EP1770333B1 - Anti-coking injector arm - Google Patents

Anti-coking injector arm Download PDF

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Publication number
EP1770333B1
EP1770333B1 EP06121357A EP06121357A EP1770333B1 EP 1770333 B1 EP1770333 B1 EP 1770333B1 EP 06121357 A EP06121357 A EP 06121357A EP 06121357 A EP06121357 A EP 06121357A EP 1770333 B1 EP1770333 B1 EP 1770333B1
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EP
European Patent Office
Prior art keywords
fuel
distributor
central
duct
injection system
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EP06121357A
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German (de)
French (fr)
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EP1770333A1 (en
Inventor
Didier Hernandez
Thomas Noel
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Safran Aircraft Engines SAS
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SNECMA SAS
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
    • F23D11/24—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space by pressurisation of the fuel before a nozzle through which it is sprayed by a substantial pressure reduction into a space
    • F23D11/26—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space by pressurisation of the fuel before a nozzle through which it is sprayed by a substantial pressure reduction into a space with provision for varying the rate at which the fuel is sprayed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
    • F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
    • F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D2900/00—Special features of, or arrangements for burners using fluid fuels or solid fuels suspended in a carrier gas
    • F23D2900/00016—Preventing or reducing deposit build-up on burner parts, e.g. from carbon
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K2900/00—Special features of, or arrangements for fuel supplies
    • F23K2900/05003—Non-continuous fluid fuel supply

Definitions

  • the invention relates to a fuel injector fitted to the combustion chamber of a gas turbine engine, more particularly in an aircraft turbojet engine. It relates in particular to an improvement to avoid fuel coking in the arm of the injector where are formed two coaxial ducts belonging to different fuel supply circuits, respectively a primary circuit and a secondary circuit.
  • the combustion chamber is provided with a plurality of injectors regularly distributed circumferentially at the bottom of the annular combustion chamber.
  • Each injector comprises a curved arm terminated by a spray head.
  • the fuel flows in this arm, attached to the outer casing surrounding the combustion chamber, to the spray head.
  • Compressed air from a high pressure compressor circulates in this housing. The fuel is mixed with the air in the bottom of the combustion chamber before igniting in it.
  • the so-called primary circuit or idle circuit is designed to obtain a particularly fine spraying of the fuel. Its flow is limited but permanent.
  • the so-called secondary circuit or full-gas circuit is designed to complete the fuel flow to the full-throttle point allowing, in particular, to achieve all the power required for take-off.
  • this secondary circuit is not used continuously and its flow is sometimes very low at certain speeds.
  • the fuel from these two circuits reaches the spray head by flowing in coaxial conduits defined within the arm.
  • the central duct belongs to the primary circuit and the tubular duct that surrounds it belongs to the secondary circuit.
  • most of the injector, including the arm can be subjected to high temperatures (300 ° K to 950 ° K for a full throttle) since such an arm is installed in a hot air stream from the last stage of the high pressure compressor.
  • the secondary circuit may not be used or have a very low flow rate, as mentioned above.
  • a conventional dual circuit mechanical injector has a reinforced thermal insulation around the arm of the injector.
  • Such an arm is therefore complex and expensive to manufacture and its mass is increased by the thermal insulation elements.
  • the document WO03 / 054447A discloses a gas turbine fuel system dual fuel injection system, in which the fuel line of a fuel system crosses in the injector spray head the conduit of an additional combustion air circuit. This additional air flows in an annular peripheral duct from the injector to the head to cool the injector per se. Coking of the fuel is avoided only in the event that only one fuel circuit is in use.
  • the invention proposes a novel design of a gas turbine two-circuit fuel injection system according to claim 1, which makes it possible to eliminate or at least considerably reduce the static thermal insulation in favor of cooling by the circulation of the fuel itself.
  • Said spray head may comprise a splitter connected to the ends of the two ducts defined in the arm.
  • This distributor is housed in a spray nozzle extending said arm and said channel arrangement is formed essentially in said distributor.
  • the central duct is extended by an axial blind hole of said distributor and bores extend between said blind hole and respective grooves made, for example longitudinally, to the surface of said distributor.
  • These grooves form, with the inner surface of the nozzle, outer channels opening into an open annular cavity defined at the free end of this nozzle.
  • a nozzle extending said distributor inside said nozzle externally comprises substantially helical ribs and in contact with the inner wall of the nozzle.
  • the nozzle defines with said inner wall of the nozzle rotational channels arranged between the outer channels of the distributor and the annular cavity. The rotation of the fuel makes it possible to obtain a divergent jet.
  • the nozzle is hollowed to define with the end of said distributor, a cavity central having a central orifice for spraying the fuel.
  • the peripheral duct defined in the arm communicates with holes made in the distributor and opening into this central cavity. These bores extend at least partly obliquely to an axis of the distributor, to cause a rotation of the fuel in the central cavity and therefore a divergent ejection of the spray of fuel sprayed.
  • the figure 1 is partially in half section, a combustion chamber 11 of an aircraft turbojet engine 10.
  • the chamber of generally annular geometry combustion comprises a chamber bottom 12 inside which are engaged the spray heads 14 of a number of injectors 15 carried by a casing 16 surrounding the combustion chamber.
  • the injectors 15 are spaced regularly circumferentially.
  • Air under relatively hot pressure from an upstream high pressure compressor is introduced into the housing by an annular diffuser 18.
  • the hot air is divided into two streams; one passes through the housing 16 bypassing the combustion chamber 11 and the other engages in the combustion chamber through holes in the chamber bottom 12, to mix with the fuel projected by the spray heads 14 in the chamber of combustion.
  • the fuel ignites to provide gas supplying a downstream high pressure turbine.
  • Each injector 15 comprises an injector arm 22 with two coaxial ducts, supporting and supplying the spray head 14 which is of the double jet type.
  • the arm 22 is bent to maintain the spray head perpendicular to the chamber bottom.
  • the structure of the arm is very simple. It comprises an outer tube 24 surrounded by a protective casing 25 and an inner tube 26 engaged co-axially in the outer tube so as to define two coaxial ducts, a central duct 28 delimited by said inner tube and a sectional duct 29 with section annular surrounding the central duct and defined by the two tubes 24, 26 inside and outside.
  • the injector arm is installed in a stream of relatively hot compressed air, that is to say, the air which bypasses the combustion chamber 11 and partly the air entering the combustion chamber.
  • each injector 15 is connected to two fuel supply circuits for adapting the supply conditions to different engine speeds.
  • the two circuits, outside the housing 16 are symbolized in broken lines.
  • the peripheral duct 29 is part of the so-called primary fuel circuit 32 while the central duct 28 is part of the so-called secondary fuel circuit 33.
  • the fuel circulating in the peripheral duct (at a temperature much lower than that of the air circulating in the crankcase) does not have time to coke due to a flow rate sufficient and is on the other hand an effective thermal protection for the fuel that is in the central conduit 28.
  • the fuel flowing in the peripheral duct continuously cools the inner tube 26 and prevents the heating of fuel that stagnates eventually, at certain times, in the central duct. Therefore, the coking of the fuel in the central duct is avoided.
  • the spray head comprises an arrangement of channels for ejecting the circulating fuel in said central duct 28 in a divergent jet located outside the fuel jet coming from the peripheral duct 29.
  • the spray head 14 comprises, at the end of the arm 22: a distributor 35, a nozzle 37 extending said distributor and a nozzle 39 connected to the end of the arm 22 and surrounding the distributor and the nozzle.
  • the distributor 35 is connected to the ends of the two ducts 28, 29. It is approximately cylindrical and has an axis xx which merges with the axis of the divergent double jet produced by the spray head 14.
  • the above-mentioned channel arrangement is provided essentially in this distributor.
  • the central duct 28 is extended by a blind hole 39 of said axial distributor. Holes 41 perpendicular to the blind hole (here four holes at 90 ° relative to each other) extend between the blind hole and respective grooves 42 made here, longitudinally, to the surface of the distributor.
  • the grooves 42 form with the inner surface of this nozzle outer channels 43 opening into an open annular cavity 45 defined at the free end of the nozzle. It comprises a conical orifice 47 which delimits the outer contour of the outlet of said open annular cavity 45.
  • This annular cavity is internally limited by the outer surface, here conical, of the nozzle 37. This extends the distributor 35 to the inside of the nozzle and it has externally substantially helical ribs 60 themselves in contact with the inner wall of the nozzle 39. They therefore define with them rotating channels which are arranged between the channels. 43 and the annular cavity 45.
  • the fuel supplied by the central duct 28 passes through the blind hole 39, then into the holes 41 and into the outer channels before engaging in the rotation channels. This gives a divergent jet which surrounds the jet from the peripheral duct.
  • the nozzle 37 is hollowed to define, with the end of the distributor 35, a central cavity 50 opening axially through a central orifice 52 for spraying the fuel of the primary circuit.
  • the annular cavity 45 opens all around this central orifice 52.
  • the peripheral duct 29 communicates with holes 55 formed in the distributor and opening into this central cavity 50. As shown, these bores extend at first substantially longitudinally, that is to say, parallel to the axis and then obliquely relative to this axis to generate a rotation of the fuel in the central cavity. In this way, the spray that emerges from the central orifice 52 is divergent.
  • the invention relates primarily to the anti-coking arrangement.
  • Such a structure can be used with other types of spray heads designed to be powered by a primary circuit and a secondary circuit as defined above.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)

Description

L'invention se rapporte à un injecteur de carburant équipant la chambre de combustion d'un moteur de turbine à gaz, plus particulièrement dans un turboréacteur d'avion. Elle concerne notamment un perfectionnement permettant d'éviter la cokéfaction du carburant dans le bras de l'injecteur où sont ménagés deux conduits coaxiaux appartenant à des circuits d'alimentation de carburant différents, respectivement un circuit primaire et un circuit secondaire.The invention relates to a fuel injector fitted to the combustion chamber of a gas turbine engine, more particularly in an aircraft turbojet engine. It relates in particular to an improvement to avoid fuel coking in the arm of the injector where are formed two coaxial ducts belonging to different fuel supply circuits, respectively a primary circuit and a secondary circuit.

Dans un turboréacteur d'avion, la chambre de combustion est pourvue d'une pluralité d'injecteurs régulièrement répartis circonférentiellement au fond de la chambre de combustion annulaire. Chaque injecteur comporte un bras courbe terminé par une tête de pulvérisation. Le carburant circule dans ce bras, fixé au carter extérieur entourant la chambre de combustion, jusqu'à la tête de pulvérisation. L'air comprimé provenant d'un compresseur haute pression circule dans ce carter. Le carburant est mélangé à l'air dans le fond de la chambre de combustion avant de s'enflammer dans celle-ci.In an aircraft turbojet engine, the combustion chamber is provided with a plurality of injectors regularly distributed circumferentially at the bottom of the annular combustion chamber. Each injector comprises a curved arm terminated by a spray head. The fuel flows in this arm, attached to the outer casing surrounding the combustion chamber, to the spray head. Compressed air from a high pressure compressor circulates in this housing. The fuel is mixed with the air in the bottom of the combustion chamber before igniting in it.

Pour garantir une pulvérisation optimale du carburant dans le document US5570580A , qui représente l'art antérieur le plus proche de l'invention, propose toutes les conditions de fonctionnement du moteur, des injecteurs mécaniques à deux circuits de carburant. Habituellement, les deux circuits de carburant de ce type d'injecteur sont appelés respectivement circuit primaire et circuit secondaire.To ensure optimum fuel spraying in the document US5570580A , which represents the closest prior art of the invention, proposes all the operating conditions of the engine, mechanical injectors with two fuel circuits. Usually, the two fuel circuits of this type of injector are called respectively primary circuit and secondary circuit.

Le circuit dit primaire ou circuit de ralenti est conçu pour obtenir une pulvérisation particulièrement fine du carburant. Son débit est limité mais permanent.The so-called primary circuit or idle circuit is designed to obtain a particularly fine spraying of the fuel. Its flow is limited but permanent.

Le circuit dit secondaire ou circuit plein gaz est conçu pour compléter le débit de carburant jusqu'au point de plein gaz permettant, notamment, d'atteindre toute la puissance nécessaire au décollage. En revanche, ce circuit secondaire n'est pas utilisé en permanence et son débit est parfois très faible à certains régimes.The so-called secondary circuit or full-gas circuit is designed to complete the fuel flow to the full-throttle point allowing, in particular, to achieve all the power required for take-off. On the other hand, this secondary circuit is not used continuously and its flow is sometimes very low at certain speeds.

Le carburant de ces deux circuits parvient à la tête de pulvérisation en s'écoulant dans des conduits coaxiaux définis à l'intérieur du bras.The fuel from these two circuits reaches the spray head by flowing in coaxial conduits defined within the arm.

Classiquement, le conduit central appartient au circuit primaire et le conduit tubulaire qui l'entoure appartient au circuit secondaire. Or, la plus grande partie de l'injecteur, notamment le bras, peut être soumis à des températures élevées (300°K à 950°K pour un régime plein gaz) puisqu'un tel bras est installé dans un flux d'air chaud provenant du dernier étage du compresseur haute pression. De plus, pendant certaines phases de fonctionnement où la température de l'air issu du compresseur est relativement élevée (430 à 600°K), le circuit secondaire peut ne pas être utilisé ou présenter un débit très faible, comme mentionné ci-dessus.Conventionally, the central duct belongs to the primary circuit and the tubular duct that surrounds it belongs to the secondary circuit. However, most of the injector, including the arm, can be subjected to high temperatures (300 ° K to 950 ° K for a full throttle) since such an arm is installed in a hot air stream from the last stage of the high pressure compressor. In addition, during certain operating phases where the temperature of the air coming from the compressor is relatively high (430 to 600 ° K), the secondary circuit may not be used or have a very low flow rate, as mentioned above.

Il pourrait en résulter un gommage ou une cokéfaction du carburant stagnant à l'intérieur de la partie du circuit secondaire qui s'étend dans le bras, c'est-à-dire le conduit tubulaire extérieur.This could result in scrubbing or coking of the stagnant fuel within the portion of the secondary circuit that extends into the arm, i.e., the outer tubular conduit.

Ces phénomènes peuvent altérer les caractéristiques des injecteurs, pouvant aller jusqu'au bouchage de certains d'entre eux et entraînant donc une carburation non homogène dans la chambre de combustion ainsi qu'une distorsion de la carte des températures à l'intérieur de celle-ci. Il peut en résulter une perte de performances de la chambre de combustion et de la turbine. Ces problèmes peuvent provoquer des brûlures du distributeur haute pression, de la turbine haute pression et même de certains éléments constitutifs de la turbine basse pression.These phenomena can alter the characteristics of the injectors, which can go as far as blocking some of them and thus leading to inhomogeneous carburization in the combustion chamber as well as a distortion of the temperature map inside this chamber. this. This can result in a loss of performance of the combustion chamber and the turbine. These problems can cause burns of the high pressure distributor, the high pressure turbine and even some components of the low pressure turbine.

Pour éviter les phénomènes de cokéfaction, un injecteur mécanique double circuit classique comporte une isolation thermique renforcée autour du bras de l'injecteur. Un tel bras est donc complexe et coûteux à fabriquer et sa masse est augmentée par les éléments d'isolation thermique.To avoid coking phenomena, a conventional dual circuit mechanical injector has a reinforced thermal insulation around the arm of the injector. Such an arm is therefore complex and expensive to manufacture and its mass is increased by the thermal insulation elements.

Le document WO03/054447A décrit un système d'injection à deux circuits de carburant de turbine à gaz, dans lequel le conduit d'un circuit de carburant croise dans la tête de pulvérisation de l'injecteur le conduit d'un circuit additionnel d'air de combustion. Cet air additionnel s'écoule dans un conduit périphérique annulaire de l'injecteur jusqu'à la tête pour refroidir l'injecteur en soi. La cokéfaction du carburant est évitée seulement au cas où un seul circuit der carburant est en service.The document WO03 / 054447A discloses a gas turbine fuel system dual fuel injection system, in which the fuel line of a fuel system crosses in the injector spray head the conduit of an additional combustion air circuit. This additional air flows in an annular peripheral duct from the injector to the head to cool the injector per se. Coking of the fuel is avoided only in the event that only one fuel circuit is in use.

L'invention propose une nouvelle conception d'un système d'injection à deux circuits de carburant dans un turbine à gaz selon la revendication 1, permettant de supprimer ou au moins de considérablement réduire l'isolation thermique statique au profit d'un refroidissement par la circulation du carburant lui-même.The invention proposes a novel design of a gas turbine two-circuit fuel injection system according to claim 1, which makes it possible to eliminate or at least considerably reduce the static thermal insulation in favor of cooling by the circulation of the fuel itself.

En effet, puisque le carburant circule en permanence dans le circuit primaire dudit système d'injection, le fait de le faire circuler autour du conduit central dans lequel circule dorénavant le carburant du circuit secondaire dudit système d'injection permet d'éviter la cokéfaction dans ce conduit lorsque le carburant y stagne ou y circule avec un très faible débit. Le carburant du circuit primaire, introduit à une température beaucoup plus basse que celle de l'air provenant du compresseur haute pression, ne peut faire l'objet d'une cokéfaction (puisqu'il circule en permanence) et permet de refroidir le carburant du circuit secondaire lorsque celui-ci stagne dans le conduit central.Indeed, since the fuel is continuously circulating in the primary circuit of said injection system, circulating it around the central duct in which the fuel of the secondary circuit of said injection system now flows. prevents coking in this duct when the fuel stagnates there or circulates at a very low flow rate. The fuel of the primary circuit, introduced at a temperature much lower than that of the air coming from the high-pressure compressor, can not be coked (since it circulates continuously) and makes it possible to cool the fuel of the secondary circuit when it stagnates in the central conduit.

Comme mentionné précédemment, il est souhaitable de pulvériser le carburant provenant du circuit primaire au centre du jet divergent délivré par l'injecteur et le carburant issu du circuit secondaire à la périphérie du jet pulvérisé.As mentioned previously, it is desirable to spray the fuel from the primary circuit at the center of the diverging jet delivered by the injector and the fuel from the secondary circuit at the periphery of the spray.

Ladite tête de pulvérisation peut comporter un répartiteur connecté aux extrémités des deux conduits définis dans le bras. Ce répartiteur est logé dans un embout de pulvérisation prolongeant ledit bras et ledit agencement de canaux est ménagé essentiellement dans ledit répartiteur.Said spray head may comprise a splitter connected to the ends of the two ducts defined in the arm. This distributor is housed in a spray nozzle extending said arm and said channel arrangement is formed essentially in said distributor.

Par exemple, le conduit central est prolongé par un trou borgne axial dudit répartiteur et des perçages s'étendent entre ledit trou borgne et des rainures respectives pratiquées, par exemple longitudinalement, à la surface dudit répartiteur. Ces rainures forment, avec la surface intérieure de l'embout, des canaux extérieurs débouchant dans une cavité annulaire ouverte définie à l'extrémité libre de cet embout.For example, the central duct is extended by an axial blind hole of said distributor and bores extend between said blind hole and respective grooves made, for example longitudinally, to the surface of said distributor. These grooves form, with the inner surface of the nozzle, outer channels opening into an open annular cavity defined at the free end of this nozzle.

Par exemple, une buse prolongeant ledit répartiteur à l'intérieur dudit embout comporte extérieurement des nervures sensiblement hélicoïdales et en contact avec la paroi intérieure de l'embout. Ainsi, la buse définit avec ladite paroi intérieure de l'embout des canaux de mise en rotation agencés entre les canaux extérieurs du distributeur et la cavité annulaire. La mise en rotation du carburant permet d'obtenir un jet divergent.For example, a nozzle extending said distributor inside said nozzle externally comprises substantially helical ribs and in contact with the inner wall of the nozzle. Thus, the nozzle defines with said inner wall of the nozzle rotational channels arranged between the outer channels of the distributor and the annular cavity. The rotation of the fuel makes it possible to obtain a divergent jet.

Pour ce qui concerne le carburant du circuit primaire, la buse est creusée pour définir avec l'extrémité dudit répartiteur, une cavité centrale comportant un orifice central pour la pulvérisation du carburant. Le conduit périphérique défini dans le bras communique avec des perçages pratiqués dans le répartiteur et débouchant dans cette cavité centrale. Ces perçages s'étendent au moins en partie en biais par rapport à un axe du répartiteur, pour engendrer une mise en rotation du carburant dans la cavité centrale et par conséquent une éjection divergente du jet de carburant pulvérisé.With regard to the fuel of the primary circuit, the nozzle is hollowed to define with the end of said distributor, a cavity central having a central orifice for spraying the fuel. The peripheral duct defined in the arm communicates with holes made in the distributor and opening into this central cavity. These bores extend at least partly obliquely to an axis of the distributor, to cause a rotation of the fuel in the central cavity and therefore a divergent ejection of the spray of fuel sprayed.

L'invention sera mieux comprise et d'autres avantages de celle-ci apparaîtront plus clairement à la lumière de la description qui va suivre d'un injecteur conforme à son principe, donnée uniquement à titre d'exemple et faite en référence aux dessins annexés dans lesquels :

  • la figure 1 est une vue schématique en coupe de la chambre de combustion, montrant l'un des injecteurs conformes à l'invention ;
  • la figure 2 est une vue en perspective éclatée de l'extrémité de l'injecteur ;
  • la figure 3 est une vue en perspective de la partie terminale de l'injecteur, selon une coupe III III de la figure 2 ;
  • la figure 4 est une vue en perspective, de la même partie terminale de l'injecteur, selon une coupe IV IV de la figure 2.
The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an injector according to its principle, given solely by way of example and with reference to the accompanying drawings. wherein :
  • the figure 1 is a schematic sectional view of the combustion chamber, showing one of the injectors according to the invention;
  • the figure 2 is an exploded perspective view of the end of the injector;
  • the figure 3 is a perspective view of the end portion of the injector, according to a section III III of the figure 2 ;
  • the figure 4 is a perspective view, of the same end portion of the injector, according to a section IV IV of the figure 2 .

La figure 1 représente partiellement en demi coupe, une chambre de combustion 11 d'un turboréacteur d'avion 10. La chambre de combustion à géométrie globalement annulaire comporte un fond de chambre 12 à l'intérieur duquel sont engagées les têtes de pulvérisation 14 d'un certain nombre d'injecteurs 15 portés par un carter 16 entourant la chambre de combustion. Les injecteurs 15 sont espacés régulièrement circonférentiellement. De l'air sous pression relativement chaud, provenant d'un compresseur haute pression situé en amont, est introduit dans le carter par un diffuseur annulaire 18. L'air chaud se partage en deux flux ; l'un traverse le carter 16 en contournant la chambre de combustion 11 et l'autre s'engage dans la chambre de combustion par des orifices du fond de chambre 12, pour se mélanger au carburant projeté par les têtes de pulvérisation 14 dans la chambre de combustion. Le carburant s'enflamme pour fournir des gaz alimentant une turbine haute pression 20 située en aval.The figure 1 is partially in half section, a combustion chamber 11 of an aircraft turbojet engine 10. The chamber of generally annular geometry combustion comprises a chamber bottom 12 inside which are engaged the spray heads 14 of a number of injectors 15 carried by a casing 16 surrounding the combustion chamber. The injectors 15 are spaced regularly circumferentially. Air under relatively hot pressure from an upstream high pressure compressor is introduced into the housing by an annular diffuser 18. The hot air is divided into two streams; one passes through the housing 16 bypassing the combustion chamber 11 and the other engages in the combustion chamber through holes in the chamber bottom 12, to mix with the fuel projected by the spray heads 14 in the chamber of combustion. The fuel ignites to provide gas supplying a downstream high pressure turbine.

Chaque injecteur 15 comporte un bras d'injecteur 22 à deux conduits coaxiaux, supportant et alimentant la tête de pulvérisation 14 qui est du type à double jet. Le bras 22 est coudé à façon à maintenir la tête de pulvérisation perpendiculaire au fond de chambre. La structure du bras est des plus simples. Il comporte un tube extérieur 24 entouré d'une enveloppe protectrice 25 et un tube intérieur 26 engagé co-axialement dans le tube extérieur de façon à définir deux conduits coaxiaux, un conduit central 28 délimité par ledit tube intérieur et un conduit périphérique 29 à section annulaire entourant le conduit central et délimité par les deux tubes 24, 26 intérieur et extérieur. Comme on le voit sur la figure 1, le bras d'injecteur est installé dans une veine d'air comprimé relativement chaud, à savoir pour partie l'air qui contourne extérieurement la chambre de combustion 11 et pour partie l'air qui pénètre dans cette chambre de combustion.Each injector 15 comprises an injector arm 22 with two coaxial ducts, supporting and supplying the spray head 14 which is of the double jet type. The arm 22 is bent to maintain the spray head perpendicular to the chamber bottom. The structure of the arm is very simple. It comprises an outer tube 24 surrounded by a protective casing 25 and an inner tube 26 engaged co-axially in the outer tube so as to define two coaxial ducts, a central duct 28 delimited by said inner tube and a sectional duct 29 with section annular surrounding the central duct and defined by the two tubes 24, 26 inside and outside. As we see on the figure 1 , the injector arm is installed in a stream of relatively hot compressed air, that is to say, the air which bypasses the combustion chamber 11 and partly the air entering the combustion chamber.

D'autre part, comme mentionné précédemment, chaque injecteur 15 est relié à deux circuits d'alimentation de carburant permettant d'adapter les conditions d'alimentation aux différents régimes du moteur. Les deux circuits, à l'extérieur du carter 16 sont symbolisés en traits interrompus. On distingue un circuit de carburant 32 dit primaire ou circuit de ralenti dont le débit, quoique faible, est permanent, quelles que soient les conditions de fonctionnement du moteur et un circuit de carburant 33 dit secondaire à débit essentiellement variable mais pouvant dans certaines phases de fonctionnement être très faible voire presque nul.On the other hand, as mentioned above, each injector 15 is connected to two fuel supply circuits for adapting the supply conditions to different engine speeds. The two circuits, outside the housing 16 are symbolized in broken lines. There is a fuel circuit 32 said primary or idle circuit whose flow, although low, is permanent, regardless of the engine operating conditions and a fuel circuit 33 called secondary flow rate substantially variable but may in certain operating phases, be very low or almost zero.

Selon une caractéristique importante de l'invention, le conduit périphérique 29 fait partie du circuit de carburant 32 dit primaire tandis que le conduit central 28 fait partie du circuit de carburant 33 dit secondaire. Ainsi, pour les raisons indiquées plus haut, le carburant qui circule dans le conduit périphérique (à une température très inférieure à celle de l'air qui circule dans le carter) n'a pas le temps de se cokéfier du fait d'un débit suffisant et constitue d'autre part une protection thermique efficace pour le carburant qui se trouve dans le conduit central 28. En effet, le carburant circulant dans le conduit périphérique refroidit en permanence le tube intérieur 26 et empêche le réchauffement du carburant qui stagne éventuellement, à certains moments, dans le conduit central. Par conséquent, la cokéfaction du carburant dans le conduit central est évitée.According to an important characteristic of the invention, the peripheral duct 29 is part of the so-called primary fuel circuit 32 while the central duct 28 is part of the so-called secondary fuel circuit 33. Thus, for the reasons indicated above, the fuel circulating in the peripheral duct (at a temperature much lower than that of the air circulating in the crankcase) does not have time to coke due to a flow rate sufficient and is on the other hand an effective thermal protection for the fuel that is in the central conduit 28. In fact, the fuel flowing in the peripheral duct continuously cools the inner tube 26 and prevents the heating of fuel that stagnates eventually, at certain times, in the central duct. Therefore, the coking of the fuel in the central duct is avoided.

De ce fait, tous les systèmes d'isolation coûteux et compliqués qui étaient prévus dans un système d'injection classique, ont pu être supprimés.As a result, all expensive and complicated isolation systems that were provided in a conventional injection system could be eliminated.

Dans un injecteur double débit classique, on souhaite que le jet de carburant provenant du circuit secondaire 33 enveloppe le jet de carburant provenant du circuit primaire 32. Pour ce faire, la tête de pulvérisation comporte un agencement de canaux permettant d'éjecter le carburant circulant dans ledit conduit central 28 en un jet divergent situé à l'extérieur du jet de carburant issu du conduit périphérique 29.In a conventional dual flow injector, it is desired that the jet of fuel from the secondary circuit 33 envelops the jet of fuel from the primary circuit 32. To do this, the spray head comprises an arrangement of channels for ejecting the circulating fuel in said central duct 28 in a divergent jet located outside the fuel jet coming from the peripheral duct 29.

Comme on le voit sur les figures, la tête de pulvérisation 14 comporte, à l'extrémité du bras 22 : un répartiteur 35, une buse 37 prolongeant ledit répartiteur et un embout 39 raccordé à l'extrémité du bras 22 et entourant le répartiteur et la buse.As seen in the figures, the spray head 14 comprises, at the end of the arm 22: a distributor 35, a nozzle 37 extending said distributor and a nozzle 39 connected to the end of the arm 22 and surrounding the distributor and the nozzle.

Le répartiteur 35 est connecté aux extrémités des deux conduits 28, 29. Il est approximativement cylindrique et admet un axe x-x qui se confond avec l'axe du double jet divergent qui est produit par la tête de pulvérisation 14. L'agencement de canaux précité est ménagé essentiellement dans ce répartiteur.The distributor 35 is connected to the ends of the two ducts 28, 29. It is approximately cylindrical and has an axis xx which merges with the axis of the divergent double jet produced by the spray head 14. The above-mentioned channel arrangement is provided essentially in this distributor.

Ainsi, le conduit central 28 est prolongé par un trou borgne 39 axial dudit répartiteur. Des perçages 41 perpendiculaires au trou borgne (ici quatre perçages à 90° les uns par rapport aux autres) s'étendent entre le trou borgne et des rainures 42 respectives pratiquées, ici longitudinalement, à la surface du répartiteur. Comme l'embout 39 est ajusté sur le répartiteur, les rainures 42 forment avec la surface intérieure de cet embout des canaux extérieurs 43 débouchant dans une cavité annulaire ouverte 45 définie à l'extrémité libre de l'embout. Celui-ci comporte un orifice conique 47 qui délimite le contour extérieur de la sortie de ladite cavité annulaire ouverte 45. Cette cavité annulaire est limitée intérieurement par la surface extérieure, ici conique, de la buse 37. Celle-ci prolonge le répartiteur 35 à l'intérieur de l'embout et elle comporte extérieurement des nervures 60 sensiblement hélicoïdales elles-mêmes en contact avec la paroi intérieure de l'embout 39. Elles définissent donc avec celles-ci des canaux de mise en rotation qui sont agencés entre les canaux extérieurs 43 et la cavité annulaire 45.Thus, the central duct 28 is extended by a blind hole 39 of said axial distributor. Holes 41 perpendicular to the blind hole (here four holes at 90 ° relative to each other) extend between the blind hole and respective grooves 42 made here, longitudinally, to the surface of the distributor. As the nozzle 39 is fitted on the distributor, the grooves 42 form with the inner surface of this nozzle outer channels 43 opening into an open annular cavity 45 defined at the free end of the nozzle. It comprises a conical orifice 47 which delimits the outer contour of the outlet of said open annular cavity 45. This annular cavity is internally limited by the outer surface, here conical, of the nozzle 37. This extends the distributor 35 to the inside of the nozzle and it has externally substantially helical ribs 60 themselves in contact with the inner wall of the nozzle 39. They therefore define with them rotating channels which are arranged between the channels. 43 and the annular cavity 45.

Ainsi, le carburant amené par le conduit central 28 passe par le trou borgne 39, puis dans les perçages 41 et dans les canaux extérieurs avant de s'engager dans les canaux de mise en rotation. On obtient ainsi un jet divergent qui entoure le jet issu du conduit périphérique.Thus, the fuel supplied by the central duct 28 passes through the blind hole 39, then into the holes 41 and into the outer channels before engaging in the rotation channels. This gives a divergent jet which surrounds the jet from the peripheral duct.

La buse 37 est creusée pour définir, avec l'extrémité du répartiteur 35, une cavité centrale 50 débouchant axialement par un orifice central 52 pour la pulvérisation du carburant du circuit primaire. Ainsi, la cavité annulaire 45 débouche tout autour de cet orifice central 52. Le conduit périphérique 29 communique avec des perçages 55 pratiqués dans le répartiteur et débouchant dans cette cavité centrale 50. Comme représenté, ces perçages s'étendent d'abord sensiblement longitudinalement, c'est-à-dire parallèlement à l'axe puis en biais par rapport à cet axe pour engendrer une mise en rotation du carburant dans la cavité centrale. De cette façon, le jet pulvérisé qui ressort de l'orifice central 52 est divergent.The nozzle 37 is hollowed to define, with the end of the distributor 35, a central cavity 50 opening axially through a central orifice 52 for spraying the fuel of the primary circuit. Thus, the annular cavity 45 opens all around this central orifice 52. The peripheral duct 29 communicates with holes 55 formed in the distributor and opening into this central cavity 50. As shown, these bores extend at first substantially longitudinally, that is to say, parallel to the axis and then obliquely relative to this axis to generate a rotation of the fuel in the central cavity. In this way, the spray that emerges from the central orifice 52 is divergent.

L'invention concerne en premier lieu l'agencement anti-cokéfaction . Une telle structure peut être utilisée avec d'autres types de tête de pulvérisation conçus pour être alimentées par un circuit primaire et un circuit secondaire tels que définis ci-dessus.The invention relates primarily to the anti-coking arrangement. Such a structure can be used with other types of spray heads designed to be powered by a primary circuit and a secondary circuit as defined above.

Claims (7)

  1. An injection system having two fuel circuits for injecting fuel into a combustion chamber of a gas turbine engine, said system comprising a so-called "primary" fuel circuit (32) that delivers fuel continuously, a so-called "secondary" fuel circuit (33) that delivers fuel at an essentially variable rate, and an injector arm (22) having two ducts (28, 29) that are coaxial and that support and feed a two-jet spray head (14), the ducts comprising respectively a central duct (28) and a peripheral duct (29) of annular section surrounding said central duct, said injector arm being installed in a stream of compressed air that is relatively hot, the system being characterized in that said peripheral duct (29) is connected to the so-called "primary" fuel circuit (32) while said central duct (28) is connected to the so-called "secondary" fuel circuit (33), and in that said spray head (14) includes an arrangement of channels enabling the fuel flowing in said central duct to be ejected as a diverging jet situated outside the jet of fuel flowing in said peripheral duct.
  2. An injection system according to claim 8, characterized in that said spray head (14) includes a distributor (35) connected to the ends of the two ducts (28, 29) and housed in a spray endpiece (38) extending said arm, and in that said arrangement of channels is formed essentially in said distributor.
  3. An injection system according to claim 2, characterized in that said central duct (28) is extended by a blind hole (39) in said distributor, in that bores (41) extend between said blind hole and respective grooves (42) formed in the surface of said distributor, and in that the grooves co-operate with the inside surface of said endpiece to form outer channels (43) opening out into an open annular cavity (45) defined at the free end of said endpiece.
  4. An injection system according to claim 3, characterized in that it includes a nozzle (37) extending said distributor inside said endpiece (39), said open cavity (45) being defined between said nozzle and the inside wall of said endpiece, in that said nozzle is hollowed out to co-operate with the end of said distributor to define a central cavity (50), and in that said peripheral duct (29) communicates with bores (55) formed in said distributor and opening out into said central cavity, which includes a central orifice (52) for ejecting fuel from said primary circuit, said annular cavity (45) opening out all around said central orifice in order to spray fuel from said secondary circuit.
  5. An injection system according to claim 4, characterized in that the bores (55) extend at least in part at an angle relative to the axis of said distributor in order to cause the fuel in said central cavity (50) to swirl.
  6. An injection system according to claim 4, characterized in that said nozzle has external ribs (60) that are substantially helical and in contact with the inside wall of said endpiece in order to co-operate therewith to define swirling channels arranged between said outer channels (43) and said annular cavity (45).
  7. An injection system according to any one of claims 1 to 16, characterized in that said central duct (28) and said peripheral duct (29) are defined by coaxial tubes (24, 26).
EP06121357A 2005-09-28 2006-09-27 Anti-coking injector arm Active EP1770333B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0509879A FR2891314B1 (en) 2005-09-28 2005-09-28 INJECTOR ARM ANTI-COKEFACTION.

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EP1770333A1 EP1770333A1 (en) 2007-04-04
EP1770333B1 true EP1770333B1 (en) 2010-07-21

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US (1) US20070068164A1 (en)
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JP (1) JP2007093200A (en)
CA (1) CA2561225A1 (en)
DE (1) DE602006015580D1 (en)
FR (1) FR2891314B1 (en)
RU (1) RU2006134688A (en)

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US8443608B2 (en) * 2008-02-26 2013-05-21 Delavan Inc Feed arm for a multiple circuit fuel injector
FR2927949B1 (en) * 2008-02-27 2010-03-26 Snecma TURBOMACHINE DIFFUSER COMPRISING SCREWED ANNULAR SAILS
BR112013028196B1 (en) * 2011-05-17 2021-06-22 Snecma ANNULAR COMBUSTION CHAMBER FOR A TURB MACHINE AND TURB MACHINE
FR2975466B1 (en) * 2011-05-17 2013-05-24 Snecma ANNULAR COMBUSTION CHAMBER FOR A TURBOMACHINE
BR112016003574B1 (en) 2013-08-20 2021-10-13 Snecma FUEL INJECTION SYSTEM, FUEL INJECTION METHOD, COMPUTER PROGRAM PRODUCT AND STORAGE MEDIA
FR3010139B1 (en) * 2013-09-04 2019-05-17 Safran Aircraft Engines DEVICE AND METHOD FOR ESTIMATING CLAMPS IN A FUEL INJECTION SYSTEM IN A COMBUSTION CHAMBER OF AN ENGINE
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FR2891314B1 (en) 2015-04-24
FR2891314A1 (en) 2007-03-30
DE602006015580D1 (en) 2010-09-02
US20070068164A1 (en) 2007-03-29
JP2007093200A (en) 2007-04-12
RU2006134688A (en) 2008-04-10
CA2561225A1 (en) 2007-03-28
EP1770333A1 (en) 2007-04-04

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