicals. When the radicals of combustion encompass the majority of thecombustion chamber and a flame shape can no longer be discerned it can be said that thecombustion process is in the flameless regime.
    As shown in the images of Fig. 16 and 17, at equiValence ratios aboVe approximately .40the flame is anchored by the recirculation zone: those skilled in the art will recognize this as aswirl stabilized flame classically used in gas turbine engines. This type of flame is prone toinstabilities as perturbations in the forward stagnation point of the Vortex can couple with theflame. When combustion is in the flameless regime the flame is no longer anchored or stabilizedat a single point or by the central Vortex, therefore, perturbations in fluid structure haVe littleeffect on the combustion process. In Fig. 16, the lean blow out indicated refers to lean blow outon the test apparatus.
    The test design successfully performed combustion in the flameless regime, but hadasymmetries of fuel distribution that limited performance. This can be corrected by using animproVed intemal fuel manifold and eliminating large Variations in the length and position of the fuel extension tubes. 18 Due to the distributed nature of flameless combustion, the temperature distribution is alsoimproved above that of classic gas turbine injectors. Again, Viewing the burner at a highequiValence ratio, the temperature distribution is similar to classic injectors With highertemperatures near the center of the combustor and cooler temperatures near the Wall, as shown inFig. 18, Where r/DC = 0.0 corresponds to the center of the combustor and r/DC = 0.5 correspondsto the Wall. This behaVior is exhibited only for the curVes taken 6” ”, 8”, and 10” doWnstream ofthe bumer because the curVes taken at 2” and 4” distances are so close to the bumer that theflow Was not as deVeloped. The higher central temperatures are a strong producer of therrnalNOX as Well placing larger therrnal stresses on the turbine section doWnstream. The flamelessregime results in the same bulk or aVerage temperature across the combustor but at any diametricposition the temperature is much closer to the aVerage, as indicated in Fig. 19. In Figs. 18 and19, the Various curVes are plotted at different locations along the length of the combustor, asindicated by the key in Fig. 19. In the cases shoWn in Fig. 19, the temperature is relatiVelyuniform at a length-to-diameter ratio of 0.75. Beyond that the temperature remains uniform butdecreases indicating complete combustion by the axial position of 0.75 L/D, or only 6 inches.Beyond the 0.75 L/D ratio heat is lost through the combustor Walls, Which are exposed to nearSTD conditions.
    Fig. 20 shoWs f1Ve plots of temperature data taken from the test apparatus. An array oftherrnocouples Was transVerse across the floW in the test apparatus to obtain temperature data atVarious axial and radial locations, as indicated in the f1Ve area plots. Each plot corresponds to adifferent floW rate in the bumer, as indicated. Fig. 20 also shoWs a plot of temperature as afunction of equiValence ratio for three therrnocouples in the exhaust and a therrnocouple placed in the throat of the recirculation chamber upstream of fuel injection, labeled “Recirculation TC” 19 in Fig. 20. The recirculation therrnocouple demonstrated temperatures in the recirculation zoneapproximate those of combustion, indicating that recirculation of the hot combustion gases intothe throat area of the bumer does occur.
    The methods and systems of the present invention, as described above and shown in thedrawings, provide for flameless combustion with superior properties including no need for heavyrecirculation ducts or heat eXchangers as in previously known flameless bumers. Thisimprovement allows for the benefits of flameless combustion for gas turbine engines in anaircraft setting, as well as in ground-based gas turbine engines, or any other gas turbine enginesetting. While the apparatus and methods of subject invention have been shown and describedwith reference to preferred embodiments, those skilled in the art will readily appreciate thatchanges and/or modifications may be made thereto without departing from the spirit and scope of the subject invention.
    权利要求:
    Claims (13)
    [1] 1. What is claimed is: A flarneless burner for a gas turbine engine cornprising: a) a burner body having a 1ongitudina1 axis, an upstrearn section and a downstrearnsection, the upstrearn section of the burner body defining a primary swirl generatingcharnber having an air swirler associated therewith, Wherein the prirnary swirlgenerating charnber is adapted and configured to receive cornpressor discharge airthrough the air swirler and thereby forrn a recirculation zone that entrains downstrearncornbustion product gases toward the burner body; and b) a p1ura1ity of fi1e1 injectors, each having an exit orifice defined in an inWard facingsurface of a diffilser in the downstrearn section of the burner body for issuing fi1e1 into recircu1ated cornbustion product gases. A flarneless burner as recited in clairn 1, Wherein the air swirler of the upstrearn section of the burner body is a radia1 air swirler. A flarneless burner as recited in clairn 2, fiJrther cornprising a second radia1 air swirler defined between the prirnary swirl generating charnber and the downstrearn section of the bumer body. A flarneless burner as recited in clairn 2, fiJrther cornprising a conica1 air swirler defined in the downstrearn section of the burner body proxirnate the prirnary swirl 21 generating chamber. A flame1ess burner as recited in c1aim 1, fiJrther comprising at 1east one fi1e1 injectorhaving an exit orifice defined in a downstream facing surface proximate a throatportion of the bumer body defined between the primary swir1 generating chamber and the downstream section of the bumer body. A flame1ess bumer for a gas turbine engine comprising: a) a bumer body haVing an upstream section, a downstream section, and a throatportion defined between the upstream and downstream sections, the upstream sectiondefining a primary swir1 generating chamber haVing a first air swir1er associatedtherewith, wherein the primary swir1 generating chamber is configured to receiVecompressor discharge air through the first air swir1er and thereby form a recircu1ationzone that entrains downstream combustion product gases toward the bumer body; b) a diVerging diffiJser section defined in the downstream section of the bumer bodywith a second air swir1er defined in the diffiJser section for injecting a swir1ing flowof compressor discharge air into the diffiJser section; and c) a p1ura1ity of primary fuel injectors operatiVe1y connected to the bumer bodyconfigured to inject fi1e1 into recircu1ated combustion product gases and compressordischarge air, each primary fi1e1 injector haVing an exit orifice defined in an inward facing surface of a diffiJser in the downstream section of the bumer body. 22 10. 11. 12. 13. A flame1ess bumer as recited in c1aim 6, fiJrther comprising an upstream fi1e1 injector defined in an upstream portion of the primary sWir1 generating Chamber. A flame1ess bumer as recited in c1aim 6, Wherein the first air sWir1er is a radia1 sWir1er, and Wherein the second air sWir1er is a conica1 sWir1er. A flame1ess bumer as recited in c1aim 6, Wherein the upstream, doWnstream, andthroat portions of the bumer body form a conVerging, diverging interior profi1e that conVerges proximate the throat portion. A flame1ess bumer as recited in c1aim 6, Wherein the throat portion of the bumer body includes a p1ura1ity of secondary fi1e1 injectors. A flame1ess bumer as recited in c1aim 6, Wherein the first and second air sWir1ers are both radia1 sWir1ers. A flame1ess bumer as recited in c1aim 6, Wherein each of the primary fi1e1 injectorsincludes an atomizing fi1e1nozz1e configured to issue a jet of fi1e1 that is co-injectedWith compressor discharge air to promote thorough fi1e1 and air mixing prior to auto- ignition. A flame1ess bumer for a gas turbine engine comprising: a) a bumer body haVing a 1ongitudina1 axis, an upstream section and a doWnstream 23 section, the upstream section of the bumer body defining a primary sWir1 generatingChamber having an air sWir1er associated thereWith, Wherein the primary sWir1generating chamber is adapted and configured to receive compressor discharge airthrough the air sWir1er and thereby form a recirculation zone that entrains doWnstreamcombustion product gases toward the bumer body; and b) at least one fiJeI injector having an exit orifice defined in a doWnstream facingsurface proximate a throat portion of the bumer body defined between the primarysWir1 generating chamber and the doWnstream section of the bumer body for issuing fiael into recirculated combustion product gases. 24
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    US12/454,137|US8667800B2|2009-05-13|2009-05-13|Flameless combustion systems for gas turbine engines|
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