ELECTROHYDRAULIC SYSTEM FOR CONTROLLING THE ANGULAR POSITION OF THE PROPELLER OF A SAILING TURBO MACHINE

Description

DOMAINE TECHNIQUE GENERAL

[0001] The invention relates to the field of turbomachines comprising a variable-pitch propeller or fan. More specifically, the invention relates to a system for actuating the pitch of a propeller or fan of such a turbomachine. ETAT DE L'ART

[0002] Different turbomachine architectures use a variable-pitch propeller (turboprop, open rotor) or fan (turbojet). This variability allows the turbomachine to adapt to variable flight conditions by maintaining a favorable air angle of incidence on the blades. Pitch variability is particularly necessary for rotors with a low compression ratio, such as turboprop propellers and turbomachine fans with a high bypass ratio (ratio between the flow rate of the secondary (cold) flow and the flow rate of the primary flow (which passes through the primary body)).

[0003] Multiple pitch change mechanisms have been devised to vary the pitch of propeller or fan blades. These mechanisms generally involve rotating the blade around its main axis by means of kinematics, for example a connecting rod-eccentric assembly actuated by a cylinder. The cylinder is supplied with hydraulic fluid (for example oil) from a lubrication unit of the turbomachine, the variation of the delivered hydraulic fluid pressure as well as the distribution of the fluid in one or other of the cylinder chambers make it possible to vary the pitch of the blades.In order to transfer the hydraulic fluid supply of the pitch change mechanism from a fixed reference (lubrication unit) of the turbomachine to a rotating reference (of the fan), an OTB (an acronym for Oil Transfer Bearing, for multi-passage rotating hydraulic seal or rotating oil transfer) is generally used. In a manner known per se, the OTB comprises a part fixed relative to a stator part of the turbomachine and which is connected, via dedicated pipes, to a servovalve and a pump, itself connected to the engine lubrication circuit comprising the lubrication unit and an oil reservoir and a pump, and a rotating part which is integral in movement with a rotor part of the turbomachine.However, the OTB is a complex and fragile device, likely to generate malfunctions, including significant oil leaks affecting the reliability and performance of the turbomachine and requiring the installation of recovery pumps and oversizing of the engine oil system. The pressurized oil supply of this device is always problematic, because in general to provide a high power density, hydraulic pumps driven by one of the turbomachine shafts are used. Furthermore, this configuration has operating limitations at low speeds since it is dependent on the speed of the high-pressure body of the turbomachine and can be subject to overcharging problems during certain maneuvers since it is dependent on the supply of the engine oil circuit.For example, when the turbomachine is close to stopping (during shutdown, during start-up, or stopped) it may be necessary to either actuate or maintain the pitch setting, which generally requires the use of an additional independent pump (usually electrically powered), and a pitch lock device. Finally, this configuration requires a system to protect against blade pitch closing in flight due to hydraulic failure. Other alternatives include a pitch lock system or a counterweight system to ensure blade feathering (opening of the pitch to limit drag). Both systems are heavy, complex, expensive, and can generate other failures such as untimely pitch locking.

[0004] Furthermore, since the operation of the lubrication unit is generally linked to the operation of the turbomachine, it is necessary to provide auxiliary systems to ensure certain protection functions, particularly in the event of overspeed or engine shutdown. It is therefore necessary to provide a functional feathering system even in the absence of hydraulic fluid pressure.

[0005] On the other hand, the pitch change mechanism must be able, with the engine stopped, to ensure exit from the flag position.

[0006] Document US 2020 / 096015 describes a device for regulating a hydraulic machine by means of constant displacement pumps driven with a variable rotation speed. PRESENTATION DE L'INVENTION

[0007] An object of the invention is to propose a variable timing turbomachine which overcomes the disadvantages of the prior art mentioned below.

[0008] Another object of the invention is to propose an independent pitch change mechanism which overcomes the difficulties linked to the transfer of hydraulic fluid from a fixed reference point to a rotating reference point.

[0009] Yet another object of the invention is to provide a pitch change mechanism which can be used regardless of the operation of the turbomachine, which is furthermore capable of providing the functions of protecting and feathering the blades of the propeller / fan of the turbomachine, preferably without being affected by possible failures of the rotating electrical transfer.

[0010] Another aim of the invention is to propose a pitch change mechanism which can be implemented both in a turboprop or open rotor type turbomachine comprising a propeller and a turbojet comprising a fan.

[0011] To this end, the invention proposes, according to a first aspect, a mechanism for changing the pitch of a turbomachine propeller according to claim 1. Embodiments are defined in the dependent claims. PRESENTATION DES FIGURES

[0012] Other characteristics and advantages of the present invention will appear on reading the following description of a preferred embodiment. This description will be given with reference to the appended drawings in which: There figure 1 is a schematic sectional view of an example of a turbomachine comprising a variable-pitch fan or propeller and a pitch change mechanism according to one embodiment of the invention; The figure 2 is a partial and schematic sectional view of an exemplary embodiment of a mechanical reducer of the planetary type which can be used in a turbomachine comprising a pitch change mechanism according to an embodiment of the invention; The figure 3 is a schematic sectional view of an example of a turbomachine comprising a variable-pitch fan or propeller and a pitch change mechanism using a non-reversible hydraulic pump according to one embodiment of the invention; The figure 4 is a schematic sectional view of an example of a turbomachine comprising a variable-pitch fan or propeller and a pitch change mechanism using a reversible hydraulic pump according to one embodiment of the invention; The figure 5 is a schematic view of a propeller pitch change mechanism using a non-reversible hydraulic pump comprising a hydraulic feathering system according to a first embodiment; The figure 6 is a schematic view of a propeller pitch change mechanism using a non-reversible hydraulic pump comprising a hydraulic feathering system according to a second embodiment. figure 7 a schematic view of a propeller pitch change mechanism using a reversible hydraulic pump comprising a hydraulic feathering system according to the first embodiment; The figure 8 is a schematic view of a propeller pitch change mechanism using a reversible hydraulic pump comprising a hydraulic feathering system according to the second embodiment. DESCRIPTION DETAILLEE

[0013] The present invention applies to any variable-pitch turbomachine comprising a pitch-changing mechanism. In particular, the invention relates to both dual-flow turbojets comprising a fan and propeller turbomachines such as turboprops or open rotors (unducted propeller) as shown in figure 1 , the pitch of the fan or propeller blades of which can be modified according to the flight conditions. In the remainder of the application, for the sake of simplification of the description and the claims, the term “propeller” will be used to designate both a propeller as described above or a fan of a turbojet.

[0014] Conventionally, the turbomachine comprises, in addition to the propeller, a mechanical reducer 50, as illustrated by the figure 2 configured to rotate the propeller. The reducer 50 is housed in a casing of the turbomachine. The turbomachine is configured to be fixedly mounted on an aircraft by means of suitable fixing means, such as a pylon. In the following, a stator part of the turbomachine will be designated as any part fixedly mounted on a part of the turbomachine which is fixed relative to the casing which is configured to be connected to the pylon, and a rotor part of the turbomachine will be designated as any part which is movable about an axis when the turbomachine is in operation and which, by definition, is therefore mounted movable relative to the stator part. For example, the stator part comprises the casing of the turbomachine in which are housed means for driving the propeller, etc. The rotor part comprises for example the propeller as well as its drive shaft.

[0015] Finally, in the present application, upstream and downstream are defined with respect to the normal flow direction of the gas in and through the propeller. Furthermore, the axis A of the hydraulic pump is called its axis of rotation. The axial direction corresponds to the direction of the axis A and a radial direction is a direction perpendicular to this axis and passing through it. Furthermore, the circumferential (or lateral) direction corresponds to a direction perpendicular to the axis A and not passing through it. Unless otherwise specified, internal and external, respectively, are used with reference to a radial direction such that the internal part or face of an element is closer to the axis A than the external part or face of the same element.Furthermore, an element is considered "in a fixed frame of reference" when it is kept immobile in rotation relative to the axis A, while it is considered "in a rotating frame of reference" when it is likely to be driven in rotation relative to the axis A.

[0016] The 50 reducer is of the planetary type and includes: a sun gear 51, centered on an axis of rotation of the reducer and configured to be driven in rotation by a drive input shaft of the turbomachine, a crown 52, coaxial with the sun gear 51 and configured to drive in rotation the drive shaft of the propeller around the axis of rotation, and a series of satellites 53 distributed circumferentially around the axis of rotation of the reducer between the sun gear 51 and the crown 52, each satellite being meshed internally with the sun gear 51 and externally with the crown 52. The series of satellites 53 is mounted on a planet carrier 54 which is fixed relative to a stator part of the turbomachine.

[0017] Alternatively, the reducer 50 may be epicyclic, in which case the crown 52 is fixedly mounted on a stator part of the turbomachine and the drive shaft is rotated by the planet carrier 54.

[0018] In one embodiment illustrated in the figure 3 , the pitch change mechanism comprises an electrohydraulic actuator 11 (EHA, English acronym for “Electro Hydraulic Actuator”), configured to actuate a cylinder 15 which is mechanically connected to the propeller 13 in order to modify the pitch thereof, a hydraulic pump 20 configured to pressurize a fluid (typically oil) and an electric machine 29.

[0019] The electric machine 29 is fixedly mounted on the stator part of the turbomachine and comprises an actuating shaft 21 which can rotate about an axis of rotation A.

[0020] The cylinder 15 comprises a double-acting cylinder comprising a first chamber 151 and a second chamber 152 supplied successively by the hydraulic pump 20. The actuation of the hydraulic pump 20 by the electric machine 29 therefore has the effect of filling (respectively emptying) the first chamber 151 and emptying (respectively filling) the second chamber 152. The cylinder 15 is also integral in rotation with the propeller 13 and connected to the latter so that the actuation of the cylinder 15 (by successively filling and emptying the first and second chambers) has the effect of modifying the pitch of the propeller 13.

[0021] The hydraulic pump 20 may typically be a fixed displacement axial cylinder pump adapted to supply the cylinder 15 with pressurized hydraulic fluid when actuated by the electric machine 29 via the actuating shaft.

[0022] The pump may comprise a body 22 driven in rotation by the propeller 13, a barrel 23 housing a set of pistons 24 distributed circumferentially around the axis of rotation A, each piston 24 comprising a sliding pad, and a plate 26 inclined relative to the axis of rotation A, each sliding pad 25 bearing on the plate 26. In order to allow the operation of this type of pump, one of the inclined plate and the barrel 23 may be fixedly connected to the stator part of the turbomachine in order to prevent its rotation around the axis of rotation A and the other of the inclined plate 26 and the barrel 23 may be integral in rotation with the actuating shaft 21.

[0023] When the hydraulic pump used is not a reversible pump, the hydraulic actuator 11 may further comprise a hydraulic flow reversing valve 14, positioned in the hydraulic circuit in order to select the chamber of the cylinder 15 to be supplied with pressurized hydraulic fluid. The hydraulic flow reversing valve 14 is in particular configured to selectively connect one or the other of the chambers of the cylinder 15 to a pressurized fluid outlet 223 of the hydraulic pump and to a low-pressure fluid return 224, depending on the actuation requirements of the cylinder 15 to obtain the desired pitch setting for the propeller.

[0024] The hydraulic flow reversing valve 14 is controlled by a controller of the pitch change mechanism in order to put the pressurized fluid outlet 223 into fluid communication with the first or second chamber 152 of the cylinder 15, depending on the direction in which the propeller pitch is to be changed. When the propeller pitch is to be changed, the controller controls the electrical machine in order to rotate the actuating shaft 21 and to rotate the hydraulic pump 20.

[0025] This pressurized hydraulic fluid is then brought from the hydraulic pump 20 to the hydraulic flow reversing valve 14, which depending on its position (defined by the controller and the propeller timing control) will send this pressurized hydraulic fluid to one or other of the chambers of the cylinder 15. The modification of the pitch caused by the rotational drive of the actuating shaft 21 can then be measured in order to determine a torque command for the electric machine 29 making it possible to achieve the desired pitch.

[0026] In an alternative embodiment illustrated in the figure 4 , the hydraulic pump 20 may be a reversible hydraulic pump whose operation is controlled by the direction of rotation of the actuating shaft 21. Such a reversible pump may for example be obtained from a pumping assembly 2 comprising two hydraulic pumps 20a, 20b with axial pistons adapted to pressurize a hydraulic fluid sharing the same body 22 driven in rotation by the propeller 13. Each of the pumps comprising a barrel 23a, 23b housed in a cavity 221a, 221b filled in whole or in part with hydraulic fluid, the barrel 23a, 23b being fixedly connected to the stator part of the turbomachine in order to prevent its rotation around the actuating shaft 21.Each of the pumps further comprising a set of cylinders formed in the barrel 23a, 23b, each cylinder housing a piston 24 movable in translation in the cylinder and comprising an inlet orifice 242 configured to receive hydraulic fluid from the cavity 221a, 221b, and a discharge orifice 232 configured to send hydraulic fluid to a cylinder 15 for actuating the propeller, as well as a plate 26a, 26b inclined relative to the axis of rotation A and integral in rotation with the actuating shaft 21, each piston 24 bearing on a surface of the plate 26a, 26b.The plate of a first of the pumps 20a may comprise an intake lunule 261a extending circumferentially relative to the axis of rotation A and configured to allow circulation of the hydraulic fluid from the cavity 221a to the cylinders of the first of the pumps 20a when the plate 26a, 26b of said pump 20a is driven in a first direction of rotation. The plate of the second of the pumps 20b may comprise an intake lunule 261b extending circumferentially relative to the axis of rotation A configured to allow circulation of the hydraulic fluid from the cavity 221b to the cylinders of the second of the pumps 20b when the plate 26b of said pump 20b is driven in a second direction of rotation opposite to the first direction of rotation.

[0027] The electrohydraulic actuator 11 further comprises a hydraulic fluid reservoir 16 integral in rotation with the propeller 13. The reservoir has the function of guaranteeing a minimum pressure at the pump supply level through a non-return valve and also has the function of avoiding any risk of overpressure at the discharge level through a pressure relief valve in the event of overheating.

[0028] Conventionally, the pitch change mechanism may further comprise a feathering system operable in the absence of hydraulic fluid pressure. In one embodiment, the feathering system comprises counterweights of the flyweight type.

[0029] In addition to or instead of the counterweights, the pitch change mechanism comprises a hydraulic fluid reservoir 17, or high-pressure accumulator, configured to store a hydraulic fluid under pressure, and a so-called safety valve 18 controlled between a first position configured to put the first chamber 151 of the cylinder 15 into fluid communication with the hydraulic pump 20 and a second position configured to put the first chamber 151 of the cylinder 15 into fluid communication with the high-pressure accumulator 17 (see figure 5 for the case of a non-reversible pump or figure 7 for the case of a reversible pump). The high pressure accumulator 17 can be supplied with pressurized fluid directly by the hydraulic pump via a dedicated circuit (not shown in the figures).

[0030] The safety valve 18 thus makes it possible, when it is in its second position, to discharge pressurized hydraulic fluid contained in the high-pressure accumulator 17 into the first chamber 151 of the cylinder 15 and thus to feather the propeller 13. The pressure in the high-pressure accumulator 17 is chosen so as to quickly fill the first chamber 151 of the cylinder 15 in order to allow the propeller to feather.

[0031] The pitch change mechanism may include an additional hydraulic fluid reservoir 16, or low pressure accumulator, adapted to store pressurized hydraulic fluid and configured to maintain a constant volume of hydraulic fluid in the hydraulic circuit of the pitch change mechanism. The pressure of the hydraulic fluid in the low pressure accumulator 16 is lower than the pressure of the hydraulic fluid in the high pressure accumulator 17.

[0032] The safety valve 18 is controlled by the pressure of the hydraulic fluid in the hydraulic circuit of the pitch change mechanism. For this purpose, the safety valve 18 may be mounted on one side on a spring (or equivalent) having a predetermined stiffness and be connected, on the other side, to a point in the hydraulic circuit, for example at the low-pressure accumulator 16. In this way, the safety valve 18 moves from the first position to the second position when the pressure in the hydraulic circuit at the low-pressure accumulator 16 is below a predetermined threshold (which is defined by the stiffness of the spring). This control thus makes it possible to feather the propeller as soon as a hydraulic fluid leak occurs in the hydraulic circuit of the pitch change mechanism.In fact, in the event of a hydraulic fluid leak, the pressure in the hydraulic circuit gradually decreases until it reaches the predetermined threshold: the pressure is then no longer sufficient to counter the force applied by the spring on the safety valve 18, which therefore automatically moves to its second position.

[0033] The low-pressure accumulator 16 and the high-pressure accumulator 17 can be mounted in a rotating reference frame of the turbomachine, and can in particular be driven in rotation by the propeller 10. Such a configuration thus makes it possible to avoid the need to transfer the oil from an element in the fixed reference frame (stator) to the cylinder 15 which is in the rotating reference frame (driven in rotation by the propeller).

[0034] The pitch change mechanism further comprises means configured to allow discharge of the second chamber 152 into the low pressure accumulator 16 when the safety valve 18 comes into the second position, i.e. in the event of feathering.

[0035] For this purpose, in a first embodiment (see figure 5 for the case of a non-reversible pump or figure 7 for the case of a reversible pump), the pitch change mechanism may comprise a first pressure relief valve 154 configured to put the first chamber 151 of the cylinder 15 into fluid communication with the low pressure accumulator 16 when the pressure of the second chamber 152 of the cylinder 15 is greater than a predetermined threshold.

[0036] In a second embodiment illustrated by the figure 6 for the case of a non-reversible pump or by the figure 8 for the case of a reversible pump, which can be combined with the first, the pitch change mechanism further comprises an additional valve 19 called a discharge valve movable between a first position, in which the discharge valve 19 places the second chamber 152 of the cylinder 15 in fluid communication with the hydraulic pump 20, and a second position, in which the discharge valve 19 places the second chamber 152 of the cylinder 15 in fluid communication with the low pressure accumulator 16. The first position of the discharge valve 19 therefore corresponds to a normal operating position, since it allows the return of the hydraulic fluid to the hydraulic pump.

[0037] The discharge valve 19 is also controlled by the pressure in the hydraulic circuit, for example taken at the low pressure accumulator 16. In this way, the safety valve 18 and the discharge valve 19 both automatically move from the first position to the second position as soon as the pressure in the hydraulic circuit falls below the predetermined threshold.

[0038] The mechanism may further comprise a second pressure relief valve 155 configured to place the second chamber 152 of the cylinder 15 in fluid communication with the low-pressure accumulator 16 when the pressure in the second chamber 152 of the cylinder 15 is greater than a predetermined overpressure threshold. The second valve thus allows the discharge of the second chamber 152 of the cylinder 15 in the event of overpressure.

[0039] The operation of the hydraulic feathering system is carried out as follows, in the case of a pitch change mechanism comprising both the relief valve 19 and the first pressure relief valve 154. This is not, however, limiting, the pitch change mechanism may comprise only the first relief valve 154.

[0040] In normal operation (i.e. without leakage), the safety valve 18 and the relief valve 19 are placed in their first position, thus allowing the selective supply of the first chamber 151 or the second chamber 152 of the cylinder 15 by the flow reversing valve 14, or directly by the hydraulic pump when a reversible pump is used.

[0041] In the event of a leak, the pressure in the hydraulic circuit of the pitch change mechanism has the effect of reducing the pressure at the low-pressure accumulator 16. The inlet pressure of the safety valve 18 and the relief valve 19 is then no longer sufficient to resist the force applied by their spring, which has the effect of moving the safety valve 18 and the relief valve 19 from their first position to their second position. In this configuration, the first chamber 151 of the cylinder 15 is then placed in fluid communication with the high-pressure accumulator 17. The first chamber 151 of the cylinder 15 therefore quickly fills with pressurized hydraulic fluid discharged by the high-pressure accumulator 17. Simultaneously, the second chamber 152 of the cylinder 15 is placed in fluid communication with the low-pressure accumulator 16.The filling of the first chamber 151 of the cylinder 15 having the effect of increasing the pressure in the second chamber 152 of the cylinder 15, the latter is therefore gradually discharged into the low pressure accumulator 16 via the discharge valve 19.

[0042] Filling the first chamber 151 of the cylinder also has the effect of moving the piston of the cylinder 15 and therefore of modifying the timing of the propeller.

[0043] It will be noted that, when the pitch change mechanism only comprises the first pressure relief valve 154, the latter becomes open as soon as the second chamber 152 of the cylinder 15 discharges into the low pressure accumulator 16.

[0044] When the hydraulic pump used in the pitch change mechanism is not reversible, the pitch change mechanism may further comprise a flow reversing valve 14 configured to selectively place the hydraulic pump 20 in fluid communication with the first chamber 151 or the second chamber 152 of the cylinder 15, so as to allow the modification of the pitch of the propeller (see for example on the figure 8 ).

[0045] However, when a reversible hydraulic pump is used, it is not necessary to use such a flow reversing valve, as each of the cylinder chambers can be connected to one of the hydraulic pump outlets.

[0046] This configuration of the pitch change mechanism thus makes it possible to dispense with the use of a rotating oil transfer (OTB), thereby eliminating the risks of leakage and the associated oil recovery pumps as well as the associated oversizing of the oil reservoir. The circuit is also independent of the lubrication unit. In particular, the pressure delivered by the hydraulic pump 20 can reach significant levels (of the order of 300 bars), which facilitates the sizing of the cylinder 15.

[0047] It should be noted here that the feathering system only has passive actuation means, the safety valve 18 and the relief valve 19 being controlled solely by the pressure in the hydraulic circuit of the pitch change mechanism. No controller or electrical system is therefore necessary, apart from the electrical means necessary to control the flow reversing valve and the electric motor 29.

Claims

1. A mechanism for changing the pitch of a turbine engine propeller (10), said turbine engine comprising a stator portion and a rotor portion, said pitch change mechanism comprising an electrohydraulic actuator (11) comprising: - a jack for actuating (15) the propeller, comprising a first chamber (151) and a second chamber (152); - a hydraulic pump (20) adapted to selectively supply the first chamber (151) or the second chamber (152) of the jack (15) with pressurized hydraulic fluid; - a hydraulic fluid tank (17) configured to store a pressurized hydraulic fluid; - a valve (18) controlled between a first position, in which the valve (18) puts the first chamber (151) of the jack (15) in fluid communication with the hydraulic pump (20), and a second position in which the valve (18) puts the first chamber (151) of the jack (15) in fluid communication with the hydraulic fluid tank (17), the pitch change mechanism being characterized in that it further comprises an additional hydraulic fluid tank (16), a pressure of the hydraulic fluid tank (17) being greater than a pressure of the additional hydraulic fluid tank (16), and in that the valve (18) is controlled by the pressure from said additional hydraulic fluid tank (16) and moves from the first position to the second position when the pressure of the additional hydraulic fluid tank (16) is below a predetermined threshold.

2. The pitch change mechanism according to claim 1, wherein the additional hydraulic fluid tank (16) is configured to be mounted in a rotating reference frame of the turbine engine.

3. The pitch change mechanism according to any of claims 1 and 2, further comprising a pressure relief valve (155) and / or an additional valve (19) configured to put the second chamber (152) of the jack (15) in fluid communication with the additional hydraulic tank (16) when the additional valve (19) is in the second position.

4. The pitch change mechanism according to claim 3, wherein the pressure relief valve (155) and / or the additional valve (19) are controlled by the pressure of the additional fluid tank (16).

5. The pitch change mechanism according to any of claims 1 to 4, further comprising an additional pressure relief valve (154) configured to put the first chamber (151) of the jack in fluid communication with the additional hydraulic fluid tank (16) when the pressure of the first chamber (151) of the jack is above a predetermined threshold.

6. The pitch change mechanism according to any of claims 1 to 5, wherein the hydraulic fluid tank (17) is configured to be mounted in a rotating reference frame of the turbine engine.

7. The pitch change mechanism according to any of claims 1 to 6, wherein the body (22) of the pump is configured to be in a rotating reference frame of the turbine engine and one among the inclined plate and the barrel (23) of the pump is configured to be in a fixed reference frame of the turbine engine.

8. The pitch change mechanism according to claim 7, wherein in the absence of rotation between the fixed reference frame and the rotating reference frame, the flow rate of the pump is null.

9. The pitch change mechanism according to any of claims 1 to 8, further comprising a flow rate reversal valve configured to selectively put the hydraulic pump (20) in fluid communication with the first chamber (151) or the second chamber (152) of the jack (15).

10. The pitch change mechanism according to any of claims 1 to 9, wherein the hydraulic pump (20) is reversible.

11. A turbine engine comprising a propeller (13) and a pitch change mechanism according to any of claims 1 to 10 configured to actuate a cylinder (15) which is mechanically connected to the propeller (13).

12. An aircraft comprising at least one turbine engine according to claim 11 connected on the aircraft via a pylon.