FR3083823A1 - FUEL INJECTION SYSTEM OF A CONSTANT VOLUME COMBUSTION SYSTEM FOR A TURBOMACHINE - Google Patents

Abstract

A constant volume combustion system (1) for a turbomachine comprising a plurality of combustion chambers (2) distributed annularly about a main axis (θ), said combustion chambers (2) comprising intake orifices ( 21) and exhaust ports (22), the system (1) comprising a selector (3) movable in rotation about the main axis (θ) which is configured to selectively block and open the intake ports (21 ) and the exhaust ports (22) during the rotation of said selector (3), characterized in that at least one fuel injection channel (34) is formed in said selector (3) to selectively inject the fuel in the combustion chambers (2) during the rotation of said selector (3).

Description

Invention background

The present invention relates to the field of combustion chambers of aircraft turbomachines, of the constant volume combustion type.

The invention applies to any type of turbomachinery, in particular to turbojets, turbopropellers, and turbomachines with non-faired fans, also known by the English term "Open Rotor".

A conventional aircraft turbomachine comprises, in known manner, one or more combustion chambers. Such a combustion chamber is supplied with pressurized air by a compressor module and it comprises a fuel injector which is capable of injecting fuel into the admitted air flow to burn it and thus cause the emission of hot gases which are used to drive a turbine, which in turn drives the compressor module and which can also drive a fan of the turbomachine.

In such a chamber, the fuel flow is continuous and the combustion operates according to a so-called Brayton cycle, that is to say according to a combustion cycle at constant pressure or "CPC". However, to obtain specific consumption gains, it has been envisaged to replace the combustion chamber operating according to a Brayton cycle by a plurality of combustion chambers operating according to a Humphrey cycle, that is to say according to a cycle. constant volume combustion or "CVC".

Document WO 2016/120551 describes, for example, a constant volume combustion system comprising combustion chambers arranged around an axis, each chamber comprising a compressed gas intake port and a burnt gas exhaust port, and a rotary intake / exhaust valve. Each intake / exhaust port is configured to be opened or closed by the rotary intake / exhaust valve.

To ensure proper operation of the combustion system at constant volume, fuel injection must be precise and controlled. In particular, the fuel injection should preferably be cut off during the intake and exhaust phases.

Document FR 17 55765 (filing number) is also known, which describes a constant volume combustion system in which the injection of fuel into the combustion chambers is carried out by injectors arranged in each of the combustion chambers. Piloting the injection is thus achieved by piloting each of the injectors located in each of the chambers.

However, such a fuel injection solution has several drawbacks. On the one hand, this solution encounters a problem of risk of coking of the fuel, of the fuel stagnating in the injectors which are located in the combustion chambers. On the other hand, this solution described in the document FR 17 55765 encounters a problem of a mass and a large bulk.

Subject and summary of the invention

The object of the invention is in particular to provide a CVC constant volume combustion system having a fuel injection device allowing precise and controlled injection.

In addition, the invention aims to reduce the size and weight of the fuel injection device.

The invention also aims to limit the risk of coking of the fuel.

In addition, the invention aims to provide a fuel injection device which has a simple structure.

According to a first aspect, the invention provides a constant volume system for a turbomachine comprising a plurality of combustion chambers annularly distributed around a main axis, said combustion chambers comprising intake orifices and exhaust, the system comprising a selector movable in rotation about the main axis which is configured to selectively block and open the intake orifices and the exhaust orifices during the rotation of said selector, characterized in that at least one fuel injection channel is formed in said selector to selectively inject fuel into the combustion chambers during rotation of said selector.

Thus, thanks to said at least one injection channel formed in the selector, said selector fulfills the function of injecting fuel into the combustion chambers in addition to the function of opening and closing the intake orifices and d exhaust from the combustion chambers, thus increasing the compactness of the combustion system at constant volume.

In addition, the fuel injection being carried out by the at least one injection channel formed in the selector, the fuel does not stagnate inside the combustion chamber, thus reducing the risk of coking with respect to an injector of fuel located in each combustion chamber.

The constant volume combustion system can also include any of the following characteristics, taken alone or in combination depending on the technical possibilities:

the selector comprises an external ferrule on which at least one intake port and at least one exhaust port are formed which are configured to cooperate respectively with the intake ports and the exhaust ports when the selector is rotated, a plurality of fuel injection nozzles being located on the outer shell for injecting fuel into the combustion chambers via the intake and / or exhaust ports, said plurality of fuel injection nozzles being connected said at least one fuel injection channel;

the plurality of fuel injection nozzles are angularly offset from said at least one intake lumen and said at least one exhaust lumen;

the selector is mounted so that it can rotate about a fixed fuel distributor, said fuel distributor comprising distribution orifices distributed around the contour of said fuel distributor which communicate with a central cavity and which are configured to cooperate with said at least one selector fuel injection channel to allow fuel flow from the fuel distributor to the fuel injection channel;

a bearing is arranged between the fuel distributor and the selector, on either side of the distribution orifices, a seal being located between each bearing and the distribution orifices;

a seal is arranged between the fuel distributor and the selector, on either side of the distribution orifices, a bearing being located between each seal and the distribution orifices;

the dispensing orifices are formed by radial holes of oblong shape directed perpendicular to the main axis;

the system includes a source of pressurized fuel which is connected to the central cavity of the fuel dispenser.

According to a second aspect, the invention proposes a turbomachine comprising a system according to any one of the preceding characteristics.

In addition, according to one possible characteristic, the turbomachine has a maximum thrust less than or equal to 700daN.

According to a third aspect, the invention proposes an aircraft comprising a turbomachine according to any one of the preceding characteristics.

Brief description of the drawings

Other characteristics and advantages of the invention will emerge from the following description of particular embodiments of the invention, given by way of nonlimiting examples, with reference to the appended drawings, in which:

FIG. 1 represents a combustion system at constant volume for a turbomachine according to a possible embodiment;

FIG. 2 represents a section of the system illustrated in FIG. 1 during a combustion phase;

FIG. 3 represents a section of the system illustrated in FIG. 1 during an exhaust phase;

FIG. 4 represents a section of the system illustrated in FIG. 1 according to a plane passing through the intake orifices of the combustion chambers;

FIG. 5 represents a section of the system illustrated in FIG. 1 according to a median plane;

FIG. 6 represents a section of the system illustrated in FIG. 1 along a plane passing through the exhaust orifices of the combustion chambers;

FIG. 7 represents an isolated view of the selector of the system illustrated in FIG. 1;

FIG. 8 represents an isolated view of the combustion chambers of the system illustrated in FIG. 1;

FIG. 9 represents a schematic view of the cooperation between the fuel injection channels of the distributor on the one hand with the orifices of the combustion chambers and on the other hand with the distribution orifices of the fuel distributor, during rotation said distributor.

Detailed description of embodiments

As illustrated in FIG. 1, a constant volume combustion system 1 for a turbomachine comprises a plurality of combustion chambers 2 which are annularly distributed around a main axis Θ, which corresponds with the axis of the turbomachine. The combustion chambers 2 are fixed and thus form a stator of the combustion system 1 at constant volume.

The constant volume combustion system 1 is located in the turbomachine between a compressor and a turbine.

As visible in FIG. 8, each combustion chamber 2 comprises an inlet orifice 21 and an exhaust orifice 22 which are located on the internal annular contour of said combustion chambers 2.

Each combustion chamber 2 of system 1 follows a cycle of different phases during the operation of the turbomachine. The cycle includes an intake phase during which air from the compressor enters the combustion chamber, then a combustion phase during which the air is burned with fuel, then finally an exhaust phase during which l burnt air escapes from the combustion chamber towards the turbine.

The constant volume combustion system 1 also includes a selector 3 which makes it possible to control the admission of air coming from the compressor and the exhaust of the air following combustion towards the turbine for the combustion chambers 2.

The selector 3 is formed by a wheel movable in rotation about the main axis Θ, so as to form the rotor of the system 1. The selector 3 is configured to selectively open and close the intake orifices 21 and the orifices exhaust 22 of the combustion chambers 2 during the rotation of said selector 3. By opening and selectively closing the intake ports 21 and the exhaust ports 22, it is understood here that the intake ports 21 and the exhaust ports 22 are open and closed one after the other during the rotation of the selector 3.

As can be seen in FIG. 7, the selector 3 comprises at least one intake port 31 and at least one exhaust port 32 formed on an external shell 33. In the exemplary embodiment, the selector 3 comprises a plurality of ports d intake 31 and a plurality of exhaust lights 32.

The intake ports 31 are configured to cooperate with the intake ports 21 so that, on the one hand, the intake ports are open when they are located opposite an intake port during the phase d intake, and on the other hand the intake ports 21 are closed by the outer shell 33 of the selector 3 when said intake ports 31 are angularly offset with respect to the intake ports 31 and thus are not located opposite an intake light 31 during the other phases.

Thus, when during its rotation the selector 3 places an intake light 31 opposite the intake orifice 21 of a combustion chamber 2, the intake phase of said combustion chamber 2 begins and the air from the compressor enters said combustion chamber 2 via the intake port 31 and the intake port 21.

The exhaust ports 32 are configured to cooperate with the exhaust ports 22 so that on the one hand the exhaust ports 22 are open when they are located opposite an exhaust port 32 during the exhaust phase, and on the other hand the exhaust ports 22 are closed by the outer shell 33 of the selector 3 when said exhaust ports 22 are angularly offset relative to the exhaust ports 32 and thus are not located opposite an exhaust light 32 during the other phases.

Thus, when during its rotation the selector 3 places an exhaust light 32 opposite the exhaust orifice 22 of a combustion chamber 2, the exhaust phase of said combustion chamber 2 begins and the air burnt gas escapes from said combustion chamber 2 via the exhaust port 22 and the exhaust port in the direction of the turbine.

As shown in FIG. 7, the intake lights 31 and the exhaust lights 32 are axially offset along the main axis Θ, so that the intake lights 31 and the exhaust lights 32 have circular paths with the rotation of the selector 3 offset axially.

In addition, as illustrated in FIG. 7, the arrangement of the intake lights 31 and the exhaust lights 32 on the outer shell 33 may include an angular overlap. That is to say that the same combustion chamber 2 can comprise its intake orifice 21 facing an intake lumen 31 and at the same time include its exhaust orifice 22 opposite a lumen exhaust 32. The intake phase and the exhaust phase can thus overlap. For example, the fact that a new intake phase begins before the end of the exhaust phase makes it possible to improve the exhaust of the combustion gases towards the turbine, these combustion gases being expelled by the admission of the air from the compressor.

As shown in FIG. 2, for the injection of fuel inside the combustion chambers 2 during the combustion phase, the selector 3 comprises at least one fuel injection channel 34 which is configured to selectively inject the fuel in said combustion chambers 2 during the rotation of said selector 3. In the embodiment illustrated in the figures, the selector 3 comprises a plurality of fuel injection channels 34.

By selective fuel injection, it is understood here that fuel is injected into the combustion chambers 2 one after the other as the selector 3 rotates via the fuel injection channels 34.

The selector 3 also comprises fuel injection nozzles 35 which are located on the outer shell 33 of said selector 3, said fuel injection nozzles 35 being connected to the fuel injection channels 34. The injection nozzles of fuel 35 are formed by holes in the outer shell 33.

The fuel injection nozzles 35 are configured to cooperate with the intake ports 21 and / or the exhaust ports 22 and inject the fuel into the combustion chambers 2 through said intake ports 21 and / or the exhaust ports 22. In the embodiment illustrated in the figures, the fuel injection nozzles 35 are configured to cooperate with the intake ports and the exhaust ports 22. The fuel injection nozzles 35 are thus located on the outer shell 33 so as to be axially aligned with the intake ports 21 and the exhaust ports 22, thus allowing the fuel injection nozzles 35 to be opposite the intake ports 21 and exhaust ports 22 during the combustion phase.

The fact that the injection nozzles 35 are distributed over the outer shell 33 so that said injection nozzles 35 are located opposite the intake orifices 21 and opposite the exhaust orifices 22 makes it possible to provide an injection fuel both via the intake orifice 21 and the exhaust orifice 22 of each combustion chamber 2, thus making it possible to improve the homogeneity of the injection of the fuel into said combustion chamber. Furthermore, in order to further improve the homogeneity of the fuel injection, the same number of injection nozzles 35 inject fuel through the intake port 21 as through the exhaust port 22.

In addition, the fuel injection nozzles 35 are angularly offset from the intake lights 31 and the exhaust lights 32, so as not to inject fuel into the combustion chambers 2 when the intake lights 31 and the exhaust ports 32 are respectively aligned with the intake ports 21 and the exhaust ports 22. In other words, the fuel injection nozzles 35 cannot be opposite an intake port 21, or an exhaust port 22, when said intake port 21, or said exhaust port 22, is located opposite an intake light 31, or an exhaust light 32. Thus , the fuel is injected only during the combustion phase, and not during the intake and exhaust phases.

As shown in Figures 2 and 3, the system 1 also includes a fuel distributor 4 around which the selector 3 is rotated, said fuel distributor 4 being fixed so as to form a portion of the stator of said system 1. The distributor of fuel 4 makes it possible to supply fuel to the fuel injection channels 34 of the selector 3.

The fuel distributor 4 comprises a central cavity 41 and distribution orifices 42 distributed over the contour of the fuel distributor 4 and which communicate with the central cavity 41. The distribution orifices 42 are configured to cooperate with the injection channels of fuel 34 in order to allow fuel to flow from the central cavity 41 of the distributor to the fuel injection channels 34. The distribution orifices 42 are thus located opposite the intake orifices 21 and the exhaust orifices 22 of the combustion chambers 2, so that when the injection channels 34 come opposite the intake orifices 21 and the exhaust orifices 22 during the rotation of the selector 3, the fuel injection channels 34 also arrive in view of the distribution orifices 42, and thus said fuel injection channels 34 connect the fuel distributor 4 to the combustion chambers 2.

The cooperation between the distribution orifices 42 of the fuel distributor 4 and the fuel injection channels 34 is illustrated in FIGS. 2 and 3. In FIG. 2, the two combustion chambers 2 located on the section plane are in their combustion phase, and thus a fuel injection channel 34 connects each of these two combustion chambers 2 to a distribution orifice 42. In FIG. 3, the two combustion chambers 2 are in their exhaust phase, and thus the two combustion chambers 2 are not connected by a fuel injection channel 34 to a distribution orifice 42.

FIG. 9 schematically illustrates the cooperation of the injection channels 34 and on the one hand the intake orifices 21 of the combustion chambers 2, and on the other hand the distribution orifices 42 of the distributor

4. As can be seen in FIG. 9, the distribution orifices 42 are located opposite the intake orifices 21 (and also the exhaust orifices 22). The arcs of a circle identified by the symbol "O" correspond to portions of the trajectory on which the fuel injection channels 34 inject fuel into the combustion chambers 2, while the arcs of a circle identified by the symbol "X" correspond to portions of the trajectory on which the fuel injection channels 34 do not inject fuel into the combustion chambers 2.

FIG. 9 being produced according to a cutting plane passing through the intake orifices 21 of the combustion chambers, the cooperation between the fuel injection channels 34 and the exhaust orifices 22 is not visible. The cooperation between the fuel injection channels 34 and the exhaust ports 22 is however similar to the cooperation between said fuel injection channels 34 and the intake ports 21.

The dispensing orifices 42 are advantageously formed by radial holes which have an oblong shape, said oblong shape being perpendicular to the main axis Θ. In other words, the oval formed by the oblong holes which form the distribution orifices 42 is directed perpendicular to the main axis Θ. Such an oblong shape ensures longer cooperation between the fuel injection channels 34 and the distribution orifices 42.

A source of pressurized fuel is connected to the central cavity 41 of the fuel distributor 4. The fuel source can for example be formed by a fuel tank and an injection pump.

Furthermore, the system 1 comprises two bearings 5, for example ball bearings or roller bearings, which are located between the selector 3 and the fuel distributor 4 in order to form the pivot connection. In addition, the bearings 5 are located on either side of the distribution orifices 42. In addition, the system 1 comprises seals 6, at least one seal 6 being located between each bearing 5 and the distribution orifices 42. The seals 6 thus limit fuel leakage to bearings 5.

Furthermore, according to another possible variant which is advantageous when the lubrication is carried out by the fuel, the bearings 5 are each located between a seal 6 and the distribution orifices 42. The seals 6 make it possible to prevent the fuel from going to the beyond the bearings 5.

The constant volume combustion system 1 is particularly advantageous for a small propulsion, that is to say a turbomachine with a maximum thrust less than or equal to 700daN, for example equal to 500daN. The system 1 is indeed compact, the selector 3 fulfilling the dual function of opening and closing the intake 21 and exhaust 22 orifices of the combustion chambers 2, and of injecting fuel into said combustion chambers 2.

Claims (11)

1. A constant volume combustion system (1) for a turbomachine comprising a plurality of combustion chambers (2) distributed annularly about a main axis (Θ), said combustion chambers (2) comprising intake orifices (21) and exhaust ports (22), the system (1) comprising a selector (3) movable in rotation about the main axis (0) which is configured to selectively block and open the intake ports ( 21) and the exhaust orifices (22) during the rotation of said selector (3), characterized in that at least one fuel injection channel (34) is formed in said selector (3) for selectively injecting the fuel in the combustion chambers (2) during the rotation of said selector (3). 2. System (1) according to claim 1, in which the selector (3) comprises an external ferrule (33) on which is formed at least one intake lumen (31) and at least one exhaust lumen (32) which are configured to respectively cooperate with the intake orifices (21) and the exhaust orifices (22) during the rotation of the selector (3), a plurality of fuel injection nozzles (35) being located on the outer shell (33) for injecting fuel into the combustion chambers (2) via the intake ports (21) and / or the exhaust ports (22), said plurality of fuel injection nozzles (35) being connected to said at least one fuel injection channel (34). 3. System (1) according to claim 2, wherein the plurality of fuel injection nozzles (35) is angularly offset with respect to said at least one intake light (31) and said at least one light '' exhaust (32). 4. System (1) according to any one of claims 1 to 3, wherein the selector (3) is rotatably mounted around a fixed fuel distributor (4), said fuel distributor (4) comprising distribution orifices (42) distributed around the contour of said fuel distributor (4) which communicate with a central cavity (41) and which are configured to cooperate with said at least one fuel injection channel (34) of the selector (3 ) to allow fuel to flow from the fuel distributor (4) to the fuel injection channel (34). 5. System (1) according to claim 4, wherein a bearing (5) is disposed between the fuel distributor (4) and the selector (3), on either side of the distribution orifices (42), a seal (6) being located between each bearing (5) and the distribution orifices (42). 6. System (1) according to claim 4, in which a seal (6) is disposed between the fuel distributor (4) and the selector (3), on either side of the distribution orifices (42), a bearing (5) being located between each seal (6) and the dispensing orifices (42). 7. System (1) according to any one of claims 4 to 6, wherein the dispensing orifices (42) are formed by radial holes of oblong shape directed perpendicular to the main axis (Θ). 8. System (1) according to any one of claims 4 to 7, wherein said system (1) comprises a source of pressurized fuel which is connected to the central cavity (41) of the fuel distributor (4). 9. Turbomachine comprising a system (1) according to any one of claims 1 to 8. 10. The turbomachine according to claim 9, in which said turbomachine has a maximum thrust less than or equal to 700daN. 11. An aircraft comprising at least one turbomachine according to claim 9 or claim 10.