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 turbine rotor technical field

[0001] The present invention relates to the field of turbomachinery, in particular of the type intended for aircraft propulsion, and more particularly concerns a self-balancing device intended for the rotational balancing of turbomachine rotors, and more particularly intended for correcting an imbalance affecting such a rotor. Prior art

[0002] In turbomachinery, rotor balancing is necessary to limit the loads and vibrations transmitted to the structures, and to reduce various functional clearances such as blade tip clearances.

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

[0004] However, a residual imbalance, difficult to estimate precisely, generally remains after the assembly of the turbomachine.

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

[0006] Patents FR3064064B1 and FR3004418B1 of the applicant describe systems capable of balancing a turbomachine rotor after the manufacturing and assembly of its components, including during turbomachine operation. Such systems rely on computers designed to estimate the magnitude and location of an imbalance from information provided by sensors intended for this purpose, and designed to derive from this information a command for actuators that move balancing weights into a suitable configuration.

[0007] Such systems, however, require complex and costly means to ensure the power supply and control of the actuators, requiring the passage of electric current between parts of the rotor and parts of the stator. Description of the invention

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

[0009] To this end, 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 powered by electric current; • a suspended weight; and • power supply means configured to supply the electromechanical actuator with electrical 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 external electrical power for its control or 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 attached such that vibrations of the suspended weight, transmitted to the sensitive membrane, cause the piezoelectric sensor to generate a power supply current to 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 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 balancing weight by screw-nut effect, whereby said predetermined trajectory is a linear trajectory.

[0014] In preferred embodiments of the invention, the device includes a limit switch device configured to react to the arrival of the balancing weight at the end of its stroke by reversing one direction of the 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 that rotates about 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 includes, for each self-balancing device, a corresponding 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 that are 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 attachment of at least one self-balancing device of the type described below top on the rotor; • B) the supply of the electromechanical actuator with electrical current generated by converting mechanical energy from vibrations of the suspended weight induced by an imbalance, whereby the electromechanical actuator moves the balancing weight along said determined trajectory.

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

[0019] In preferred embodiments of the invention, step A includes 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 features thereof will become apparent from the following description, given by way of non-limiting example and with reference to the accompanying drawings in which:

[0021] [Fig-1] is a schematic axial cross-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 disk aubagé, 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 analogous elements. Detailed presentation of preferred embodiments

[0026] Figure 1 illustrates a turbomachine 10, for example a twin-spool turbofan engine for aircraft, generally comprising a fan 12 for drawing in an airflow Fl, which divides downstream of the fan into a primary flow F2 circulating in a primary flow channel, hereinafter referred to as the primary stream PV, and a secondary flow F3 circulating in a secondary flow channel, hereinafter referred to as the secondary stream SV, arranged around the stream primary PV.

[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 together define the primary flow PV.

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

[0029] Throughout this description, the axial direction X is the direction of axis 28. The radial direction R is at every point a direction orthogonal to and passing through axis 28, and the orthoradial or circumferential direction C is at every point a direction orthogonal to the radial direction R and to axis 28. A transverse plane is a plane orthogonal to axis 28. The terms "internal" and "external" refer respectively to a relative proximity and a relative distance of an element from axis 28. Finally, the "upstream" and "downstream" directions are defined with reference to the general direction of gas flow in the primary PV and secondary SV sections of the turbomachine, along the axial direction X.

[0030] Figure 2 illustrates an element belonging to one of the rotors of the turbomachine, namely a bladed disc 30. This disc comprises an annular row of blades 30A fixed to—or formed as a single unit 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], includes a balancing weight 40, an electromechanical actuator 42, a suspended weight 44, and power supply means 46. The device 34 further includes a chassis taking, for example, essentially the form of a mounting plate 48 by which the device is fixed to 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 from the suspended weight 44, i.e. mechanical energy corresponding to possible vibrations of the suspended weight 44 such as vibrations resulting from an imbalance of the rotor.

[0034] For this purpose, the power 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 piezoelectric sensor 50 to generate an electric current which is used to power the actuator 42.

[0035] As is more clearly shown 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 are respectively connected two terminals 50A, 50B of the piezoelectric sensor 50, and two output terminals 55A, 55B respectively connected to two terminals 42A, 42B of the actuator 42, in this case via a limit switch reversing device 65, which will be described below.

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

[0037] The balancing weight 40 has a determined mass to enable 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 imbalance considered significant occurs.

[0038] In the preferred example shown, 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 rotationally fixed to an output shaft 58 having a thread engaging with the tapping of a through hole 60 in the balancing weight 40. In addition, an auxiliary shaft 62 fixed to the frame of the device 34 passes through an off-center hole 64 in the balancing weight 40 so as to prevent the latter from rotating with the output shaft 58 and to constrain the balancing weight 40 to move along the axes 58, 62 when the output shaft 58 is driven in rotation by the motor 56.

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

[0041] To this end, the limit switch reversing device comprises two limit switches 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 reversal of the state of a corresponding set of switches 68A, 68B ([Fig. 4]). It should be understood that the actuation of a first 66A of the limit switches causes the state of switches IntAl to IntA4, forming the first 68A of the switch sets. Similarly, actuation of the other limit switch 66B causes the state of switches IntBl to IntB4, forming a second 68B of the switch sets.

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

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

[0044] The initial state of the switches IntAl to IntA4 and IntB 1 to IntB4 is such that, when any one of the limit switches 66A, 66B is actuated by the balancing weight 40 coming to the end of its stroke and causes the inversion of the state of the switches of the corresponding assembly 68A or 68B, an inversion of the polarity of the supply of 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 includes compensating weights 70 designed to maintain overall rotor balance despite the additional mass induced by the presence of the self-balancing devices 34. To this end, the compensating 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 compensating weights 70 are respectively arranged symmetrically to the centers of inertia 34A of the self-balancing devices 34 with respect to the axis 28, when the self-balancing devices 34 are in a neutral configuration. A "neutral configuration" is to be understood as a configuration in which the balancing weights 40 are located midway between the opposite ends of their respective trajectories.

[0046] Thus, during operation, any imbalance tends, depending on its orientation and above 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 displacement of the balancing weight 40 in a given direction.

[0047] If this direction leads to a reduction of the imbalance, the device 34 gradually ceases to be excited and the movement of the balancing weight 40 comes to an end.

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

[0049] If the movement of the balancing weight 40 increases the imbalance, 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 weight then continues its movement in the opposite direction until the imbalance is finally minimized.

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

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

[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 stroke by means of the corresponding end-of-stroke reverser 66A or 66B, causing the reversal of the polarity of the electric current supplying the electromechanical actuator 42 and therefore the reversal of the direction of movement of the balancing weight 40 along its trajectory by the actuator 42.

[0053] In addition, step A further advantageously includes the fixing, on the rotor, of at least one compensating 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 compensating 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

Demands

1. Self-balancing device (34) for turbomachine rotor, comprising: • a balancing weight (40); • an electromechanical actuator (42) configured to move the balancing weight (40) along a predetermined path, when the electromechanical actuator is supplied with electric current; • a suspended weight (44); and • power 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, wherein the power supply means (46) comprise a piezoelectric sensor (50) having a sensitive membrane (52) to which the suspended weight (44) is attached such that vibrations of the suspended weight, transmitted to the sensitive membrane (52), cause the piezoelectric sensor (50) to generate a power supply current to the electromechanical actuator (42).

3. Self-balancing device according to claim 2, wherein the power supply means (46) comprise 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. A self-balancing device according to any one of claims 1 to 4, comprising a limit switch reversing device (65) configured to react to the arrival of the balancing weight (40) at the end of its stroke by reversing one direction of the weight's movement. balancing (40), along said predetermined trajectory, by the actuator (42).

6. Turbomachine, comprising at least one rotor (30) movable in rotation about 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 compensating weight (70) of the same mass as the self-balancing device (34) and arranged so that the self-balancing device (34) and the compensating 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) attaching at least one self-balancing device (34) according to any one of claims 1 to 5 to the rotor (30); • B) supplying the electromechanical actuator (42) with electrical current generated by converting mechanical energy from vibrations of the suspended weight (44) induced by an imbalance, whereby the electromechanical actuator (42) moves the balancing weight (40) along said determined trajectory.

9. A method according to claim 8, wherein the self-balancing device (34) is a device according to claim 5, the method comprising: • C) the detection of an arrival of the balancing weight (40) at the end of the stroke, and the reversal of 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 attaching to 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 compensating weight- pensatoire (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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