FR3108048A1 - TURBOMACHINE PART BALANCING PROCESS AND DEVICE - Google Patents

Abstract

TITLE: TURBOMACHINE PART BALANCING METHOD AND DEVICE The invention relates to a device (2) for balancing a turbomachine rotating part for an aircraft comprising: a frame (6) capable of receiving the rotating part (1) movable in rotation along an axis of rotation relative to the frame, the rotating part (1) being equipped with a bead of material (5), at least one guide bearing (9, 10) in rotation of the rotating part (1), a rotating element (11) of the rotating part (1) around the axis of rotation, and at least one machining element (12) mounted on the frame movably along a radial axis perpendicular to the axis of the rotating part, the machining element (12) being configured to machine the bead of material (5) when the rotating part (1) moves towards the machining element along a line parallel to a direction of an unbalance vector (Vb) and at the location of the unbalance. Figure for the abstract: Figure 1

Description

TURBOMACHINE PART BALANCING PROCESS AND DEVICE

Field of the invention

The present invention relates to the field of turbomachines for aircraft. It relates in particular to a balancing device and a method for balancing rotating parts of a turbomachine.

Technical background

An aircraft turbomachine generally comprises one or more rotating parts or modules known by the term rotors which rotate about an axis of rotation. Despite all the care and precision taken in the design and manufacture of the rotating parts of the turbomachine, some of them contain unbalance which can penalize the operation of the turbomachine. An unbalance is a mass that is distributed unevenly around the axis of the rotating part. The latter generally rotates at speeds of the order of several thousand revolutions per minute. A rotor comprising an unbalance generates vibrations, forces on the turbomachine and thus premature wear of the parts of the turbomachine.

It is known to use balancers to achieve precise balancing of the rotors. In general, the operator installs a rotor on a balancing device which drives it in rotation, reads the result of the check on the balancing device or on another station. If there is an imbalance and this exceeds the specifications provided by the designer, the operator must make a correction such as material removal (machining, etc.) or by adding material (weights or others). The corrected rotor is checked again on the balancing device to verify that the unbalance has been corrected. These steps will be repeated until the piece is well balanced. These iterations are time consuming and therefore have a certain cost.

The objective of the present invention is to easily and automatically balance a rotating part of a turbomachine while avoiding readings and / or various manipulations of the part on a balancing device.

We achieve this in accordance with the invention with an aircraft turbomachine rotating part balancing device comprising:

• a frame capable of receiving the rotating part which is movable in rotation along an axis of rotation relative to the chassis, the rotating part being equipped with a bead of material,
• at least one rotating guide bearing for the rotating part,
• an element for rotating the rotating part around the axis of rotation,
• at least one machining element mounted on the frame movably along a radial axis perpendicular to the axis of rotation of the rotating part, the machining element being configured so as to machine the bead of material when the part is moves towards the machining element along a straight line parallel to a direction of an unbalance vector and to the location of the unbalance.

Thus, this solution achieves the above objective. In particular, the device uses the "deformation" of the rotating part along a line parallel to the unbalance vector, to machine the bead of material at the location of the unbalance. No measuring means or any control means are necessary to determine the unbalance and to balance the rotating part of the turbomachine. In addition, this avoids handling (reading information concerning the correction on another tool, correcting the unbalance, moving the part on the tool to correct, etc. until complete balancing), in particular when the rotating part of the turbomachine is relatively heavy and bulky. The bead of material is machined with each pass near the machining element until the part no longer "deforms" during rotation. If there is no defect, there is no deformation of the part, ie no unbalance correction.

In the present description, by the terms “deformed” and “deformation” we mean a displacement of the axis of the rotating part relative to an axis of rotation of the latter when the latter is set in rotation. .

The device also includes one or more of the following features, taken alone or in combination:

• the rotation of the part creates a displacement in the direction of the unbalance vector with a rotation at low speed.
• the rotation of the part creates a displacement in a direction opposite to that of the unbalance vector with a high speed rotation.
• the machining element moves in translation along the radial axis at a speed between 10 and 500 µm / s.
• the machining element includes an abrasive element such as a grinding wheel.
• the rotating element is a motor.
• the machining element is arranged outside the rotating part.
• the machining element is suitable for being arranged inside the rotating part.
• the machining element is unique.
• the machining element is stationary in rotation.

The invention also relates to a method for balancing a rotating part of an aircraft turbomachine, the method comprising the following steps:

• installation of the rotating part which is hollow and which is equipped with a bead of material on a balancing device having any of the preceding characteristics,
• rotating the rotating part along an axis of rotation at a frequency of rotation different from a frequency of the predetermined vibration mode of the balancing device and of the rotating part, and
• balancing the rotating part by machining a portion of the bead of material as the rotating part moves toward the machining element in a direction corresponding to an unbalance vector and the location of the unbalance.

The method also includes one or more of the following characteristics or steps, taken alone or in combination:

• the machining element moves in translation along the radial axis R at a speed between 10 and 500 µm / s.
• the bead of material is disposed on a non-functional surface of the rotating part and facing the machining element.
• the frequency of rotation of the rotating part depends on the position of the bead of material on the rotating part.
• the frequency of rotation is based on the first bending mode.
• the value of the predetermined vibration mode frequency is stored in a memory of an electronic control unit.
• the rotating part is arranged so that the bead of material is disposed opposite the machining element.
• the bead of material is disposed on a radially outer surface of the rotating part.
• the bead of material is disposed on a radially internal surface of the rotating part.
• the rotating part rotates at a rotational frequency lower than the predetermined vibration mode frequency if the bead of material is disposed on a radially outer surface of the rotating part.
• the rotating part rotates at a frequency of rotation higher than the frequency of the predetermined vibration mode if the bead of material is disposed on a radially internal surface of the rotating part.

Finally, the invention relates to a rotating part of a turbomachine which has undergone balancing according to the method as mentioned above.

The invention further relates to an aircraft turbomachine comprising at least one rotating part of a turbomachine balanced according to the balancing method as mentioned above. The turbomachine can be a turboprop or a turbojet.

Brief description of the figures

The invention will be better understood, and other aims, details, characteristics and advantages thereof will emerge more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given by way of illustration. purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

FIG. 1 is a schematic view in axial section of a balancing device on which is mounted a rotating part of an aircraft turbomachine according to the invention;

FIG. 2a-2c shows schematically and in radial cross section different positions of a rotating part of a turbomachine with a bead of material on a radially outer surface; in FIG. 2a, the rotating part is in a rest position, in FIG. 2b the rotating part rotates along its axis of rotation relative to a balancing element of the balancing device during its operation and FIG. 2c represents the rotating part after correction of the unbalance according to the invention;

FIG. 3a-3c shows schematically and in radial cross section different positions of a rotating part of a turbomachine with a bead of material on a radially internal surface; in FIG. 3a, the rotating part is in a rest position, in FIG. 3b the rotating part rotates along its axis of rotation relative to a balancing element of the balancing device during its operation according to the invention; and FIG. 3c represents the rotating part after correction of the unbalance according to the invention;

FIG. 4 represents a phase shift between the unbalance of the rotating part and the displacement of the rotating part in a rotating frame according to the invention.

Detailed description of the invention

FIG. 1 represents a rotating part of a turbomachine and in particular of an aircraft turbomachine. The turbomachine can be a turbojet or even a turboprop.

The rotating part 1 which is intended to equip the turbomachine is mounted on a balancing device 2 with a view to balancing it.

The turbomachine comprises one or more rotating parts or rotors such as turbomachine shafts (low pressure shaft, high pressure shaft, free turbine shaft, fan shaft), turbomachine housings, turbomachine disks, ferrules, etc. The rotating part is made from a single piece (or from one piece). Alternatively, the rotating part is formed from several elements which have been assembled together (eg a disc with at least one stage of blades which extend radially from the periphery of the disc.

Of course, the invention applies to any mechanical part capable of rotating at very high speeds such as several thousand revolutions per minute. With such speeds, the rotating part must be perfectly balanced to avoid vibrations, noise, etc. so as to guarantee optimum performance of the turbomachine.

By the terms “balancing” or “balancing” we mean in the present invention the fact of compensating for unbalances existing on turbomachine parts by adding or removing material. Preferably, in the present invention, the balancing is carried out by removing material.

Advantageously, but without limitation, the rotating part rotates around a longitudinal axis X (which may be coaxial with the axis of the turbomachine when installed in the turbomachine). As we can see in Figure 1, the rotating part 1 is preferably, but not limited to, a hollow part. This comprises a radially outer surface 3 and a radially inner surface 4 opposed along a radial axis R perpendicular to the longitudinal axis X.

The rotating part 1 comprises a bead of material 5 on a non-functional surface thereof. The dimensions of the bead will depend on the maximum correction unbalance required, and therefore on the quality of the manufacture of the rotating rotor. In other words, depending on the application of the rotating part, its dimensions, or even the manufacturer, the rotating part may have a maximum permissible unbalance. The non-functional surface may be the radially outer surface as shown in Figures 1 and 2 or on the radially inner surface as shown in Figure 3. The arrangement of the bead of material 5 on the rotating part depends for example the size of the environment where the part will be mounted in the turbomachine. In this way, if the rotating part is intended to be mounted in a very congested area of the turbomachine, the bead of material 5 will be provided inside the rotating part and thus on the radially internal surface 4. This arrangement may depend on also of the rotational capacity of a rotating element 11 described below with regard to the frequency of a first bending mode of the part to be balanced.

The bead of material 5 is also made in one piece with the rotating part. In other words, the bead of material 5 and the rotating part 1 have come together.

The rotating part is made of a metallic material.

As we can see in Figure 1, the balancing device 2 comprises a frame or frame 6 which is intended to receive the rotating part 1. The latter is intended to rotate around its longitudinal axis X and relative to the frame ( which is then fixed). The rotating part 1 here is a hollow shaft (such as a low pressure or high pressure shaft of the turbomachine) which extends along the longitudinal axis between a first end 7 and a second end 8. For this purpose, the device 2 comprises at least one guide bearing configured to guide the rotating part in rotation. In the present example, two guide bearings are supported by the frame. A first bearing 9 is located at the level of the first end 7 of the shaft and a second bearing 10 is located at the level of the middle part of the shaft (between the first end and the second end). Alternatively, the second bearing 10 is placed at the level of the second end 8 of the shaft.

The balancing device 2 comprises a rotating element 11 for setting the rotating part. The rotator 11 in the present example is a motor which is configured to rotate the hollow shaft about its longitudinal axis X at a predetermined speed. The motor can be a heat engine or an electric motor. The motor is advantageously fixed to the frame 6 of the balancing device. The predetermined speed is of the order of a hundred revolutions per minute.

At least one balancing element is mounted on the frame so as to correct the unbalance (s) of the rotating part 1. In the present example, the balancing element comprises a machining element 12 configured so as to machine the bead of material 5 of the rotating part 1 in the event of an unbalance. The machining element 12 is mounted on the frame 6 so as to be oriented towards the non-functional surface of the rotating part.

The guide bearings 9, 10 are advantageously remote from the machining element 12.

The machining element 12 is advantageously mounted to move along an axis perpendicular to the longitudinal axis of rotation of the rotating part. However, the machining element is immobilized in rotation relative to the frame. In the present example, this is a translation along the radial axis R. Also advantageously, the machining element 12 comprises an abrasive element such as a grinding wheel 15. The latter extends from a distal end of the grinding wheel. frame along the radial axis. The grinding wheel 15 has in the present example a generally conical shape of revolution, the apex (or point) of which oriented towards the bead of material has a small contact surface. The grinding wheel 15 is thin enough to control the correction of the unbalance and here the removal of material at the level of the material bead 5. The contact surface between the rotating part and the grinding wheel is reduced so as to guarantee precise balancing of the unbalance. In particular, the size of the grinding wheel 15 must be adapted to the tolerances on the unbalance.

We will now describe the operation of the rotating part balancing process in relation to Figures 2a, 2b, 2c, 3a, 3b and 3c. The advantage of this method is that if the rotating part 1 has an unbalance, it will deform along a straight line parallel to the direction of the unbalance and the balancing device 2 can automatically balance or correct the unbalance by machining the bead. of material 5 at the point of unbalance.

As we will see later, machining depends on the speed of rotation of the rotating part and the frequency of the vibration mode.

For this, the rotating part 1 equipped with the bead of material 5 is installed on the balancing device 2 described above. The bead of material 5 is annular. Part 1 is in a neutral position, that is to say that its longitudinal axis O is coaxial with the axis of rotation of the motor as can be seen in FIG. 2a in particular.

The balancing device 2 and the rotating part 1 equipped with the bead of material 5 have a predetermined natural mode ω of vibration and a frequency fo of the predetermined natural mode of vibration (for a predetermined speed of rotation). We consider here only the natural bending mode and the frequency of the natural bending mode of the balancing device and rotating part assembly. Regarding the balancing device, we mainly consider chassis 6.

Of course, the assembly (balancing device and rotating part) can be subjected to other natural modes of vibration associated with frequencies of natural modes of vibration such as torsion modes, etc.

The eigenmode (bending) and the predetermined eigenmode frequency are known to the operator and / or are recorded in an electronic control unit of the balancing device. In particular, the value of the predetermined vibration mode frequency is stored in a memory of the electronic control unit. Advantageously, but without limitation, these modes and frequencies are obtained beforehand by calculation. Tests can then take place to confirm the values obtained by calculation. It is understood as we will see it later that if the machining is carried out from the outside then the frequency of rotation must be lower than the frequency of the vibration mode and if the machining is carried out from the inside then the frequency of rotation must be greater than the frequency of the vibration mode.

Prior to the rotation of the rotating part, the displacement (and therefore the speed of rotation) is zero (equal to 0) as we can see in FIGS. 2a and 3a. In this state, the fault of the part is unknown, in particular, the operator does not know if there is an imbalance.

The rotating part 1 is then rotated at a rotation frequency f different (higher or lower) from the frequency of the vibration mode fo (natural bending mode) of the assembly (balancing device with the rotating part) . In this exemplary embodiment, the frequency of rotation of the rotating part depends on the position of the bead of material 5 on the rotating part. To this end, the operator will establish a step of verifying the position of the bead of material on the rotating part before it is rotated.

The method comprises a step of balancing the part by machining a portion of the bead of material 5 at the location of a deformation of the part corresponding to an unbalance.

In the case of Figures 2a to 2c, the part comprises an unbalance 13 (shown schematically by a surplus of material) which is located towards the inside of the shaft (the rotating part 1) and the bead of material 5 is located, as we have seen previously, on a portion of the radially outer surface 3 of the hollow shaft. The unbalance 13 is located at noon (by analogy to the face of a clock) on the radially outer surface 3 of the shaft (by analogy to the face of a clock). In Figure 2a, the axis of the shaft is in a neutral position (that is, the axis of the shaft is coaxial with the axis of the motor). The shaft is rotated by the motor and at low speed relative to the grinding wheel 15. In this case, the frequency of rotation f is not zero. The frequency of rotation f of the rotating part is lower than the frequency of the vibration mode fo of the balancing device and the hollow shaft. The grinding wheel 15 extends radially outside the shaft.

In the rotating frame of the balancing device, the rotating part and balancing device assembly move along a line D parallel to the direction of the unbalance of the rotating part (since the balancing device is very well balanced). In fact, the balancing of the device is less than 1 gram centimeter. The grinding wheel here approaches the rotating part, from the outside thereof, opposite the bead of material 5 and simultaneously. Likewise, the axis O (which is also the axis X) of rotation of the shaft moves in a direction defining the vector Vb of the unbalance. We can say that the part is deformed according to the direction of the vector Vb of the unbalance during the rotation of this one. The axis of rotation after deformation O "is radially offset from the axis O. A mode is innate to a part whether there is unbalance or not. On the other hand, the presence of an unbalance amplifies the mode, and therefore its distortion. It should be noted that the grinding wheel moves but at a time scale much greater than the rotation of the shaft. For example, the grinding wheel moves in translation along the radial axis R at a speed between 10 and 500 µm / s. The movements of the grinding wheel and the shaft are independent of each other. The bead of material is machined as long as the part deforms during rotation.

In Figure 2c, the contact between the grinding wheel and the shaft is in the direction of the workpiece unbalance. The displacement or the deformation after machining becomes zero because the unbalance has been corrected. The bead of material 5 includes localized machining 14 and the shaft is corrected. The shaft refocuses on the axis of rotation of the motor and machining ceases.

In the embodiment of FIGS. 3a to 3c, the bead of material 5 is located on the radially internal surface of the hollow shaft and an unbalance 13 is located in the vicinity of a portion of the radially internal surface 4. The grinding wheel is installed inside the shaft.

In Figure 3a, the longitudinal axis X of rotation of the shaft is in the neutral position. The unbalance is located at noon on the radially outer surface of the shaft (by analogy with a clock face). Figure 3b shows the shaft which is rotated around its axis at high speed relative to the grinding wheel 15. In this case, the rotation frequency f of the shaft is greater than the frequency of the vibration mode fo of the grinding wheel. balancing device and the rotating part of a turbomachine. The rotating part is deformed in a direction opposite to that of the unbalance vector Vb. Simultaneously, the grinding wheel here approaches the radially internal surface, opposite the bead of material 5 following a radial displacement. The contact between the grinding wheel and the shaft (in particular the bead of material 5) to be balanced is made in the direction of the unbalance vector Vb. In FIG. 3c, the bead of material comprises localized machining 14 in the direction of the unbalance. The shaft and the grinding wheel are re-centered on the axis of rotation of the motor.

In figure 4, we see that as long as the frequency of rotation of the part is much lower than the frequency of the vibration mode of the rotating part, the displacement of the rotating part (here the hollow shaft) is in phase with the unbalance. Above the vibration frequency, the movement of the grinding wheel is out of phase with the unbalance. Depending on the constraints (spatial for example), the bead of material 5 can be placed inside or outside the rotating part. Depending on the choice, the rotating part will have to turn at a frequency lower than f0 (bead outside) or greater than f0 (bead inside).

Claims (10)

Device (2) for balancing a rotating part (1) of an aircraft turbomachine comprising:

• a frame (6) capable of receiving the rotating part (1) movable in rotation along an axis of rotation X relative to the frame, the rotating part (1) being equipped with a bead of material (5),
• at least one guide bearing (9, 10) in rotation of the rotating part (1),
• an element for rotating (11) the rotating part (1) around the axis of rotation, and
• at least one machining element (12) mounted on the frame movably along a radial axis R perpendicular to the axis of rotation of the rotating part, the machining element (12) being configured so as to machine the bead of material (5) when the rotating part (1) moves towards the machining element along a straight line parallel to a direction of an unbalance vector (Vb) and at the location of the unbalance.

Balancing device (2) according to the preceding claim, characterized in that the machining element (12) moves in translation along the radial axis R at a speed of between 10 and 500 µm / s. A balancing device (2) according to any one of the preceding claims, characterized in that the machining element (12) comprises an abrasive element such as a grinding wheel (15). Balancing device (2) according to any one of the preceding claims, characterized in that the rotating element (11) is a motor. Method for balancing a rotating part (1) of an aircraft turbomachine, the method comprising the following steps:

• installation of the rotating part (1) which is hollow and which is equipped with a bead of material (5) on a balancing device (2) according to any one of the preceding claims,
• rotation of the rotating part along an axis of rotation at a rotation frequency (f) different from a predetermined frequency of the vibration mode (fo) of the balancing device and of the rotating part,
• balancing of the rotating part by machining a portion of the bead of material when the part moves towards the machining element in a direction corresponding to an unbalance vector (Vb) and to the location of the unbalance.

Method according to the preceding claim, characterized in that the rotating part (1) is manufactured beforehand with the bead of material (5), in one piece. Method according to any one of Claims 5 and 6, characterized in that the bead of material (5) is arranged on a non-functional surface of the rotating part and facing the machining element, and in that the frequency of rotation of the rotating part depends on the position of the material bead on the rotating part. Method according to one of claims 5 to 7, characterized in that the rotating part (1) rotates at a frequency of rotation (f) lower than the frequency of the predetermined vibration mode (f0) if the bead of material (5) is disposed on a radially outer surface of the rotating part. Method according to one of claims 5 to 7, characterized in that the rotating part (1) rotates at a frequency of rotation (f) greater than the frequency of the predetermined vibration mode (f0) if the bead of material (5) is disposed on a radially internal surface of the rotating part. Turbomachine rotating part which has been balanced with a balancing method according to any one of claims 5 to 9.