FR3083288A1 - PISTON DISCHARGE VALVE WITH INTERNAL CONDUIT - Google Patents

Abstract

Discharge valve (30) for a turbomachine (10), comprising a fixed housing (31) defining an internal duct and connected to an air inlet and an air outlet, a movable member (34) between at least two positions, respectively of opening and closing of said conduit, an annular space (44) to said housing (31), configured to be supplied with pressurized gas (42) in order to move said member (34) between its two positions. Said movable member (34) comprises a tubular portion which internally delimits a discharge air flow passage (32), and which is surrounded by said annular space (44).

Description

INTERNAL CONDUIT PISTON DISCHARGE VALVE

TECHNICAL FIELD The present invention relates to a relief valve for a turbomachine in particular of an aircraft.

STATE OF THE ART [0002] A double-flow turbomachine comprises a flow stream for a primary flow (or hot flow) and a flow stream for a secondary flow (or cold flow). It is known to equip such a turbomachine with relief valves, sometimes designated by their English acronym VBV (Variable Bleed Valve) or called air valves (because they open or close air ducts). These are conventionally all-or-nothing valves (closed or open).

Conventionally and well known per se, and as illustrated in FIG. 1 which is a schematic view in axial section of a twin-body turbojet engine 10, such a turbojet engine generally comprises from upstream to 'downstream in the direction of gas flow, a low pressure compressor 12, a high pressure compressor 14 (core HP), a combustion chamber 16, a high pressure turbine 18 and a low pressure turbine 20, which define a vein d flow of a primary flow 22 of gas and form the central compartment 15 (to be identified in FIG. 1) (“core zone”) of the turbojet engine. In the case of turbofan engines, the turbojet engine further comprises a fan 24 streamlined by a nacelle 26 to generate a secondary flow 28 passing through an annular secondary flow stream, defined between the nacelle 26 and the central compartment 15 of the turbojet engine.

The pressure P | in the primary flow stream and greater than the pressure Pu in the secondary flow stream.

The relief valves 30 are conventionally located in the central compartment 15 ("core zone") of the turbomachine, more particularly near a compressor, and are intended to regulate the air inlet flow rate in the primary stream in particular in order to limit the risks of pumping of the compressor of the turbomachine by allowing the evacuation or the discharge of an air flow in the secondary stream.

Pumping is an aerodynamic phenomenon well known to any person skilled in the art, operating in a compressor: when the pressure difference between the inlet and the outlet of the compressor is too high, instabilities (called separations) appear at the level of the compressor blades. If this detachment phenomenon is too great, the flow of gas generated in the compressor no longer makes it possible to push said gas in the right direction, and the "high pressure" part of the compressor (the outlet) empties in its "low" part pressure >> (entry). In some extreme cases, an inversion of the direction of flow can be observed.

The pumping phenomenon reduces the performance of the compressors, and can also be destructive to the blades of the compressor.

Pumping is one of the most serious problems that a pilot may have to face, because it occurs quite generally when the aircraft takes off.

Furthermore, in the event of accidental penetration into the primary stream of water, in particular in the form of rain or hail, or else various debris which is liable to harm the operation of the turbomachine, these valves make it possible to recover this water or these debris which are then centrifuged and conveyed to the secondary vein to be ejected.

[0010] Thus, each aeronautical engine is provided with systems for unloading the compressor in the form of valves conventionally actuated by electro-pneumatic actuators.

Conventionally, the discharge valves are all-or-nothing valves with electro-pneumatic actuation, and are today all built on the same scheme: a piston in the center of a fixed housing around which air flows when the valve is open. When the valve is open, the outer walls of the valve heat up considerably and reach the temperature of the air entering the valve (the air coming from the primary vein), i.e. 300-500 °. This results in radiation in the compartment where the valve is placed and this makes it very difficult to attach to the relief valve, an electropneumatic actuator provided with a solenoid valve to control it.

It would be possible to insert a thermal wedge between the discharge valve and its solenoid valve, but this solution is not reliable because the thermal wedges degrade over time.

Thus, the commonly used solution is that the valves are fixed in the central compartment of the turbomachine but are controlled by dedicated equipment, called a controller, placed in the cold zone, for example in the fan compartment. This avoids any thermal problem and avoids exceeding the operating temperature limit of the solenoid valve of the electro-pneumatic actuator of the controller.

However, this distance can cause inaccuracies in the control and requires long fluid lines (here air lines) which can be bulky and in which condensation phenomena are observed.

The present invention provides a solution to this problem.

STATEMENT OF THE INVENTION For this purpose, the present invention provides a discharge valve for a turbomachine, comprising

- a fixed box defining an internal duct and connected to an air inlet and an air outlet,

- a movable member between at least two positions, respectively of opening and closing of said duct,

- an annular space in said housing, configured to be supplied with gas under pressure for the movement of said member between its two open and closed positions, characterized in that said movable member comprises a tubular portion which internally delimits a flow passage of discharge air, and which is surrounded by said annular space.

The gas present in the annular space makes it possible to isolate the walls of the fixed housing from the hot discharge air. This therefore makes it possible to prevent the intense heating of the walls of the external housing and to keep them at an average temperature.

The device according to the invention may include one or more of the following characteristics, taken in isolation from one another or in combination with each other:

the tubular portion may include a cylindrical part and a frustoconical part,

the movable member may comprise a central bulb with an aerodynamic profile, connected to a wall of the movable member by an annular row of arms,

the movable member may comprise a central bulb with an aerodynamic profile, connected to a wall of the movable member by a grid,

- the central bulb can be connected to the wall of the frustoconical part of the movable member,

the central bulb can be configured to cooperate with an annular seat of said housing with a view to sealing said channel,

- The movable member can be provided with sealing means between the longitudinal ends of the tubular portion of the movable member and the housing.

The invention also relates to a discharge device comprising a valve as described above, characterized in that it comprises an electro-pneumatic actuator fixed to the valve housing.

The electro-pneumatic actuator can be fixed to the housing at the level of the annular space.

The present invention finally has a third object, a turbomachine comprising a device as described above.

DESCRIPTION OF THE FIGURES

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

FIG. 1 is a schematic view in axial section of a double-body turbojet engine,

FIG. 2 is a diagrammatic view of a longitudinal section of a relief valve according to the state of the art and of an associated electropneumatic actuator, the valve being in the closed position,

- Figure 3 is a schematic view of a longitudinal section of the valve of Figure 2 in the open position,

FIGS. 4a and 4b are diagrammatic views of 3/4 and front longitudinal sections respectively of a relief valve according to the invention in the closed position, and

- Figures 5a and 5b are schematic views of longitudinal sections similar to Figures 4a and 4b in which the valve is in the open position.

DETAILED DESCRIPTION As can be seen in FIG. 2, a valve 30 according to the state of the art has a fixed housing 31 of general cylinder shape, of axis of revolution X. The valve 30 extends substantially radially with respect to to the longitudinal axis of the turbomachine 10, between the primary flow circulation stream 22 (in which there is a pressure P |) and the secondary flow circulation stream 28 (in which there is a pressure Pu). The pressure Pu is less than the pressure P |.

The housing 31 includes a cavity 32 open at the two ends of the housing 31, making it possible to connect the two primary and secondary flow circulation veins 22, 28. The valve 30 according to the state of the art, has a distal end 30D opening into the secondary vein 28 forming an air outlet, and a proximal end 30P opening into the primary vein 22 forming an air inlet. When the valve 30 is open (see FIG. 3, for example), the proximal end 30P and the distal end 30D are placed in fluid communication: the two primary and secondary flow circulation veins 22, 28 are therefore also put in fluid communication and the air leaves the primary vein 22 to go into the secondary vein 28 due to the pressure difference (since Pu <Pi).

A movable member 34 (here a valve) movable in translation along the axis X is housed in the cavity 32. This movable member 34 is of generally cylindrical shape and allows to close, if necessary, the valve 30 by cooperating with a bottleneck of the cavity 32. The movable member 34 is linked to a return means (here surrounded by a return spring) 36 which, when it relaxes, opens the valve 30.

When the valve 30 is in the open position, the discharge air circulates around the movable member 34, as visible in FIG. 3.

When the valve 30 is in the closed position (see Figure 2), the two primary and secondary veins 22,28 are isolated.

The valve 30 opens with a translation of the movable member 34 towards the distal end 30D of the valve 30.

The movable member 34 forming a valve has an elongated shape of revolution. This movable member 34 comprises a proximal part constituting the seat of the valve cooperating with the bottleneck of the cavity 32, and a distal part constituting a piston, the two ends being connected by a rod. Said piston slides in an internal central cavity of the housing 31. The piston thus separates the internal central cavity into two internal chambers, the lower internal chamber 37 and the upper internal chamber 39.

The upper internal chamber 39 has an opening 38 opening onto a channel connected to an air outlet port of an electro-pneumatic "actuator controller" 40.

The controller-actuator 40 can take two configurations: an opening configuration of the valve 30 and a closing configuration of the valve 30. The controller-actuator 40 allows, by changing configuration, to open or close the valve 30 by modifying the balance of pressures within it. The change in configuration of the controller-actuator 40 is induced by a solenoid valve 41 comprising at least one electric coil E.

When the controller-actuator 40 is in the closed configuration of the valve 30, pressurized gas (control gas, here air) 42 is sent into the channel, towards the opening 38 and there is a control pressure Pc in the upper internal chamber 39. This pressure Pc is greater than the pressure of the lower internal chamber 37, close to the pressure P _N of the secondary flow flow stream 28, and the valve 30 is maintained in closed position. This is the configuration illustrated in Figure 2.

When the controller-actuator 40 is in the opening configuration of the valve 30 (not shown), there is no more control gas 42 sent to the opening 38, and the upper internal chamber 39 is found at P _atm . As the pressure of the lower internal chamber 37 is greater than P _am b (because equal to Pi when the valve 30 is in the open position), the spring 36 expands and the valve 30 opens. It is the configuration of figure 3.

As mentioned above, the distance between the discharge valve 30 and the controller-actuator 40 is large and can be a source of problems.

Thus, the present invention proposes in particular to modify the valve 30 in order to allow the controller-actuator 40 to be attached to it and to reduce this distance.

According to the invention, the fixed housing 31 defines an internal conduit, and the movable member 34 of the valve 30 according to the invention is no longer a movable valve in the center of the cavity 32, but a crown (or tubular portion) internally defining a discharge air flow passage 32 through which the air discharged from the primary flow circulation vein 22 flows towards the secondary flow circulation vein 28.

As shown in Figures 4a, 4b, 5a and 5b, the tubular portion of the movable member 34 is formed of two parts: a distal cylindrical part and a proximal frustoconical part. Thus, the diameter of the movable member 34 increases towards the proximal end 30P of the valve 30. This makes it possible to free an annular space 44 between a wall 46 of the movable member 34 and a wall 48 of the valve 30 This annular space 44 surrounds the air flow passage 32 and forms an isolation zone.

As shown in Figures 4a and 4b and similar to the description of Figure 2, the valve 30 is in the closed position when the movable member 34 is held towards the proximal end 30P of the valve, the spring 36 being compressed.

The movable member 34 is held towards the proximal end 30P by the control air inlet 42 to P _c in the annular space 44 via the orifice 38 placed in the wall 48 of the valve 30. This control air 42 exerts pressure on the wall 46 of the frustoconical part of the movable member 34 and keeps the valve 30 in the closed position, the pressure Pc being greater than the pressure P | of the primary flow flow stream 22.

The fact that the movable member 34 has a proximal frustoconical part therefore allows the application of a pressure Pc for closing the valve 30 on the movable member 34 and to reinforce the insulating characteristic of the space ring finger 44.

The annular space 44 thus makes it possible to form a cooling zone and makes it possible to place the controller-actuator 40 and its solenoid valve 41 in contact with the valve 30 while ensuring that it is kept at a temperature below the limit temperature despite the engine environment at high temperature and the passage of hot air in the valve 30 when the latter is in the open position.

Placing the controller-actuator 40 in contact with the valve 30 allows a very significant gain in mass of the pneumatic system. In addition, there is a functional gain because the entire control chain of valve 30 (including the solenoid valve 41 of the controller-actuator 40) is on the same equipment, which simplifies troubleshooting and maintenance exchanges.

More specifically, the valve 30 is closed by a central bulb 50 connected to the wall 46 of the movable member 34 by arms 52 extending radially in the discharge channel 32. In another mode of embodiment (not shown), the arms 52 can be replaced, for example, by a grid. We can also consider that the arms 52 constitute a grid having a very wide pitch.

When the valve 30 is in the closed position, the bulb 50 cooperates and rests on a seat 54 and there is a metal-metal contact ensuring a very good seal. The concentricity of the association “bulb 50 - seat 54” is ensured by annular guide means also ensuring sealing (here two guide rings serving as seals) 56, 58 located between the wall 46 of the movable member 34 and the wall 48 of the valve 30.

The valve 30 closes from the bottom, which makes it possible to have a valve 30 cooled in the closed position. The "bulb 50 - seat 54" association is sealed at the inlet of the valve 30 in the direction of flow of the discharge flow, on the proximal side 30P. The area upstream of this seal is substantially at the temperature of the air in the primary flow 22, therefore very hot (because there are air recirculation phenomena). The area downstream of this seal is substantially at the temperature of the air in the secondary flow 28 (therefore rather cold). In the present configuration, it can be seen that the annular space 44 (and therefore the electropneumatic controller-actuator 40) is downstream of the seal. Thus, this annular space 44 is in a cold atmosphere when the valve 30 is in the closed position. This is important because this type of relief valve 30 is almost always in the closed position during operation of the turbomachine and this therefore makes it possible to keep it at low temperature.

As shown in Figures 5a and 5b, in the absence of pressure P _c induced by the control air inlet 42, the pressure P | at the proximal end of the passage 32 of the valve 30, combined with the force of the spring 36, pushes and naturally lifts the movable member 34 and the valve 30 opens.

The shape of the bulb 50, as well as the possible presence of a deflector (shown in Figure 5b by a grid 60) downstream of the seat 54 of the valve 30, can limit the turbulence of the air flow when the valve 30 is in the open position and the two primary and secondary flow circulation streams 22, 28 are placed in fluid communication.

The spring 36 allows here to open the valve 30 in the absence of pressure in the system (for example when all the pressures are equal, when the turbomachine 10 is stopped).

Claims (10)

1. Discharge valve (30) for a turbomachine (10), comprising: - a fixed housing (31) defining an internal duct and connected to an air inlet and an air outlet, - a movable member (34) between at least two positions, respectively of opening and closing of said conduit, - an annular space (44) to said housing (31), configured to be supplied with pressurized gas (42) for the movement of said member (34) between its two positions, characterized in that said movable member (34) comprises a tubular portion which internally defines an air flow passage (32) for discharge, and which is surrounded by said annular space (44). 2. Valve (30) according to the preceding claim, wherein the tubular portion comprises a cylindrical part and a frustoconical part. 3. Valve (30) according to any one of the preceding claims, in which the movable member comprises a central bulb (50) with aerodynamic profile, connected to a wall (46) of the movable member (34) by a row arm ring (52). 4. Valve (30) according to any one of claims 1 and 2, wherein the movable member comprises a central bulb (50) with aerodynamic profile, connected to a wall (46) of the movable member (34) by a grid. 5. Valve (30) according to any one of claims 2 to 4, wherein the central bulb (50) is connected to the wall of the frustoconical part of the movable member (34). 6. Valve (30) according to any one of claims 4 and 5, wherein the central bulb (50) is configured to cooperate with an annular seat (54) of said housing for the sealed closure of said channel (32). 7. Valve (30) according to any one of the preceding claims, in which the movable member is provided with sealing means (56, 58) between the longitudinal ends of the tubular portion of the movable member (34) 5 and the housing (31). 8. Discharge device comprising a valve (30) according to any one of the preceding claims, characterized in that it comprises an electro-pneumatic controller-actuator (40) fixed to the housing 10 (31) of the valve (30). 9. Device according to the preceding claim, in which the electro-pneumatic controller-actuator (40) is fixed to the housing at the level of the annular space (44). 10. Turbomachine (10) comprising a device according to any one of claims 8 and 9.