Recycling aircraft turbine

Abstract

Aircraft turbomachine (11) comprising: - a centrifugal compressor (12), - an annular combustion chamber (24), - an annular casing (29) extending around the chamber and delimiting an annular space (E) in which the chamber is located, and - a heat exchanger (38) comprising: a first circuit (38a) supplied with exhaust gases from the turbomachine, and a second circuit (38b) connected by volutes (40a, 40b) to an outlet (34b) of the compressor (12) and to the space (E) respectively, characterized in that the volutes (40a, 40b) are spaced apart from each other by an axial distance, and in that the second volute (40b) is connected to the space (E) by a rectifier (42) which is at least partially located outside the casing (29) and which is integrated into an annular connection duct (44) connecting the second volute (40b) to the casing (29).

Description

TECHNICAL FIELD

[0001] The present invention relates to an aircraft turbomachine equipped with a volute for implementing a recuperation cycle. BACKGROUND

[0002] An aircraft turbomachine comprises a gas generator comprising, in the gas flow direction, from upstream to downstream, at least one compressor, an annular combustion chamber and at least one turbine. The compressor is fed with air and compresses it. The compressed air is mixed with fuel and burned in the combustion chamber, which feeds the turbomachine with combustion gases. These combustion gases expand in the turbine and make the turbine rotor rotate, which in turn drives the compressor rotor through a common shaft.

[0003] The turbomachine can be equipped with one or more spools, each spool having a compressor rotor connected to the turbine rotor through a shaft.

[0004] There also exist turbomachines in which a free turbine is installed downstream of one or more spools of the turbomachine. The turbine is free if its rotor is not connected to the compressor rotor through a shaft.

[0005] It can thus be understood that a turbomachine can comprise several successive compressors (for example, a low-pressure compressor followed by a high-pressure compressor) and several successive turbines (for example, a high-pressure turbine followed by a free turbine or a low-pressure turbine).

[0006] In the present application, a conventional cycle turbomachine is defined as a turbomachine in which the compressed air leaving one or more compressors is directly fed to the combustion chamber.

[0007] Differently, a recuperation cycle turbomachine is a turbomachine in which the combustion gases flowing out of one or more turbines are used to heat the compressed air leaving one or more compressors and are intended to be fed to the combustion chamber. This technology improves the performance of the turbomachine, since the amount of fuel required to reach the operating temperature of the turbomachine is less than that required by a conventional cycle turbomachine.

[0008] Figure 1 A very schematic view of a recuperation cycle turbomachine is shown.

[0009] The turbomachine 1 comprises, from upstream to downstream, a compressor 2, an annular combustion chamber 3, a turbine 4 and a free turbine 5. The rotors of the compressor 3 and of the turbine 4 are connected together through a shaft 6 and form a single spool.

[0010] The turbomachine 1 comprises a heat exchanger 7, the first circuit of which is supplied with combustion gases from the outlet of the free turbine 5. The exchanger 7 comprises a second circuit, which is supplied with compressed air from the compressor 2 and supplies the heated compressed air to the combustion chamber 3.

[0011] When compressor 2 is centrifugal, the integration of this technology can be complex. A centrifugal compressor is a compressor that has an inlet parallel to the longitudinal axis of the turbine and an outlet radially oriented relative to that axis.

[0012] This type of compressor is associated with a system for diffuser and rectifier of compressed air flow. The system includes a diffuser-rectifier assembly, and thus includes an annular diffuser and an annular rectifier. The annular diffuser is generally radially oriented and aligned with the outlet of the centrifugal compressor, while the annular rectifier is generally axially oriented to direct the compressed air flow into the combustion chamber.

[0013] Integrated solutions for this technology have been proposed in the past, which involve using a combination of two volutes.

[0014] like Figure 2 As shown, the volute 8 is a connecting pipe spirally wound around an axis, the fluid flow cross-section of which varies. In the context of this application, the volute includes an annular connecting pipe spirally wound around the longitudinal axis A of the turbine and connected to a first port 9 and a second port 10, the first port being located at the outer periphery of the connecting pipe and oriented tangentially, and the second port being located at the inner periphery of the connecting pipe and oriented radially.

[0015] The flow cross section is maximum at the first port 9 of each volute and minimum at the circumferential end of the connecting pipe opposite the first port 10.

[0016] The second port 10 of the first volute is connected to the outlet of the diffuser, and the first port 9 of the first volute supplies the inlet of the second loop of the exchanger (solid arrow F1). The outlet of the second loop is connected to the first port 9 of the second volute, and the second port 10 of the second volute is connected to the inlet of the rectifier (dashed arrow F2).

[0017] The proposed solution first involves interlocking the volutes from their paired first ports to the smaller circumferential ends of the connecting pipes. Furthermore, the solution allows the volutes to move as close as possible to the centrifugal compressor and combustion chamber.

[0018] However, this solution has many drawbacks.

[0019] First, although it is advantageous from the point of view of plugging to bring the volutes closer to each other, or even to arrange them next to each other, it is very disadvantageous when the volutes are nested with each other, in particular from the point of view of energy and performance. Indeed, the more the volutes are nested with each other, the greater the risk of heat exchange between the flows circulating in the connecting ducts of the two volutes. The compressed air heated by the exchanger and circulating through the second volute is then cooled by the cooler compressed air intended to feed the exchanger and circulating through the first volute. This phenomenon is highlighted by the pairing of the first port, since the hottest circumferential end of the first volute is located at the coolest circumferential end of the second volute.

[0020] Furthermore, the proposed solution involves major modifications to the turbine, and is therefore relatively costly. For example, a complete redesign of the combustion chamber is necessary. The same is true of the rectifier, which must be reconfigured to precisely control the speed (in particular the Mach number) and the turn of the air flow fed to the combustion chamber.

[0021] The prior art also includes documents GB-A-2250780, US-A-2946192, EP-A2-2799666 and FR-A-1003131.

[0022] The invention provides a simple, effective and economic solution to at least some of these problems. SUMMARY

[0023] The invention relates to an aircraft turbine comprising:

[0024] - a centrifugal compressor extending around an axis A,

[0025] - an annular combustion chamber extending around the axis A,

[0026] - an annular casing extending around the axis A and the chamber, and delimiting an annular space of the chamber, and

[0027] - a heat exchanger, the exchanger comprising:

[0028] - a first circuit supplied with exhaust gases from the turbine, and

[0029] - a second circuit comprising an inlet and an outlet, the inlet of the second circuit being connected to the outlet of the compressor by a first volute, and the outlet of the second circuit being connected to the space by a second volute,

[0030] characterized in that the volutes are spaced apart from each other by an axial distance, and in that the second volute is connected to the space by a rectifier, the rectifier being at least partially located outside the casing, and in that the rectifier is integrated into an annular connecting duct connecting the second volute to the casing.

[0031] Thus, the volutes are arranged to limit the heat exchange between the fluids circulating in their connecting ducts. Moreover, the rectifier is specifically designed to optimize the supply of air to the chamber, which is very advantageous compared to the previous technique. The fact that the rectifier is located outside the casing offers multiple possibilities for the parameterization of the rectifier, including the orientation, the length, the radial dimension of the rectifier, but also the position and the dimension of the blades of the rectifier.

[0032] Advantageously, the turbomachine is a turboshaft engine, which is used for example to drive the rotating wings of a helicopter.

[0033] The turbomachine according to the application can comprise one or more of the following steps or features, which are considered independently of each other or in combination with each other:

[0034] - the volutes each have a circular or oval flow section;

[0035] - the rectifier and the second volute or even at least one part of the casing are formed in one piece; alternatively, the rectifier and the second volute or even at least one part of the casing can be formed by assembling several parts;

[0036] - the rectifier comprises blades configured so that the air flow supplied to the space has a predetermined rotation and Mach;

[0037] - the rectifier comprises two annular walls which extend coaxially and parallel to each other, the two annular walls being connected to each other by the blades, the blades each comprising an aerodynamic profile;

[0038] - the combustion chamber is of the inverted type and comprises a chamber bottom at the downstream end of the combustion chamber, the second volute being located downstream of a plane perpendicular to the axis and passing through the chamber bottom;

[0039] - the rectifier is inclined with respect to a plane perpendicular to the axis at an angle a comprised between 0° and 90°, the angle being measured in a plane passing through the axis;

[0040] - the internal diameter of the second volute is greater than or equal to the external diameter of the casing;

[0041] - the internal diameter of the first volute is less than the external diameter of the casing;

[0042] - the first and second volutes comprise bosses with threaded holes, and / or attachment flanges, the attachment flanges being formed in one piece with the rest of the volutes; alternatively, the first and second volutes can be formed by assembling several parts; for example, the parts can be formed by additive manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0043] Further features and advantages of the present invention will become apparent from the detailed description that follows, with reference to the accompanying drawings, in which:

[0044] [ Figure 1 ] Figure 1 is a very schematic view of a recuperated aircraft turbine;

[0045] [ Figure 2 ] Figure 2 is a very schematic view of a volute;

[0046] [ Figure 3 ] Figure 3 is a partial schematic view of an axial section of a recuperated aircraft turbine according to a first embodiment of the invention; and

[0047] [ Figure 4 ] Figure 4 is a view similar to Figure 3 , showing a second embodiment of the invention. DETAILED DESCRIPTION

[0048] Figure 1 and Figure 2 have been described above.

[0049] Figure 3 and Figure 4 show a preferred embodiment of an aircraft turbine 11.

[0050] The turbine 11 is partially shown in Figure 3 and Figure 4 and generally comprises at least one compressor, an annular combustion chamber and at least one turbine.

[0051] In the example shown, the turbine 11 comprises a centrifugal compressor 12, which is partially shown.

[0052] The compressor 12 has an annular shape around an axis A, which is a longitudinal axis of the turbine 11. The compressor 12 comprises a stator 16 and a bladed rotor 18, called impeller, which rotates within the stator 16 around the axis A.

[0053] The compressor 12 has an inlet (not shown) axially upstream and an outlet 22 radially outward from the axis A. Here, the terms upstream and downstream refer to the general flow of air and gases in the turbine 11.

[0054] The turbine 11 also comprises a combustion chamber 24 downstream of the compressor 12.

[0055] The combustion chamber 24 comprises two annular walls, respectively an inner annular wall 24a and an outer annular wall 24b, which define between them an annular cavity into which compressed air from the compressor 12 and fuel from the injector 26 are injected and mixed.

[0056] The walls 24a, 24b are connected to each other by a chamber bottom 28, which has an annular shape and comprises an orifice (not visible) for passing the compressed air from the compressor 12 to feed the chamber 24.

[0057] The combustion chamber 24 is surrounded by an outer annular casing 29, which in particular carries the injector 26. This casing 29 defines an annular space E which houses the chamber 24.

[0058] In the example shown, the chamber 24 is of the inverted type, since its chamber bottom 28 is located on the downstream side of the chamber. The outlet of the chamber 24 is located on the upstream side of the chamber and is connected to one or more turbines 30 located downstream of the chamber.

[0059] The combustion gases injected into the turbine 30 expand and drive the rotor of the turbine, which is connected by a shaft to the rotor 18 of the compressor 12 to rotate around the axis A.

[0060] The combustion gases are then discharged into a combustion gas discharge nozzle, not shown.

[0061] As Figure 3 shown, in a conventional cycle turbine comprising many elements identical or similar to the recuperated cycle aircraft turbine 11, the connection from the outlet of the compressor 12 to the combustion chamber 24 is made through an air diffusion and fairing system, also called a diffuser-fairing.

[0062] This diffuser-fairing comprises:

[0063] - an annular diffuser 34, which is oriented substantially radially and comprises at its inner periphery an inlet 34a fed by the compressor 12 and radially aligned with the outlet 22 of the compressor, and at its outer periphery an outlet 34b which opens radially outwardly; and

[0064] - an annular fairing 36 (shown in dotted lines in Figure 3 to illustrate that this arrangement only exists in a conventional cycle turbine), which is oriented substantially axially and comprises at its upstream end an inlet 36a and at its downstream end an outlet 36b for supplying the space E and the combustion chamber 24.

[0065] A diffuser 34 is located upstream of the chamber 24 and of its walls 24a, 24b, and a rectifier 36 extends around the chamber 24 and its walls 24a, 24b and within the casing 29. The diffuser 34 is attached by clamping to the stator 16 of the compressor 12. The rectifier 36 can be clamped to the casing 29.

[0066] The diffuser 34 and the rectifier 36 are generally vane-shaped.

[0067] In a conventional cycle turbine, the outlet 34b of the diffuser 34 is connected directly to the inlet 36a of the rectifier 36, for example by a connecting duct 37 bent into an L shape, which connects the outlet 34b of the diffuser 34 to the inlet 36a of the rectifier 36. Figure 3 This connection is shown in dotted lines in Figure 1 to illustrate that this arrangement exists only in a conventional cycle turbine. In other words, the compressed air leaving the compressor 12 is directly fed to the combustion chamber 24.

[0068] According to the invention, the turbine 11 is of recuperation cycle type, which means that the compressed air leaving the compressor 12 is heated before being injected into the combustion chamber 24.

[0069] The compressed air is heated on the one hand by a heat exchanger 38 and on the other hand by a set of two volutes 40a, 40b.

[0070] The heat exchanger 38 is shown schematically and essentially comprises two circuits 38a, 38b, namely:

[0071] - a first circuit 38a, the inlet 38aa of the first circuit being connected to means for sampling exhaust gases from the outlet of the turbine 30 or from the aforementioned exhaust nozzle, and the outlet 38ab of the first circuit also being connectable to the exhaust nozzle to release these gases into the atmosphere, and

[0072] - a second circuit 38b, the second circuit having an inlet 38ba and an outlet 38bb connected to the volute assembly 40a, 40b.

[0073] The volutes 40a, 40b are aligned on the axis A but are separated, so as to be spaced apart from each other by an axial distance.

[0074] Each volute 40a, 40b comprises connecting ducts spirally wound around the axis A, as discussed above in relation to the diffuser 34. Figure 2

[0075] Preferably, the volutes 40a, 40b each have a circular or oval flow cross-section along their entire circumferential extent. The term "oval" means any elliptical, ovoid or oblong shape. However, other shapes are also possible. The flow cross-section of the connecting ducts varies, preferably gradually, around its circumference.

[0076] ​Each volute 40a, 40b comprises a first port 9 located at the outer periphery of the connecting duct and oriented in a tangential direction, and a second port 10 located at the inner periphery of the connecting duct and oriented in a substantially radial direction. In Figure 3 only the second port 10 is visible.

[0077] The second port 10 of the volute 40a is connected to the outlet 34b of the diffuser 34, the first port 9 of the volute feeding the inlet 38ba of the second circuit 38b of the exchanger 38. The outlet 38bb of this second circuit 38b is connected to the first port 9 of the second volute 40b, the second port 10 of the second volute being connected to the annular space E in which the chamber 24 is located, through a new rectifier 42.

[0078] The ports 9 can each be substantially tubular and are respectively coupled to the inlet 38ba and to the outlet 38bb of the exchanger 38, through suitable means.

[0079] In the example shown, the volute 40a is located upstream of the volute 40b. The distance between the volutes 40a, 40b eliminates any risk of heat exchange between the air flows circulating simultaneously in the two volutes.

[0080] Furthermore, the volutes 40a, 40b extend around and away from the casing 29 and are clamped to the casing 29, as will be described in detail below.

[0081] The connecting duct of each volute 40a, 40b comprises an annular outer layer defining the aforementioned flow section, and which has a substantially constant thickness over its circumferential extent around the axis A and over its entire axial extent, for example as Figure 3 shown.

[0082] The volute 40a is substantially aligned with the outlet of the diffuser 34 and of the compressor 12. The internal diameter Dl of the volute 40a is less than the external diameter Dext of the casing 29.

[0083] The volute 40a comprises a plurality of bosses 46 protruding from the outer layer of the volute, arranged in an annular manner, the bosses comprising blind threaded holes 48 for screwing in screws 50.

[0084] These bosses 46 abut against annular flanges 52 of the casing 29 of the turbomachine or of another external casing, these flanges 52 comprising orifices for the passage of the screws 50.

[0085] The second port 44 of the volute 40a comprises two annular walls 60, 62 extending around the axis A and defining an air passage between them.

[0086] Walls 60 and 62 are generally parallel and project radially inward from the inner periphery of the volute 40a. In the example shown, walls 60 and 62 are radial and extend radially inward.

[0087] In the example shown, the volute 40a is integrally formed with these walls 60, 62.

[0088] The walls 60, 62 of the volute 40a have free ends opposite the connecting pipe, which define a generally radially oriented connector 64 for connection to the outlet 34b of the diffuser 34. The connector 64 is annular and can be secured to the turbine housing 29 or another housing by screws or the like.

[0089] In the example shown, walls 60 and 62 have a thickness similar to or the same as the outer layer of the volute 40a.

[0090] According to the invention, the second port 10 of the rectifier 42 and the volute 40b is integrated into an annular connecting pipe 44, which connects the volute 40b to the housing 29 of the chamber and extends at least partially protruding outside the housing. The volute 40b is located downstream of the chamber 24.

[0091] The connecting conduit 44 includes two annular walls 70, 72 that extend about axis A and define an air passage between them. The walls 70, 72 are generally parallel and project from the housing with at least one axial component.

[0092] exist Figure 3 In the illustrated embodiment, the connecting pipe 44 extends generally axially. Figure 4 In the illustrated embodiment, the connecting pipe 44 is inclined relative to a plane P1 perpendicular to axis A at an angle α between 0° and 90°, which is measured in a plane passing through the axis. Angle α is preferably strictly greater than 0° and preferably strictly less than 90°.

[0093] In the example shown, walls 70 and 72 have a thickness similar to or the same as the outer layer of the volute 40b.

[0094] The volute 40b is integral with a portion of the housing 29, which includes an annular flange 74 for attachment to other flanges 76 of the turbine.

[0095] In the example shown, the volute 40b is connected to the upstream flange 74a, which is used to attach to the flange 52 and the boss 46, which is used to attach the volute 40a. The aforementioned screw 50 passes through the holes in the flanges 45 and 74a and is screwed into the blind hole 48 in the boss 46.

[0096] The volute 40b is also connected to a downstream flange 74b for attachment to a flange 76 of an inner casing of the chamber 24, for example.

[0097] In the case where the inner diameter D2 of the volute 40b is greater than the outer diameter Dext of the casing 29. Figure 4

[0098] The rectifier 42 comprises vanes 78 extending between the walls 70, 72 and configured so that the air flow supplied to the space E has a predetermined swirl and Mach. In practice, the vanes 78 have an aerodynamic profile and are sized according to the flow rate and speed of the air leaving the exchanger 38 so that the air leaving the rectifier 42 has a Mach (or speed) and a swirl (speed profile around the axis A) that is particularly suitable for the chamber 24, in particular for the type, shape and size of the chamber 24. This limits the pressure drop in the space E and optimizes the air supply to the chamber 24, thus optimizing the performance of the turbomachine. The vanes 78 can have a longitudinal dimension along the elongated axis of the connection duct 44 that is at least 80% of the length of the connection duct.​

Claims

1. An aircraft turbine (11), the aircraft turbine comprising: -A centrifugal compressor (12) extending around axis A, - An annular combustion chamber (24) extending around said axis A, - An annular housing (29), the annular housing extending about the axis A and the chamber, and defining the annular space (E) containing the chamber, and - Heat exchanger (38), the heat exchanger comprising: - First circuit (38a), the first circuit is supplied with exhaust gas from the turbine, and - A second loop (38b), comprising an inlet (38ba) and an outlet (38bb), wherein the inlet of the second loop is connected to the outlet (34b) of the compressor (12) via a first volute (40a), and the outlet of the second loop is connected to the space (E) via a second volute (40b). The volutes (40a, 40b) are spaced apart from each other by an axial distance, and the second volute (40b) is connected to the space (E) via a rectifier (42) located at least partially outside the housing (29), and the rectifier is integrated into an annular connecting pipe (44) that connects the second volute (40b) to the housing (29).

2. The turbine (11) according to claim 1, wherein, Each of the volutes (40a, 40b) has a circular or oval flow cross section.

3. The turbine (11) according to claim 1 or 2, wherein, The rectifier (42) and the second volute (40b) or even at least a portion of the housing (29) are formed as one unit.

4. The turbine (11) according to any one of the preceding claims, wherein, The rectifier (42) includes blades (78) configured such that the airflow supplying the space (E) has a predetermined rotation and Mach.

5. The turbine (11) according to the preceding claim, wherein, The rectifier (42) includes two annular walls (70, 72) that are coaxial and extend parallel to each other and are connected to each other by the blades (78), each blade having an aerodynamic profile.

6. The turbine (11) according to any one of the preceding claims, wherein, The combustion chamber (24) is inverted and includes a chamber bottom (28) at its downstream end, with the second volute (40b) located downstream of a plane (P1) perpendicular to the axis (A) and passing through the chamber bottom.

7. The turbine (11) according to any one of the preceding claims, wherein, The rectifier (42) is tilted at an angle α between 0° and 90° relative to a plane (P1) perpendicular to the axis (A), the angle being measured in a plane passing through the axis.

8. The turbine (11) according to any one of the preceding claims, wherein, The inner diameter (D2) of the second volute (40b) is greater than or equal to the outer diameter (Dext) of the shell (29).

9. The turbine (11) according to any one of the preceding claims, wherein, The inner diameter (D1) of the first volute (40a) is smaller than the outer diameter (Dext) of the shell (29).

10. The turbine (11) according to any one of the preceding claims, wherein, The first and second volutes (40a, 40b) include a boss (46) with a threaded hole (48) and / or an attachment flange (74) integrally formed with the rest of these volutes.

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