FR2505401A1 - IMPROVED ANNULAR COMBUSTION CHAMBER FOR A GAS TURBINE ENGINE - Google Patents

Abstract

THE INVENTION RELATES TO AN ANNULAR COMBUSTION CHAMBER FOR A GAS TURBINE ENGINE WHICH DECREASES DAMAGING EMISSIONS FROM THE ENGINE AT LOW OR HIGH SPEEDS. SEVERAL CORNER POTS 56 VERY OPEN TOWARDS DOWNSTREAM, EACH INCLUDING AN INJECTOR 58 SURROUNDED BY A TURBULENCE GENERATOR 60, EQUIPPED THE UPSTREAM WALL OF CHAMBER 32 AND GENERATE A STRONG VORTEX DOUBLE A, B OCCUPYING THE ENTIRE PRIMARY ZONE OF THE BEDROOM AND NOW THE AIR FLOW IN CONTACT WITH THE POTS. THE FUEL TENDING TO PASS THROUGH REFRIGERANT AIR CURRENTS 70, 72 IS RETURNED INTO THE VORTEX BY THE AIR ENTERING THROUGH ORIFICES 68, ENSURING THE SWEEPING OF THE ENTIRE INTERNAL SURFACE OF THE PRIMARY ZONE OF THE CHAMBER BY A CURRENT OF ' AIR PREVENTS THE ACCUMULATION OF CARBON AND KEEPING THE TEMPERATURE OF THE SURFACES TO BE COOLED AT MINIMUM.

Description

i

  the present invention relates to combustion chambers

  annular type for gas turbine engines

  and aims in particular to build a bedroom

  annular bustion reducing harmful engine emissions The entry into force of environmental pollution legislation, particularly in the United States of America, has caused gas turbine engine manufacturers to make considerable efforts to reduce harmful emissions from turbine engines

  gas These emissions consist of fuels

  rants incompletely burnt and by car- bon oxide

  bone usually generated at low powers

  the engine and by nitrous oxides

  ques and fumes generated at high engine operating powers Control of all these

  emissions by one and the same type of control chamber

  bustion has proven to be very difficult even with

  combustion chambers with multiple injection system

  This is due to the fact that the solution of the problem at low speeds tends to aggravate this problem at high speeds and vice versa. The present invention aims to provide a combustion chamber in which the emissions occurring at low powers and the fumes appearing at high speeds will be completely maltreated while the emission of nitric oxides will be at least partially. To achieve these objectives, the combustion chamber according to the present invention is based on very advanced control of the aerodynamic and thermodynamic processes taking place in the primary zone of the combustion chamber:

  the present invention provides a combustion chamber

  annular tion for a gas turbine engine, this chamber comprising an annular part defined by internal and external annular walls and by an upstream end wall, said internal walls and

  external having a plurality of openings allows

  both to the air entering said annular part,

  said upstream end wall having a plurali-

  tee of equidistant openings, a tapered pot to

  a gaping downstream base being fixed to said end wall.

  upstream tee coaxially to each of said openings thereof, the included angle of each pot being in the range from 309 to 90 e, a fuel injector

  and a turbulence generator being placed in the former

  upstream end of each pot, said tur-

  bulence being placed between the fuel injector and

  the wall of the pot, each turbulence generator

  bearing a plurality of curved blades which can

  deflect a draft of up to an angle

  652, at least part of the openings of said pa-

  internal and external annular kings being arranged so as to direct an air current on the downstream face of said upstream end wall

  The invention is described below in detail in detail.

  referring to some preferred, nonlimiting examples of embodiment shown in the accompanying drawings in which:

  Figure 1 is a longitudinal section of a turbo-

  ducted fan reactor, equipped with a

  annular combustion bre according to this in-

  vention; Figure 2 is a schematic longitudinal section on a larger scale of the combustion chamber of the turbojet engine of Figure 1; Figure 3 is a schematic longitudinal section, and on a much larger scale, of the upstream end of the combustion chamber of Figure 2;

  FIG. 4 is a view identical to that of FIG.

  gure 3 showing a variant of the invention; Figure 5 is a section similar to that of

  Figure 2, showing a second variant of the invention

  tion; Figure 6 is a view in the direction of the arrow A in Figure 5 Figure 7 is a detail view of the part of Figure 5 surrounded by a circle B;

  FIG. 8 is a longitudinal section of an injector

  air nebulized fuel burner, usable with the combustion chambers of Figures 3, 4 and, 6, 7; and Figure 9 is a section along line 9-9 of Figure 8 Figure 1 shows, in longitudinal section, a ducted fan turbojet 10 comprising a single front fan 12 driven by a low pressure turbine 14, a medium pressure compressor 16 driven by a medium pressure turbine 18, a high pressure compressor 20 driven by a

  high pressure turbine 22, and a switchgear

  bustion 24 The air set in motion by the blower 12 flows through a bypass duct 26 and escapes through a propellant nozzle 28 while the gases leaving the turbines 14, 18 and 22 escape through a second propellant nozzle 30 The combustion apparatus 24, shown more in

  detail in Figure 2, includes a com-

  annular bust 32 defined by an internal annular wall 34 and by an external annular wall 36, an upstream end wall 38, and, at its downstream end, a plurality of outlet guide vanes 40 - This combustion chamber is enclosed in an annular casing 42 constituted by an internal casing 44, an external casing 46, and, at its upstream end, by a cap 48 This annular casing 42 receives a stream of pressurized air coming from the high pressure compressor 20 and penetrating by a series of blades

  guide 50 and by a discharge diffuser 52-

  The upstream end wall 38 is pierced with a plura-

  a number of openings 54, equidistant and arranged in a circle

  conference, coaxially to each of which is mounted a pot 56, fixed to said upstream wall 38, and

  having an inclusive angle, 909 in principle, opens

  downstream A fuel injector 58 is

  mounted at the upstream end of each pot, and a gener-

  The air vortex generator 60 is inserted between the

  nozzle 58 and the pot 56 A cover in the shape of a semi-toroidal crown 62 closes the upstream end of the combustion chamber

  32; this cover is pierced with a plurality of openings

  tures 64 allowing the penetration of air into the primary zone of the combustion chamber and into the fuel injector, as well as the mounting of each injector in its respective pot Preferably, each injector will be of the nebulous type.

  air flow, in which a high air flow

  pressure and at high speed comes hit a one

  fuel flow in the form of a sheet or jet

  dividends to nebulize this fuel Figure 3 shows that the vortex generator

  of air 60 includes a blade whose vanes are

  curved so that the air flow can be deflected at an angle of about 652

  The inner wall 34 and the outer wall 36 are per-

  ducts 66 for the dilution air inlet,

  and inlet ports 68, 70 and 72 for the penetration of

  tion of air mainly intended for cooling

  walls of the combustion chamber These o-

  inlet ports 68, 70 and 72 are formed, essen-

  tially, by a plurality of very close holes

  each other, drilled at a specific angle

  mined to ensure the flow of refrigerant air in the required direction The incoming air stream

  through the orifices 68 assumes, in addition to its function of re-

  cooling of the upstream end wall 38, a

  flow regulating function, as described

  ra further N the individual characteristics of the device are established and assembled so as to produce the effects

  following: a powerful double occupant vortex essen-

  the entire volume of the primary zone of com-

  bustion, that is to say the enclosure located upstream of the conduits 66; a means of blocking the entrainment of fuel in the air stream for cooling the walls, essentially a sweep of all the

  metal surfaces by a rapid air stream er-

  fishing carbon buildup and diminishing bound-

  stretched surfaces to cool The powerful double vortex is generated by the pots 56, thanks to their wide angle included, and the adhesion of the current to the pots is ensured by the swirl generators 60 which can deflect this current by an angle of 602 or more The flow of air, drawn inwards, penetrating through the orifices 68, and which is perpendicular to the longitudinal axis of the combustion chamber, prevents the fuel contained

  in the double vortex to separate from it and be

  dragged in the refrigerant air streams adjacent to the walls 34 and 36 of the combustion chamber

  With regard to the surfaces of the

  bustion, the interior of the pots is swept by the air

  swirling out of turbulent generators

  lence 60, the upstream end wall 38 is scanned

  by the air penetrating through the orifices 68, and the pa-

  kings 34 and 36 are swept by the air penetrating by

orifices 70 and 72 -

  In addition to the production of the powerful double vortex sought-

  ché, the use of wide-angle pots 56 also has the advantage of reducing the extent of the surfaces to be cooled When the turbojet engine is running, the fuel reaches the injector 58 and the air passes through this injector 58, the blades of the turbulence generator 60, and the air inlet orifices 66, 68, 70 and 72 A current

  very energetic toroldal vortex, indicated by arrows

  ches A and B, originates in the primary zone of

  the combustion chamber under the action of the pots-

  very open gle 56 and turbulence vanes 60 A very rapid mixing of air and fuel occurs, even at low power speeds o, due to the relatively low pressure and speed of the air in the injector, the nebulizing effect of this air is reduced Any fuel tending

  to escape from the main current of the vortex to pass-

  ser in the cooling current of the walls is captured by the air flow entering through the orifices

  68 and maintained in the vortex Practically, the to-

  Fuel quality therefore takes part in the combustion process, in particular at low power, which reduces emissions of unburned hydrocarbons and carbon monoxide under these operating conditions.

  The aerodynamic and thermodynamic conditions in-

  gendrés in the primary area of the com-

  bustion also creates a richer mixture, both at low and high power regimes At low regimes, a richer mixture is tolerable due to the improvement in combustion efficiency while at high power regimes, this richer mixture tends to decrease NO emissions although smoke production may increase but not to an unacceptable level In the variant of the invention shown in Figure 4, each of the annular walls 34 and 36 of the combustion chamber has an annular cooling groove 74, of V-shaped cross section, each having an air inlet port 76 directed upstream and an air inlet port 78 directed downstream The air entering through these orifices is intended to cool the walls of the combustion chamber, but the air entering through the orifices 76 also serves to reinforce the air current passing through the orifices 68 to pocket the entrainment of the fuel. by the neck rant of refrigerant air Any fuel which mixes with the stream of refrigerant air hardly burns because the mixing rate and the temperature will be low

  Figure 8 shows a nebulized fuel injector

  air intake 58 comprising a body 80 and a nozzle 82 defining between them a venturi duct 84 terminating in a circular spraying orifice 86 This injector is mounted in the center of the crown of blades 60 of the turbulence generator and comprises a

  fuel distributor 88 communicating with the

  venturi line 84 through fuel inlet ports

  rant 90 perpendicular or oblique Preferably, the turbulence-generating vanes comprise a series of curved vanes, unlike

  with straight inclined blades, usually used

  smooth, subject to the stall of the air streams and to a partially empty operation of air when they deflect the latter by a wide angle, for example more than 452 As shown in FIG. 9, the blades of the generator turbulence are arranged to deflect the air at angles up to 652, each of them having an air inlet portion aligned with the direction of air arrival and going

  marry the remaining part of the dawn inclined to the an-

  gle desired air outlet Preferably, the

  exit ges constituted by the intervals separating

  the vanes 60 will be long enough for the air to leave

  as the turbulence generator does it at the desired angle and not at a lower angle Bn now referring to Figures 5, 6 and 7, in which the elements identical to those of the figures

  previous ones have the same figures, we see the ap-

  combustion lining 24, over its entire length,

  enclosed in the casing 92 of a two-neck motor

  packing lines 94 and 96 are placed, respectively

  between the internal wall 34 of the

  combustion and the internal casing 44 of the annular casing

  area 42, and between the outer wall 36 of said combustion chamber and the outer casing 46 of said

  crankcase These packing rings are used to

  monitor the speed of the air flowing between them and the walls of the combustion chamber

  The upstream end of the combustion chamber is im-

  mobilized by means of a series of 98 pins carried

  each by the corresponding injector 58 and engages

  giant in a bore made in a plate 100 fi-

attached to cover 62

  Figures 6 and 7 in particular show the fixing

  tion of the pots 56 to the upstream end wall 38 of the chamber, and to an annular heat shield made of contiguous segments 102 each pierced with a circular opening 104 corresponding to the diameter of the downstream part of the pot 56 corresponding

  The segments constituting the heat shield are ali-

  mented in refrigerant air through orifices 106 formed in a flange 56 a of each pot The refrigerant air enters a chamber 108 formed between the segment of the heat shield and the flange 56 a, and escapes through an annular gap 110 between this segment and the pot Although the included angle of each pot 56 should be

  preferably be around 902 to generate an in-

  energetic version of flow in the primary zone

  mayor of the combustion chamber and to decrease the surface of the upstream end wall 38, it may be necessary to reduce this angle to maintain

  this flow in contact with the pot in all circuits

  The service life of the components

  health can be increased in this way at the cost

  an increase in the area to be cooled which

  would stop a greater flow of cooling air

so much

Claims (6)

  1 annular combustion chamber for turbo engine   gas bine, characterized in that it comprises   an annular part defined by annular walls   internal (34) and external (36) walls and by an upstream end wall (38), said walls   dull and external with a plurality of openings   tures (66, 68, 70, 72) allowing the air to   entering into said annular part (32), said   upstream end wall (38) having a plurality of   a set of equidistant openings (54), a jar   conical (56) with a gaping downstream base being fixed to the   said upstream end wall (38) coaxial to each of said openings (54) of said wall (38), the included angle of each pot (56) being   in the range from 302 to 900, a fuel injector   rant (58) and a turbulence generator (60) being placed in the upstream end of each pot (56), said turbulence generator (60) being placed between the fuel injector (58) and the wall of the   pot (56), each turbulence generator (60) comprises   bearing a plurality of curved blades which can   deflect a current of air up to an angle   dre 652, at least part of the openings   said internal (34) and external (36) annular walls being oriented so as to direct an air current on the downstream face of said upstream end wall (38)   2 Annular combustion chamber according to the Claim-   cation 1, characterized in that the injector of   fuel consists of a nebulizer injector   air station (58) comprising an annulai-   re venturi (84) ending with a spray hole (86) for the injection of an air mixture   and fuel in the primary area of the combustion bre   3 Annular combustion chamber according to the Claim-   cation 1, characterized in that part of the   grooves (68) of the annular walls (34, 36) direct   gent a flow of air on said walls in direction   upstream to reinforce the air flow on the downstream face of the upstream end wall (38)   4 Annular combustion chamber according to the Claim-   cation 1, characterized in that the end wall   upstream half (38) of the combustion chamber   wears an annular heat shield made of a   reality of contiguous segments (102) fixed to said wall (38) and pierced with circular openings (104) corresponding to the diameter of the downstream part of the frustoconical pots (56) Annular combustion chamber according to Claim 4, characterized in that that each segment (102) constituting the heat shield is supplied with cooling air through an annular gap (110)   between the segment (102) and the corresponding pot (56).   6 Annular combustion chamber according to Claim-   cation 1, characterized in that it is enclosed in an annular envelope (92) traversed by a   air flow, regulating walls (94, 96) é-   both disposed between the walls of said casing (92) and of the combustion chamber to control   the speed of the air flowing between said pa-   regulating kings (94, 96) and those of the combustion chamber (34, 36)   7 Annular combustion chamber according to Claim-   cation 1, characterized in that the upstream end of said chamber is immobilized by a pin   (98) carried by each injector (58) and engages   giant in a corresponding bore formed in a part of the combustion chamber located upstream of the upstream end wall (38) 8 Gas turbine engine comprising a   annular combustion according to any of the Re-   vendications 1, 2, 3, 4, 5, 6 or 7, characterized in that the air supplying the combustion chamber, coming from the high pressure compressor of the engine,   achieves this through a diff- - discharge fuser (52)