Self-balancing device for turbomachine rotor

Abstract

A self-balancing device (34) for a turbomachine rotor comprises a balancing weight (40); an electromechanical actuator (42) configured to move the balancing weight (40) along a predetermined path when the actuator is supplied with electrical current; a suspended weight (44); and power supply means (46) configured to supply the actuator (42) with electrical current generated by converting mechanical energy from the vibrations of the suspended weight (44). Such a device allows the rotor to be balanced autonomously, without requiring an external electrical power supply for controlling or powering the device. (See Figure 3 for abbreviations.)

Description

Title of the invention: Self-balancing device for a turbine rotor Technical field

[0001] The present invention relates to the field of turbomachines, in particular of the type intended for the propulsion of aircraft, and relates more particularly to a self-balancing device intended for the rotational balancing of turbomachine rotors, and more particularly intended to correct an unbalance affecting such a rotor. State of the prior art

[0002] In turbomachines, rotor balancing is necessary in order to limit the loads and vibrations transmitted to the structures, and to reduce various functional clearances such as clearances at the blade tips.

[0003] Measures are taken for this purpose during the manufacture of the rotors and during their assembly.

[0004] However, a residual unbalance which is difficult to estimate precisely generally remains at the end of the assembly of the turbomachine.

[0005] Furthermore, it is common for an imbalance to occur after the turbomachine has been put into service, due to wear of the parts or following specific events such as the ingestion of foreign bodies by the turbomachine.

[0006] The applicant's patents FR3064064B1 and FR3004418B1 propose systems capable of balancing a turbomachine rotor after the manufacture and assembly of the elements of the latter, including during operation of the turbomachine. Such systems are based on computers designed to estimate the intensity and location of an unbalance from information provided by sensors provided for this purpose, and designed to deduce therefrom an actuator command making it possible to move balancing weights into an appropriate configuration.

[0007] Such systems, however, require complex and expensive means to provide the electrical power supply and control of the actuators, requiring the electric current to be passed between rotor parts and stator parts. Statement of the invention

[0008] The invention aims to remedy these problems at least in part.

[0009] For this purpose, it proposes a self-balancing device for a turbomachine rotor, comprising: • a balancing weight; • an electromechanical actuator configured to move the weight balancing along a determined trajectory, when the electromechanical actuator is supplied with electric current; • a suspended weight; and • power supply means configured to supply the electromechanical actuator with electric current generated by converting mechanical energy from vibrations of the suspended weight.

[0010] The invention thus proposes a rotor balancing device capable of operating autonomously, without requiring an external supply of electrical energy for its control or power supply.

[0011] In preferred embodiments of the invention, the power supply means comprise a piezoelectric sensor having a sensitive membrane to which the suspended weight is fixed so that vibrations of the suspended weight, transmitted to the sensitive membrane, cause the generation, by the piezoelectric sensor, of a power supply current for the electromechanical actuator.

[0012] In preferred embodiments of the invention, the power supply means comprise a rectifier bridge electrically interposed between output terminals of the piezoelectric sensor and terminals of the electromechanical actuator so as to rectify the power supply current of the electromechanical actuator generated by the piezoelectric sensor.

[0013] In preferred embodiments of the invention, the electromechanical actuator is configured to move the balance weight by screw-nut effect whereby said predetermined trajectory is a linear trajectory.

[0014] In preferred embodiments of the invention, the device comprises an end-of-travel reversing device configured to react to the arrival of the balancing weight at the end of its travel by reversing a direction of movement of the balancing weight, along said predetermined trajectory, by the actuator.

[0015] The invention also relates to a turbomachine, comprising at least one rotor mobile in rotation around an axis and on which is fixed at least one self-balancing device of the type described above.

[0016] In preferred embodiments of the invention, the turbomachine comprises, for each self-balancing device, a corresponding compensatory weight, of the same mass as the self-balancing device and arranged so that the self-balancing device and the compensatory weight have respective centers of inertia symmetrical to each other with respect to the axis when the self-balancing device is in a neutral configuration.

[0017] The invention also relates to a method for self-balancing a turbomachine rotor, comprising: • A) the fixing of at least one self-balancing device of the type described above- above on the rotor; • B) supplying the electromechanical actuator with electric current generated by converting mechanical energy from vibrations of the suspended weight induced by an unbalance, whereby the electromechanical actuator moves the balancing weight along said determined trajectory.

[0018] In preferred embodiments of the invention, the method comprises detecting an arrival of the balancing weight at the end of its travel, and reversing a direction of movement of the balancing weight along said trajectory by the electromechanical actuator.

[0019] In preferred embodiments of the invention, step A comprises fixing, on the rotor, at least one compensating weight of the same mass as the self-balancing device and arranged so that the self-balancing device and the compensating weight have respective centers of inertia symmetrical to each other with respect to an axis of the rotor when the self-balancing device is in a neutral configuration. Brief description of the drawings

[0020] 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:

[0021] [Fig-1] is a schematic axial sectional view of a turbomachine intended for the aircraft propulsion;

[0022] [Fig.2] is a schematic front view of a rotor element, such as a disc bladed, of the turbomachine, equipped with self-balancing devices according to a preferred embodiment of the invention;

[0023] [Fig.3] is a schematic front view of a self-balancing device of the rotor of the [Fig.2] ;

[0024] [Fig.4] is an electrical diagram of the self-balancing device of [Fig.3].

[0025] Throughout these figures, identical references may designate identical or similar elements. Detailed disclosure of preferred embodiments

[0026] [Fig. 1] illustrates a turbomachine 10, for example a twin-spool, dual-flow turbojet for aircraft, generally comprising a fan 12 intended for the suction of an air flow F1 dividing downstream of the fan into a primary flow F2 circulating in a primary flow channel, hereinafter referred to as the primary flow path PV, and a secondary flow F3 circulating in a secondary flow channel, hereinafter referred to as the secondary flow path SV, arranged around the flow path PV primary.

[0027] 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.

[0028] The respective rotors of the high-pressure compressor and the high-pressure turbine are connected by a shaft called a "high-pressure shaft", while the respective rotors of the low-pressure compressor and the low-pressure turbine are connected by a shaft called a "low-pressure shaft", in a well-known manner. These rotors are rotatably mounted around an axis 28 of the turbomachine.

[0029] Throughout this description, the axial direction X is the direction of the axis 28. The radial direction R is at all points a direction orthogonal to the axis 28 and passing through the latter, and the orthoradial or circumferential direction C is at all points a direction 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 of the flow of the gases in the primary PV and secondary SV veins of the turbomachine, in the axial direction X.

[0030] [Fig. 2] illustrates an element belonging to one of the rotors of the turbomachine, in this case a bladed disc 30. This comprises an annular row of blades 30A fixed to - or formed in one piece with - a hub 30B, in a manner known per se. The invention is of course applicable to any type of rotor.

[0031] The bladed disc 30 further comprises, for example on one of the faces 32 of the hub 30B, one or more self-balancing devices 34, for example five in number.

[0032] Such a device 34, visible in more detail in [Fig. 3], comprises a balancing weight 40, an electromechanical actuator 42, a suspended weight 44, and supply means 46. The device 34 further comprises a chassis taking for example essentially the form of a fixing plate 48 by which the device is fixed on the rotor, for example by bolting.

[0033] The power supply means 46 are configured to supply the actuator 42 - more precisely an electric motor of the actuator - with electric current generated by converting vibratory mechanical energy of the suspended weight 44, that is to say mechanical energy corresponding to possible vibrations of the suspended weight 44 such as vibrations resulting from an unbalance of the rotor.

[0034] For this purpose, the supply means 46 advantageously comprise a piezoelectric sensor 50 having a sensitive membrane 52 to which the suspended weight 44, whereby any vibrations of the suspended weight 44 result in vibrations of the sensitive membrane 52 and thus cause the generation, by the piezoelectric sensor 50, of an electric current used to power the actuator 42.

[0035] As appears more clearly in the electrical diagram of [Fig. 4], the power supply means 46 advantageously comprise a full-wave rectifier bridge 54 having two input terminals 54A, 54B to which two terminals 50A, 50B of the piezoelectric sensor 50 are respectively connected, and two output terminals 55A, 55B respectively connected to two terminals 42A, 42B of the actuator 42, in this case by means of an end-of-travel reversing device 65, which will be described below.

[0036] The actuator 42 is configured to move the balancing weight 40 along a determined trajectory, when the actuator is supplied with electrical current.

[0037] The balancing weight 40 has a mass determined to allow the generator 52 to generate an electric current sufficient to cause a displacement of the balancing weight 40 by the actuator 42 as soon as an unbalance considered to be significant occurs.

[0038] In the preferred example illustrated, the actuator 42 is configured to move the balancing weight 40 by screw-nut effect.

[0039] For this purpose, with reference to [Fig. 3], the actuator is a linear actuator, comprising an electric motor 56 whose rotor is integral in rotation with an output shaft 58 having a thread engaged with the tapping of a through-orifice 60 of the balancing weight 40. In addition, an auxiliary shaft 62 integral with the frame of the device 34 passes through an off-center orifice 64 of the balancing weight 40 so as to prevent the latter from rotating with the output shaft 58 and to force the balancing weight 40 to move along the shafts 58, 62 when the output shaft 58 is driven in rotation by the motor 56.

[0040] The device 34 further advantageously comprises an end-of-travel reversal device 65 configured to react to the arrival of the balancing weight 40 at the end of its travel by reversing a direction of movement of the balancing weight 40, along its trajectory, by the actuator 42 ([Fig.3]).

[0041] For this purpose, the end-of-travel reversing device comprises end-of-travel reversers 66A, 66B which are preferably two-way contactors, respectively arranged at two opposite ends of the path of the balancing weight 40 so as to be actuated by the latter when it reaches the end of its travel, and configured so that their actuation by the balancing weight 40 causes the inversion of the state of a corresponding set 68A, 68B of switches ([Fig.4]). It should be understood by this that the actuation of a first 66A of the limit switches causes the inversion of the state of switches IntAl to IntA4 constituting a first 68A of the switch sets. Similarly, the actuation of the other limit switch 66B causes the inversion of the state of switches IntBl to IntB4 constituting a second 68B of the switch sets.

[0042] In addition, the switches IntAl to IntA4 of the first set 68A are associated two by two with the switches IntB 1 to IntB4 of the second set 68B so as to form as many “two-way” circuits Circl to Circ4.

[0043] In particular, the switches IntA1 and IntA4 of the first set 68A have respective input terminals connected to a first 55A of the output terminals of the full-wave rectifier bridge 54, while the switches IntA2 and IntA3 of the first set 68A have respective input terminals connected to the second output terminal 55B of the full-wave rectifier bridge 54. In addition, the switches IntB1 and IntB2 of the second set 68B have respective output terminals connected to a first 42A of the terminals of the actuator 42, while the switches IntB3 and IntB4 of the second set 68B have respective output terminals connected to the second terminal 42B of the actuator 42.

[0044] The initial state of the switches IntA1 to IntA4 and IntB1 to IntB4 is such that, when any one of the end-of-travel inverters 66A, 66B is actuated by the balancing weight 40 reaching the end of its travel and causes the inversion of the state of the switches of the corresponding assembly 68A or 68B, an inversion of the polarity of the power supply to the actuator 42 results, with the consequence of an inversion of the direction of movement of the balancing weight 40.

[0045] Furthermore, with reference to [Fig. 2], the bladed disc 30 comprises compensatory weights 70 intended to maintain overall balancing of the rotor despite the additional mass induced by the presence of the self-balancing devices 34. For this purpose, the compensatory weights 70 are provided in a number equal to the number of self-balancing devices 34, and are arranged so that the centers of inertia 70A of the compensatory weights 70 are respectively arranged symmetrically to the centers of inertia 34A of the self-balancing devices 34 relative to the axis 28, when the self-balancing devices 34 are in a neutral configuration. The term “neutral configuration” should be understood to mean a configuration in which the balancing weights 40 are located halfway between the opposite ends of their respective trajectories.

[0046] Thus, in operation, any unbalance tends, depending on its orientation and from a certain intensity, to preferentially excite one of the self-balancing devices 34. This results in vibrations of the suspended weight 44 and therefore of the sensitive membrane 52 of the piezoelectric sensor 50, inducing the supply of the actuator 42 and thus causing the latter to operate. This results in a movement of the balancing weight 40 in a given direction.

[0047] If this direction leads to reducing the unbalance, the device 34 gradually ceases to be excited and the movement of the balancing weight 40 ends.

[0048] Otherwise, the balancing weight 40 continues to move until the imbalance is minimized.

[0049] In the case where the movement of the balancing weight 40 aggravates the unbalance, the weight continues its movement until it actuates the corresponding limit switch 66A or 66B. This results in a reversal of the polarity of the electric current supplying the actuator 42 and therefore a reversal of the direction of movement of the balancing weight 40. The latter then continues its movement in the other direction, until the unbalance is finally minimized.

[0050] In all cases, it thus appears that the self-balancing device(s) 34 lead to a reduction, or even elimination, of the unbalance, and this in a completely autonomous manner, without the supply of electrical energy from outside.

[0051] A method for self-balancing a turbomachine rotor according to the invention therefore generally comprises: • A) fixing at least one self-balancing device 34 of the type described above on the rotor; • B) supplying the electromechanical actuator 42 with electric current generated by converting mechanical energy from vibrations of the suspended weight 44, induced by an unbalance, whereby the electromechanical actuator 42 moves the balancing weight 40 along its path.

[0052] In the example described above, the method further comprises: • C) the detection of a possible arrival of the balancing weight 40 at the end of its travel by means of the corresponding end-of-travel inverter 66A or 66B, causing the inversion of the polarity of the electric current supplying the electromechanical actuator 42 and therefore the inversion of the direction of movement of the balancing weight 40 along its trajectory by the actuator 42.

[0053] In addition, step A further advantageously comprises the fixing, on the rotor, of at least one compensatory weight 70 - one for each self-balancing device 34 - of the same mass as the self-balancing device 34 and arranged so that the self-balancing device 34 and the compensatory weight 70 have respective centers of inertia 34A, 70A symmetrical to each other with respect to the axis 28 when the self-balancing device 34 is in a neutral configuration.

Claims

Claims

1. Self-balancing device (34) for a turbomachine rotor, comprising: • a balancing weight (40); • an electromechanical actuator (42) configured to move the balancing weight (40) along a determined trajectory, when the electromechanical actuator is supplied with electric current; • a suspended weight (44); and • supply means (46) configured to supply the electromechanical actuator (42) with electric current generated by converting mechanical energy from vibrations of the suspended weight (44).

2. Self-balancing device according to claim 1, in which the supply means (46) comprise a piezoelectric sensor (50) having a sensitive membrane (52) to which the suspended weight (44) is fixed so that vibrations of the suspended weight, transmitted to the sensitive membrane (52), cause the generation, by the piezoelectric sensor (50), of a supply current for the electromechanical actuator (42).

3. A self-balancing device according to claim 2, wherein the power supply means (46) comprises a rectifier bridge (54) electrically interposed between output terminals (50A, 50B) of the piezoelectric sensor (50) and terminals (42A, 42B) of the electromechanical actuator (42) so as to rectify the supply current of the electromechanical actuator (42) generated by the piezoelectric sensor (50).

4. Self-balancing device according to any one of claims 1 to 3, wherein the electromechanical actuator (42) is configured to move the balancing weight (40) by screw-nut effect whereby said predetermined trajectory is a linear trajectory.

5. Self-balancing device according to any one of claims 1 to 4, comprising an end-of-travel reversing device (65) configured to react to the arrival of the balancing weight (40) at the end of its travel by reversing a direction of movement of the weight. balancing (40), along said predetermined trajectory, by the actuator (42).

6. Turbomachine, comprising at least one rotor (30) movable in rotation around an axis (28) and on which is fixed at least one self-balancing device (34) according to any one of claims 1 to 5.

7. Turbomachine according to claim 6, comprising, for each self-balancing device (34), a corresponding compensatory weight (70), of the same mass as the self-balancing device (34) and arranged so that the self-balancing device (34) and the compensatory weight (70) have respective centers of inertia (34A, 70A) symmetrical to each other with respect to the axis (28) when the self-balancing device (34) is in a neutral configuration.

8. A method for self-balancing a turbomachine rotor (30), comprising: • A) fixing at least one self-balancing device (34) according to any one of claims 1 to 5 on the rotor (30); • B) supplying the electromechanical actuator (42) with electric current generated by converting mechanical energy from vibrations of the suspended weight (44) induced by an unbalance, whereby the electromechanical actuator (42) moves the balancing weight (40) along said determined trajectory.

9. Method according to claim 8, in which the self-balancing device (34) is a device according to claim 5, the method comprising: • C) detecting an arrival of the balancing weight (40) at the end of its travel, and reversing a direction of movement of the balancing weight (40) along said trajectory by the electromechanical actuator (42).

10. A method according to claim 8 or 9, wherein step A comprises fixing, on the rotor (30), at least one compensating weight (70) of the same mass as the self-balancing device (34) and arranged so that the self-balancing device (34) and the weight com- pensatory (70) have respective centers of inertia (34A, 70A) symmetrical to each other with respect to an axis (28) of the rotor when the self-balancing device (34) is in a neutral configuration.

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