FR2531748A1 - DOUBLE FUNCTION COOLING AIR COMBUSTION SHIRT - Google Patents

Abstract

THIS COMBUSTION CHAMBER SHIRT 58 HAS AN EXTERNAL WALL 60 AND AT LEAST ONE SEGMENT 64 OF THE INTERIOR WALL RADIALLY SPACE FROM THE OUTER WALL AND SURROUNDING THE COMBUSTION CHAMBER 54. THE OUTER WALL IS DRILLED WITH HOLES 62 FROM THE INLET WHICH ARE USED TO ENSURE THE IMPACT COOLING OF THE SEGMENTS OF THE INTERIOR WALL, THE AIR THUS INTRODUCES FORMING, BETWEEN THE TWO WALLS, AN AIR MATTRESS THAT FLOWS THROUGH OPENINGS 68 SHAPED IN THE SEGMENT (S) OF THE INTERIOR WALL TO PROVIDE DILUTION AIR TO THE COMBUSTION CHAMBER AND ALSO, THROUGH 70 HOLES TO ENSURE FLUID FILM COOLING OF THE SEGMENTS OF THE INTERIOR WALL.

Description

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  The present invention relates to combustion chamber liners for gas turbine engines and more particularly to combustion chamber liners which

  provide a dilution air stream to the compounding area

  bustion. An increase in the efficiency of gas turbine engines is obtained in part by increasing the operating temperatures inside the combustion chamber of the engine So that the engine can withstand these higher temperatures while maintaining an acceptable useful life , it is necessary not only to use extremely sophisticated materials and alloys but also to provide efficient and reliable means for cooling the shirts of

combustion chambers.

  One of the effective techniques usable for cooling

  say the combustion chamber jacket is the technique

  convection cooling by means of a fluid film.

  A boundary layer of cold air forming a protective film is directed so as to flow along an interior surface of a combustion chamber liner so as to isolate the liner from adjacent hot combustion gases. cooling air not only forms a protective barrier between the jacket and the hot gases but it also provides convection cooling of the jacket itself The air which is used in this way can be described as cooling air by film

  fluid from the combustion chamber liner.

  In addition to fluid film cooling or film cooling of the combustion chamber liner, compressed air discharged by the engine compressor is also sent into the combustion chamber liner in the interior of the combustion chamber. the purpose of supplying oxygen to the combustion process which takes place inside the combustion chamber

  significant air must be sent to the room from -

  combustion, over the entire length of the chamber structure

  of combustion, in order to maintain the combustion process.

  The air used in this way is called the air stream

dilution.

  A relatively common way used to introduce this dilution air stream has been to use dilution flow openings with relatively large radius. These openings are generally constructed as tubular members which extend through any

  the length of the combustion chamber jacket.

  One of the problems with the current use of dilution flow openings is that large amounts of compressed air are drawn into the combustion chamber through a flow path which does not fully utilize the possibilities of cooling of the air discharged by the compressor An important job was

  spent to compress this air so that it is very

  to use this air as efficiently as possible.

  Therefore, one of the purposes of the present in-

  vention is to achieve a combustion chamber liner structure which better uses the useful properties of the

dilution air stream.

  Another object of the present invention is to use

  ser air from the dilution air stream for additional purposes

  keep silent during its entry into the combustion zone.

  According to an embodiment of the present in-

  vention, compressed air taken from a region surrounding the combustion chamber is used for at least two distinct purposes First, the air is sucked through an external combustion chamber jacket so as to come to cool by impact the segments of the inner jacket of the combustion chamber Secondly, part of the air used for the impact cooling of the inner jacket flows through dilution holes to

  form the dilution flow in the combustion chamber.

  In addition, the remaining part of the air initially used for impact cooling can be sent through fluid film cooling holes to ensure the film cooling of the interior speech of the

  segments of the inner jacket of the combustion chamber.

  Compressed air can be used in these separate ways because a new jacket construction has been made.

  combustion chamber in which the jacket walls integrate

  exterior and exterior are separated by a space in which the compressed air forms an impact cooling mattress between the two jackets The air mattress serves as a source for the dilution flow and can also be a source

  fluid film cooling air.

  ^ The rest of the description refers to the figures

  attached which respectively represent Figure 1, a schematic representation, partly in section and partly exploded of a gas turbine engine in which the present invention can be used; Figure 2, a schematic sectional view of a conventional combustion chamber of a gas turbine engine Figure 3, a schematic sectional view of an embodiment of the present invention as incorporated in

  the combustion chamber of a gas turbine engine.

  In Figure 1, to which we will refer now

  nant, a conventional gas turbine engine 10 has been shown.

  in order to describe the functions of the elements inside

  laughter of this engine The engine 10 comprises an exterior cover having an inlet end 12 for receiving ambient air in an axial compressor 14 with several stages. The compressor 14 comprises grids of movable blades 16 of compressor interposed with grids of fixed blades 18 of stator The movable blades 16 of compressor are used to compress the intake air which, after being compressed, is discharged to a downstream end of the compressor 14 through a gzille 20 of compressor outlet distributor vanes, followed by an annular diffuser designated by the general reference 22 The diffuser 22 discharges the compressed air discharged by the compressor in a region 28 which surrounds a combustion chamber 30 O Parts of this compressed air discharged into the

  region 28 aui surrounds the combustion chamber 30 are

  seen in combustion chamber 30 in which they are combined with fuel and ignited to form

  high-pressure, high-speed combustion gases.

  The combustion gases are sent at high speed to a turbine part 32 The turbine part extracted from the work of the high pressure combustion gases to drive the moving blades of the compressor 14 by means of a shaft

  transmission 34 In addition, the turbine part 32 can ex-

  -tract from the additional work of the combustion gases in order to drive a shaft which provides mechanical power for any purpose; desired by the engine user For example, the shaft providing mechanical power can drive the rotating blades (not shown) of a helicopter or propeller (also not shown) or it can be used in any one of many purposes After passing through the turbine part 32, the combustion gases can be evacuated to the atmosphere through an engine nozzle 38 thus providing a thrust

directed forward to the motor 10.

  The fundamental principles of gas turbine engines, their general structure and their operation are well given to those skilled in the art. The engine shown in FIG. 1 is of the turbojet type; however, it should be understood that the present invention

  is applicable to any gas turbine engine.

  Motor 10 has been described to assist the reader in understanding the utility of the present invention in connection with

of a gas turbine engine.

  In FIG. 2 to which we will now refer

  nant, there is shown a combustion chamber 30 of the type which can be used in a gas turbine engine, such as that shown in Figure 1, for the purpose of describing the flow of air from the region 28 which surrounds the combustion chamber up to the interior of the combustion chamber itself The air contained in the region 28 which surrounds the combustion chamber 30 is strongly compressed

  the fact that it was driven by a compressor (not shown

  It is also relatively cold compared to the temperatures prevailing inside the combustion chamber in which the combustion process takes place.

  during engine operation.

  The air discharged by the compressor 30, also called the compressor discharge, is used both to maintain the combustion process and to cool the

  structure of the combustion chamber proper.

  Fuel is injected into the combustion chamber

  bustion 30 by a fuel injector 40 in the form of a fine stream of droplets which is formed; mix easily

  with compressed air to form a combustible mixture.

  The air discharged by the compressor enters the combustion chamber through various orifices formed in the structure of the combustion chamber. At its upstream end, the combustion chamber 30 comprises a dome 42 provided with air inlet orifices 44 which provide impact cooling

a dome collar 46.

  If we consider the part of the

  bust down further downstream, fluid film cooling holes 48 direct compressed air into the combustion chamber in the form of a thick film which flows along the interior walls 50 of the chamber structure

  More downstream combustion air is diluted

  produced by dilution openings 52 The purpose of this dilution air is to supply the combustion process which takes place in an interior chamber 54 The combustion gases at high pressure, and high speed, flow downstream through an outlet 56 from the chamber

  combustion in a turbine part (not shown).

  The reader will easily understand that the air discharged by the compressor introduced into the combustion chamber through the dilution openings 52 is only used for the air supply function used to maintain the

combustion process.

  In FIG. 3, to which reference will now be made, the present invention is shown as it can be used in a conventional combustion chamber 30 As in most combustion chambers, there is provided an injector 40 of fuel to an upstream end for injecting a fine atomized jet of fuel into an interior chamber 54 of the combustion chamber 30 Inside

  from chamber 54, the fine sprayed fuel jet se-

  mixes with the air and is ignited to form the high pressure and high temperature combustion gases which flow downstream from an outlet orifice 56 of the combustion chamber At its upstream end, the combustion chamber combustion takes the form of a dome 42 The dome 42 is provided with air inlet orifices 44 for the impact cooling of a dome flange 46 If we consider the part of the combustion chamber located more downstream, we

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  sees that a first row of fluid film cooling air inlet ports 49 is used to direct

  a film of cooling air along the interior walls

  of the combustion chamber in order to ensure fluid film cooling of the latter O Up

  -this point, the description of the combustion chamber 30

  shown in figure 3 is similar to that of the cham-

  conventional combustion flames of the prior art.

  Downstream of the first row of fluid film cooling orifices 49, the combustion chamber has a jacket structure 58 which is new and original and which uses dilution air in a way

  new and useful O The jacket 58 has an external wall

  liner 60 of the jacket which is, overall, constructed in a cylindrical shape around the geometrical axis of the engine so as to define the basic limits of the combustion chamber 30 A series of holes 62 of inlet cooling air are distributed around the outer wall of the jacket thus allowing the air discharged by the compressor to flow from the region 28 which surrounds the combustion chamber through the outer wall 60 of the jacket This compressed air s flowing through the air inlet holes 62 provides impact cooling of one or more segments 64 of an inner wall of

shirt.

  The segments 64 of the inner wall of the liner are radially spaced from the outer wall 60 of the liner thereby delimiting a space in which is formed an air mattress 66 of impact cooling. The mattress 66 of impact cooling serves to continuously cool the segments 64 of the inner wall of the jacket The spacing is formed structurally by peripheral annular ribs 72 which form part of the

  segments 64 of the inner wall of the shirt The nerves

  vures 72 abut against the outer wall 60 of the jacket. The air which forms the impact cooling mattress 66 can then be used in two ways

  different Part of the air mattress for cooling

  impact can be sent through holes 68

  dilution flow to constitute an im-

  bearing air used to maintain the combustion processes 54 The remaining part of the air contained in the impact-cooling mattress 66 can be sent through film-cooling holes 70

  secondary air to form a film of cooling air

  along the interior surfaces of segments 64 of

the inner wall of the shirt.

  With this new combustion chamber liner structure, compressed air can be used

  contained in region 28 which surrounds the

  bustion 30 to fulfill two or three separate and distinct functions First, compressed air is used - for impact cooling of the segments 64 of the inner wall of the jacket Second, we can use this same air used for cooling by impact, to provide a dilution flow in the chamber 54

  combustion and / or thirdly for cooling

  cementation of the segments 64 of the inner wall by fluid film

  shirt bottom Therefore, the air that forms the impact cooling mattress fills at least two

  functions and-has the possibility of fulfilling three.

  Another arrangement has been shown in a downstream part of the combustion chamber 30 in which

  impact cooling air is used only-

  for impact cooling and to form

  the dilution air flow This other embodiment

  tion of the present invention is usable in segments of combustion chambers for which fluid film cooling of the interior walls

is no longer as desirable.

  One of the extremely useful features of the present invention is that the potential cooling properties of the clear of the dilution air stream are used for impact cooling of the segments 14 of the inner wall of the jacket of the chamber. combustion 30 This function is desirable in current combustion chambers in which combustion temperatures can exceed 16490 C (30000 F) and can be very harmful to materials

  which form the combustion chamber.

  In the embodiment of the present invention

  tion shown in Figure 3, we can describe the dis-

  general contribution of the cooling air flow

  as follows From the total amount (100%) of air flowing into the interior combustion chamber

  54, approximately 30 percent flow through the injector

  fuel 40 and through the dome air inlet holes 44 formed in the dome and about another 10 percent of this air flows through the first row 49 of film cooling air inlet holes fluid The remaining 60 percent of this amount of air is used for impact cooling

  forming the impact cooling air mattress 66.

  About 2/3 of the air in the impact air mattress 66 (or about 40 percent of the total amount of air supplied to the inner chamber 54) is used for dilution flow through the holes dilution 68 and the remaining third (or about 20 percent of the total amount of air supplied to the inner chamber) is used as fluid film cooling air directed through the cooling holes 70

secondary fluid film.

  It is understood that all the percentages

  given above are only approximate percentages

  and that they can be changed to any extent

  bearing while continuing to fulfill the functions of

the present invention.

  By way of example, in an embodiment of the present invention, a combustion chamber liner can be used in which no part of the air

  impact cooling air mattress is not used

  sée for cooling by fluid film and all of this air is sent through the dilution holes as

  that air from the dilution air stream.

  Although a pre-described embodiment has been described

  fairy of the present invention as well as a variant to

  purposes of the description, it is understood that the

  technical specialists can imagine modifications

  cations and variants which do not depart from the framework of

  the invention as defined in the claims

attached.

Claims (4)

CLAIMS -1 Jacket (58) of combustion chamber (30) of gas turbine engine (10) having a compressor (14) which supplies compressed air, combustion chamber jacket characterized in that it comprises an outer wall (60) of the liner, holes (62) for supplying cooling air distributed in said outer wall of the liner allowing the compressed air to flow through the outer wall of the liner, one or more segments (64) of inner jacket wall spaced from the outer wall of the jacket to allow impact cooling from segments of the inner wall of the jacket by means of compressed air, X of the openings (68) of dilution air flow distributed in the segments of the inner wall of the jacket, this dilution flow being supplied at least in part by the air used for the impact cooling of the segments of the wall inside of the shirt.   2 Combustion chamber liner as per   vendication 1, characterized in that all of the air   dilution is provided by the air used for cooling   by impact of the segments (64) of the interior wall of the shirt.   3 Combustion chamber liner as per   vendication 1, characterized in that a mattress is formed   (66) impact cooling air between the wall ex-   inside (60) of the jacket and the segments (64) of the wall   inside of the shirt and in that the air cools   The form which forms the impact cooling mattress provides impact cooling of the segments of the inner wall of the jacket and also constitutes a   air source for the dilution stream.   4 Combustion chamber liner as per   vendication 3, characterized in that annular ribs   peripheral lairs (72) are formed in the segments (64) of the inner wall of the liner and in that the ribs abut against the outer wall (60) of the liner and thus determine, at least in part, the es - spacing between the outer wall of the shirt and the inner wall segments.   Combustion chamber liner according to claim 3, characterized in that the liner (58) comprises a dome (42) cooled by impact in an upstream part of the combustion chamber, the deme being cooled by air from impact dome cooling, and that a given amount of compressed air is sent into   the combustion chamber (30) and this quantity is distributed   generally tied so that about 30 percent of that amount is used for injecting fuel into the dome and for impact cooling air of the d Sme, about 60 percent of that amount are used to form the impact cooling mat for impact cooling of the segments (64) of the inner wall of the liner and about 10 percent of this is used only for fluid film cooling.   6 o Combustion chamber liner as per   Vendication 5, characterized in that the air used to form the impact cooling mattress (66) is distributed throughout the assembly such that approximately one third is used for the fluid film cooling of the segments (64) of the inner wall of the jacket and about two thirds are used for the dilution flow. 7 Combustion chamber liner (58) for a gas turbine engine (10) having a compressor (14), liner characterized in that it comprises: means for using the air discharged by the compressor to perform an impact cooling function of the segments (64) of the inner wall of the jacket and to use a part of this same discharge air from the compressor which serves as impact cooling air as dilution air to maintain the combustion   tion that occurs inside the combustion chamber- tion.