Injection system for a turbomachine combustion chamber with optimized sealing between an injector and a sliding bushing

Abstract

The invention relates to an injection system (42) for injecting a mixture of air and fuel into a turbomachine combustion chamber (18), said injection system comprising a sleeve (52) externally delimiting a passage (64) in which a fuel injector nozzle (54) is mounted so as to establish with the sleeve (52) a ball joint sliding along an injection axis (44) of the injection system. The fuel injector nozzle (54) comprises an annular injector spur (72) projecting from an outer surface (68) of the fuel injector nozzle (54) so as to delimit, around said outer surface, an annular groove (74). The sleeve (52) has an annular sleeve spur (76) engaged with clearance in said annular groove (74) so as to define, with the latter, a sealing baffle (78) at an inlet of said passage (64).

Description

[0001] Description

[0002] Title: Injection system for turbomachine combustion chamber with optimized sealing between injector and sliding feedthrough

[0003] Technical field

[0004] The present invention relates to the field of injection systems intended for the injection of air and fuel mixtures into the combustion chambers of turbomachines, in particular turbojets intended for the propulsion of aircraft.

[0005] State of the prior art

[0006] A turbomachine, such as a turbojet, comprises one or more compressor(s) delivering pressurized air to a combustion chamber where the air mixed with fuel is ignited to generate hot combustion gases. These gases flow downstream of the chamber to one or more turbine(s) which transform(s) the energy thus received to drive the compressor(s) in rotation and provide the work necessary, for example, to propel an aircraft. Typically, an annular combustion chamber comprises an inner annular wall and an outer annular wall, connected together at their upstream end by an annular chamber end wall. The chamber end wall has, circumferentially spaced apart, a plurality of passages each receiving an injection system in the middle of which is positioned a fuel injector nozzle, the assembly allowing the supply of a mixture of air and fuel into the combustion chamber.

[0007] Such an injection system comprises in particular a sleeve, also called a "sliding feedthrough", externally delimiting a passage in which the corresponding fuel injector nozzle is mounted so as to establish with the sleeve a sliding ball joint connection along an injection axis, generally corresponding to an axis of the sleeve. For this purpose, the fuel injector nozzle generally has an external surface comprising an annular portion with a convex axial section. Such a connection method is generally desirable to allow easy and rapid assembly and disassembly of the injector nozzle during maintenance operations. The freedom of movement offered by such a connection method also makes it possible to compensate for differential movements, in particular of thermal origin, between the combustion chamber and the injector nozzle.

[0008] Despite efforts to enable a precise fit of the fuel injector nozzle in the socket to prevent unwanted air from entering the injection system, these parts tend to wear during operation, which can result in uncontrolled air leakage around the injector nozzle, which may be likely to modify the distribution of the air flow in the injection system and in the combustion chamber and in particular to disturb the swirl flow within the injection system.

[0009] Statement of the invention

[0010] The invention aims to remedy this problem at least in part.

[0011] To this end, it proposes an injection system for injecting a mixture of air and fuel into a turbomachine combustion chamber, comprising a sleeve externally delimiting a passage in which a fuel injector nose is mounted so as to establish with the sleeve a sliding ball joint connection along an injection axis of the injection system.

[0012] According to the invention, the fuel injector nose comprises an annular injector nozzle extending projecting from an external surface of the fuel injector nozzle so as to delimit, around said external surface, an annular groove, and the sleeve has an annular sleeve nozzle engaged with clearance in said annular groove so as to define, with the latter, a sealing baffle at an inlet of said passage.

[0013] The sealing baffle generally makes it possible to limit air leaks around the injector nozzle within the passage delimited by the sleeve, by inducing a pressure drop at the inlet of said passage. In embodiments, said sealing baffle is a first sealing baffle, and the injection system comprises a skirt extending projecting from the sleeve so as to delimit around the sleeve an annular groove in which the annular injector nozzle is engaged with clearance so as to define a second sealing baffle fluidically in series with said first sealing baffle.

[0014] In embodiments, the injection system comprises a bowl, and at least one air intake swirler external to the injector nose and opening upstream of the bowl to inject air into the injection system having a rotating movement around the injection axis of the injection system.

[0015] In embodiments, the injector nozzle is of the aeromechanical type. In particular, the air intake swirler is advantageously of the radial type.

[0016] In other embodiments, the injector nose is of the aerodynamic type.

[0017] In such embodiments, the air intake swirler may have an axial inlet, and an axial-radial outlet, an upstream portion of which is delimited internally by a downstream portion of an external surface of the sleeve, of frustoconical shape converging downstream, and a downstream portion of which is delimited internally by a downstream end portion of the external surface of the injector nose extending substantially in aerodynamic continuity with the downstream portion of the external surface of the sleeve when the injector nose is in a nominal axial position.

[0018] In such embodiments, the injector nose may include an internal air intake swirler surrounded by an annular fuel ejection passage.

[0019] In embodiments, the annular groove is open in a direction from an inlet of the passageway to an outlet of the passageway.

[0020] In embodiments, the annular bushing nose is formed by an upstream free end of the bushing. In embodiments, the annular injector nose takes the form of a flange extending radially outwardly from the outer surface of the fuel injector nose and terminating in an annular rim extending in the direction from the passage inlet to the passage outlet, to a free end of the annular injector nose.

[0021] The invention also relates to a turbomachine for an aircraft, comprising a combustion chamber and at least one injection system of the type defined above for supplying the combustion chamber with a mixture of air and fuel.

[0022] Brief description of the drawings

[0023] The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0024] [Fig. 1] is a schematic axial sectional view of a turbomachine intended for aircraft propulsion;

[0025] [Fig. 2] is a schematic half-view in axial section of a combustion chamber within the turbomachine of Figure 1;

[0026] [Fig. 3] is a schematic axial sectional view of an injection system of a known type, suitable for equipping the combustion chamber of Figure 2;

[0027] [Fig. 4] is a view similar to Figure 3, illustrating an injection system according to an embodiment of the invention, also suitable for equipping the combustion chamber of Figure 2;

[0028] [Fig. 5] is a view similar to Figure 3, illustrating an injection system according to another embodiment of the invention, also suitable for equipping the combustion chamber of Figure 2.

[0029] Throughout these figures, like references may designate like or similar elements. Detailed description of preferred embodiments

[0030] Figure 1 illustrates a turbomachine 10, for example a twin-spool, dual-flow turbojet engine for aircraft, generally comprising a fan 12 intended for the suction of an air flow Fl dividing downstream of the fan into a primary flow F2 circulating in a primary flow channel, hereinafter referred to as the primary vein PV, and a secondary flow F3 circulating in a secondary flow channel, hereinafter referred to as the secondary vein SV, arranged around the primary vein PV.

[0031] By way of illustration, the turbomachine generally comprises a low-pressure compressor 14, a high-pressure compressor 16, a combustion chamber 18, a high-pressure turbine 20 and a low-pressure turbine 22 which jointly define the primary stream PV. The respective rotors of the high-pressure compressor and the high-pressure turbine are connected by a shaft called the “high-pressure shaft”, while the respective rotors of the low-pressure compressor and the low-pressure turbine are connected by a shaft called the “low-pressure shaft”, in a well-known manner. These rotors are rotatably mounted around an axis 28 of the turbomachine.

[0032] Throughout this description, the axial direction X is the direction of the axis 28. We further consider a first cylindrical coordinate system centered on the axis 28, in which a radial direction R is at all points orthogonal to the axis 28 and passes through the latter, while an orthoradial or circumferential direction C is at all points orthogonal to the radial direction R and to the axis 28. A transverse plane is a plane orthogonal to the axis 28. The terms “internal” and “external” refer respectively to a relative proximity, and a relative distance, of an element with respect to the axis 28. Finally, the “upstream” and “downstream” directions are defined with reference to the general direction FD of the flow of gases in the primary PV and secondary SV veins of the turbomachine, in the axial direction X.

[0033] Figure 2 illustrates the combustion chamber 18 and its immediate environment, in a known configuration. Conventionally, this combustion chamber, which is of the annular type, comprises two coaxial annular walls, respectively radially internal 32 and radially external 34, which extend from upstream to downstream, in the aforementioned direction FD, around the axis of the combustion chamber which merges with the longitudinal axis 28 of the turbomachine. These radially internal 32 and radially external 34 annular walls are connected to each other at their upstream end by an annular chamber bottom wall 40, so that these walls externally delimit an interior volume V of the combustion chamber 18.

[0034] The annular chamber bottom wall 40 comprises passages distributed around the longitudinal axis 28 and through which are respectively mounted injection systems 42 configured to each deliver a layer of a mixture of air and fuel centered along a respective injection axis 44.

[0035] In addition, the combustion chamber is generally equipped with one or more spark plugs 45 mounted through the outer annular wall 34.

[0036] In operation, a portion 46 of an air flow 48 coming from a compressor such as the high-pressure compressor 16 supplies the injection systems 42 while another portion 50 of this air flow bypasses the combustion chamber by flowing downstream along the coaxial walls 32 and 34 of this chamber and allows, in certain cases, the supply of air inlet orifices provided within these walls 32 and 34.

[0037] As shown in Figure 3, each injection system 42 generally comprises, from upstream to downstream, a sleeve 52, sometimes called a “sliding feedthrough”, intended to receive a fuel injector nozzle 54, as well as one or more air intake swirlers 56, 58 (sometimes called “swirlers”), possibly separated from each other by a wall 59 with a radially internal end of convergent-divergent shape, commonly called a “venturi”, for injecting air into the injection system having a gyratory movement in a circumferential swirl direction SCI around the injection axis 44, and finally a bowl 60, sometimes called a “mixing bowl”, which essentially takes the form of a wall of revolution having a shape which diverges downstream. These elements are centered relative to the injection axis 44.

[0038] The present description refers to a second cylindrical coordinate system centered on the injection axis 44 of an injection system considered, and in which an axial direction X' is parallel to the injection axis 44, a radial direction R' is at all points orthogonal to the injection axis 44 and passes through the latter, while an orthoradial or circumferential direction C' is at all points orthogonal to the radial direction R' and to the injection axis 44.

[0039] Each of the swirlers comprises, in a well-known manner, fins 56A, 58A which delimit between them air channels with respective axes oriented in directions each having a radial component and a circumferential component so as to give a swirling character to the air flow passing through the swirler.

[0040] The injection system illustrated in Figure 3 comprises two successive swirlers 56 and 58, both of the radial type, i.e. oriented transversely to the injection axis 44. In other words, the respective axes of the air channels defined between the fins of such swirlers are included in a plane transverse to the injection axis 44, i.e. extend in respective directions having no axial component. The present disclosure is however also applicable to injection systems comprising one or more swirlers of the axia l-radia I type, i.e. in which the respective axes of the air channels extend in respective directions having an axial component and a radial component, or even to injection systems comprising one or more swirlers of the axial type, i.e. in which the respective axes of the air channels extend in respective directions having no radial component.Injection systems comprising a combination of spirals of several of the above-mentioned types are also possible, as are injection systems comprising only a single spiral, as will become more apparent in the following.

[0041] Generally speaking, two types of injectors are commonly used for turbomachine combustion chambers: aerodynamic injectors and aeromechanical injectors. Aerodynamic injectors inject fuel at a pressure close to that of the air injected by the injection system. A single fuel supply circuit is generally sufficient to cover the entire fuel flow range that such an injector must cover. In aeromechanical injectors, the fuel is injected at a pressure much higher than that prevailing in the combustion chamber. This contributes to good fuel atomization quality, even when the pressure and air flow in the chamber are low. To cover the entire fuel flow range while maintaining an acceptable fuel pressure, however, two fuel supply circuits are generally necessary.Additionally, the higher fuel pressure requirement generally results in heavier fuel delivery systems. Aeromechanical injectors are particularly popular for improving fuel atomization and low-flow combustion.

[0042] The injector nose 54 of the injection system of Figure 3 is of the aeromechanical type. The internal configuration of the latter will not be detailed in the present description and is foreign to the object of the present invention.

[0043] In a manner known per se, the sleeve 52 comprises an annular wall 62 externally delimiting a passage 64 of generally tubular shape, in which the fuel injector nose 54 is mounted so as to establish a sliding ball joint connection with the sleeve (at the area 66 in FIG. 3). For this purpose, the fuel injector nose 54 has an external surface 68 comprising an annular portion 70 with a convex axial section.

[0044] Such a connection method is generally desirable to allow easy and rapid assembly and disassembly of the injector nose 54 during maintenance operations. The freedom of movement offered by such a connection method also makes it possible to compensate for differential movements, in particular of thermal and vibratory origin, between the walls delimiting the combustion chamber 18 and the injector nose 54.

[0045] Despite the efforts made to allow a precise adjustment of the fuel injector nozzle 54 in the sleeve 52 to avoid parasitic air inlets into the injection system, these parts tend to wear during operation, which can result in an uncontrolled leak of air around the injector nozzle 54 within the passage 64, which may be likely to modify the distribution of the air flow in the injection system and in the combustion chamber and to disturb in particular the swirling flow within the injection system. Document WO2017 / 072451 illustrates in its figure 3 a possible solution to this problem in the context of an injection system with an aerodynamic injector nozzle incorporating a central axial swirler surrounded by an annular liquid fuel ejection channel, and in which the sleeve receiving the injector nozzle internally delimits a swirler with axial inlet and axial-radial outlet.This solution consists of providing, downstream and at a distance from the sliding ball joint connection zone, a flow restriction zone, defined by a relatively small clearance (not visible in Figure 3 of document WO2017 / 072451) between a downstream end of a portion of the sleeve of convergent shape towards the downstream and a downstream end of the injector nose, said flow restriction zone being separated from the sliding ball joint connection zone by a zone with greater clearance between the injector nose and the sleeve. The flow restriction zone makes it possible to limit the flow of any leaks around the injector nose at the sliding ball joint connection zone, in the event of wear of the latter.

[0046] However, the possibilities of reducing the clearance at the flow restriction zone are limited by the need to allow movement of the injector nose in rotation within the sleeve at the sliding ball joint connection zone, in particular around axes oriented transversely to the injection axis, and this is all the more so since the distance between the sliding ball joint connection zone and the flow restriction zone, imposed by dimensioning parameters of the injection system, tends to amplify the relative proximity between the injector nose and the sleeve for a given angular displacement of the injector nose.

[0047] In addition, the flow restriction zone induces the presence of an aerodynamic step between the downstream end of the sleeve and the downstream end of the injector nozzle, in particular when the injector nozzle is offset downstream or upstream relative to its nominal position within the passage defined by the sleeve. Due to such a location, such an aerodynamic step is likely to negatively disrupt the interaction between the swirling air and fuel flow from the injector nozzle and the swirling air flow from the swirler.

[0048] The invention aims as much as possible to resolve these problems and avoid these drawbacks of known injection systems, whether they are injection systems of the type described above with reference to Figure 3 or injection systems of the type described in the aforementioned document WO2017 / 072451.

[0049] Figure 4 thus illustrates an injection system 42 similar to that of Figure 3 but which is distinguished from the latter by the fact that the fuel injector nose 54 comprises an annular injector beak 72 extending projecting from the external surface 68 of the injector nose 54 so as to delimit, around this external surface 68, an annular groove 74 open in the direction going from an inlet of the passage 64 towards an outlet of this passage 64, that is to say in the downstream direction. In addition, the sleeve 52 has an annular sleeve beak 76 engaged with clearance in the annular groove 74, so as to define, with the latter, a sealing baffle 78 at the inlet of the passage 64.By sealing baffle, it is necessary to understand a meander with restricted section, here forcing the air which would penetrate into the passage 64 around the injector nose 54 to circulate firstly upstream to bypass the upstream end of the sleeve 52 before returning downstream in the passage 64. In the context of the present invention, such a baffle is of generally annular geometry, taking into account the annular geometry of the elements which define it.

[0050] In the illustrated example, the annular injector nozzle 72 takes the form of a collar 72A extending radially outwardly from the outer surface 68 and terminating in an annular rim 72B, for example of generally cylindrical shape, extending downstream to a free end. In addition, in the illustrated example, the annular sleeve nozzle 76 is formed by the upstream free end of the sleeve 52.

[0051] The sealing baffle 78 generally makes it possible to limit air leaks around the injector nozzle 54 within the sleeve 52 by inducing a pressure drop at the inlet of the passage 64.

[0052] In the illustrated embodiment, the injection system further comprises a cylindrical skirt 80 extending radially outward from the sleeve 52 and extending upstream to a free end, so as to delimit around the sleeve 52 an annular groove 82 open upstream and in which the annular injector nozzle 72 is engaged with play. The injector nose 54 and the sleeve 52 thus jointly define a second sealing baffle 84, that is to say a second meander with restricted section, in series with the aforementioned sealing baffle 78, called the first sealing baffle in this case.Such a second sealing baffle 84 makes it possible to force the air which would enter the passage 64 around the injector nose 54 to flow firstly downstream to bypass the free end of the annular injector nozzle 72, before flowing upstream to bypass the upstream end of the sleeve 52 and then returning downstream in the passage 64.

[0053] In the illustrated example, the cylindrical skirt 78 extends upstream beyond the annular injector nozzle 72 so as to define an annular inlet passage 86 for the second sealing baffle 82.

[0054] Figure 5 illustrates an injection system of the type described in document WO2017 / 072451, but which is distinguished from the latter by the presence of a baffle similar to that described above, at the inlet of the passage 64 receiving the injector nose 54.

[0055] Thus, the sleeve 52 has an internal surface 52A which externally delimits the passage 64, and an external surface 52B-52C which internally delimits an air intake swirler 56 external to the injector nose 54, of the type having an axial inlet 56A and an axial-radial outlet 56B-56C. For this purpose, the external surface comprises an upstream portion 52B of generally cylindrical shape which delimits the inlet 56A of the swirler, and a downstream portion 52C of generally frustoconical shape converging downstream which delimits an upstream portion 56B of the outlet of the swirler.

[0056] The air intake spiral 56 is delimited externally by an annular wall 88 which extends downstream so as to form the bowl 60.

[0057] The injector nose 54, of aerodynamic type, comprises an internal air intake swirler 90 of axial type, arranged in the center of the injector nose, and around which is defined an annular passage 92 for ejecting liquid fuel, itself surrounded by an external wall of the injector nose which defines the external surface 68 thereof. This external surface 68 comprises an annular portion 70 with a convex axial section to establish the sliding ball joint connection with the sleeve 52, and a downstream end portion 94 which extends the annular portion 70 downstream and which is advantageously of frustoconical shape converging downstream. In this embodiment, the downstream end portion 94 internally delimits a downstream portion 56C of the outlet of the swirler 56.In particular, the downstream end portion 94 extends substantially in aerodynamic continuity with the downstream portion 52C of the external surface of the sleeve 52 when the injector nose 54 is in a nominal axial position (corresponding to the position visible in FIG. 5).

[0058] As in the embodiment of Figure 4, the upstream end of the sleeve 52 forms an annular sleeve beak 76, while the injector nose 54 comprises an annular injector beak 72 extending projecting from the external surface 68 of the injector nose 54 so as to delimit, around this external surface 68, an annular groove 74 open in the direction going from an inlet of the passage 64 towards an outlet of this passage 64, that is to say in the downstream direction.

[0059] As in the embodiment of Figure 4, the annular socket beak 76 is engaged with play in the annular groove 74, so as to define, with the latter, a sealing baffle 78 at the entrance to the passage 64.

[0060] The sealing baffle 78 here again makes it possible to limit air leaks around the injector nose 54 within the sleeve 52 by inducing a pressure drop at the inlet of the passage 64.

[0061] The configuration of the injection system further allows a relative axial proximity between the sealing baffle 78 and the sliding ball joint connection zone 66, because the distance between these elements does not depend on the total axial extent of the injector nose 54 and is in particular indifferent to the axial extent of the downstream end portion 94 of the external surface 68 of the injector nose. Such relative axial proximity results in a lesser amplification of the relative displacements between the injector nose 54 and the sleeve 52, at the sealing baffle 78, for a given angular displacement of the injector nose 54 at the sliding ball joint connection zone 66, compared with the injection systems of the type described in document WO2017 / 072451.

[0062] In addition, the aerodynamic step, which would result from an offset of the injector nose 54 downstream or upstream relative to its nominal position, would be located upstream of the downstream end portion 94 of the external surface 68 of the injector nose, and therefore at a distance upstream of the interaction zone between the swirling air and fuel flow coming from the injector nose 54 and the swirling air flow coming from the swirler 56, so that the impact of such an aerodynamic step on this interaction zone would be considerably more limited than in the case of the injection system of document WO2017 / 072451.

Claims

Claims 1. Injection system (42) for injecting a mixture of air and fuel into a combustion chamber (18) of a turbomachine, comprising a sleeve (52) externally delimiting a passage (64) in which a fuel injector nose (54) is mounted so as to establish with the sleeve (52) a sliding ball joint connection along an injection axis (44) of the injection system, characterized in that the fuel injector nose (54) comprises an annular injector nozzle (72) extending projecting from an external surface (68) of the fuel injector nozzle (54) so as to delimit, around said external surface, an annular groove (74), and in that the sleeve (52) has an annular sleeve nozzle (76) engaged with clearance in said annular groove (74) so as to define, with the latter, a sealing baffle (78) at an inlet of said passage (64).

2. Injection system according to claim 1, wherein said sealing baffle is a first sealing baffle (78), said injection system comprising a skirt (80) extending projecting from the sleeve (52) so as to delimit around the sleeve (52) an annular groove (82) in which the annular injector nozzle (72) is engaged with play so as to define a second sealing baffle (84) fluidically in series with said first sealing baffle (78).

3. Injection system according to claim 1 or 2, comprising a bowl (60), and at least one air intake spiral (56) external to the injector nose (54) and opening upstream of the bowl (60) to inject air into the injection system having a rotating movement around the injection axis (44) of the injection system.

4. Injection system according to claim 3, in which the injector nose (54) is of the aeromechanical type.

5. Injection system according to claim 4, wherein the air intake swirler (56) is of the radial type.

6. Injection system according to claim 3, wherein the injector nose (54) is of the aerodynamic type.

7. Injection system according to claim 6, in which the air intake swirler (56) has an axial inlet (56A), and an axial-radial outlet of which an upstream portion (56B) is delimited internally by a downstream portion (52C) of an external surface of the sleeve (52), of shape converging downstream, and of which a downstream portion (56C) is delimited internally by a downstream end portion (94) of the external surface (68) of the injector nose (54) extending substantially in aerodynamic continuity with the downstream portion (52C) of the external surface of the sleeve (52) when the injector nose (54) is in a nominal axial position.

8. An injection system according to claim 6 or 7, wherein the injector nose (54) comprises an internal air intake swirler (90) surrounded by an annular fuel ejection passage (92).

9. Injection system according to any one of claims 1 to 8, wherein the annular groove (74) is open in a direction from an inlet of the passage (64) to an outlet of the passage (64).

10. Injection system according to any one of claims 1 to 9, wherein the annular socket beak (76) is formed by an upstream free end of the socket (52).

11. Injection system according to any one of claims 1 to 10, wherein the annular injector nozzle (72) takes the form of a collar (72A) extending radially outwardly from the outer surface (68) of the fuel injector nose (54) and terminating in an annular rim (72B) extending in one or the direction from the inlet of the passage (64) to the outlet of the passage (64), to a free end of the annular injector nozzle (72).

12. Turbomachine for aircraft, comprising a combustion chamber (18) and at least one injection system (42) according to any one of claims 1 to 11 for supplying the combustion chamber with a mixture of air and fuel.

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