FR2995019A1 - TURBOMACHINE COMPRISING A DEVICE FOR MEASURING THE AXIAL DISTANCE BETWEEN A STATOR PIECE AND A ROTOR PIECE OF THE TURBOMACHINE - Google Patents

Abstract

An aircraft turbomachine (1) extending axially along an axis (X) and comprising a stator part (2) and a rotor part (3) adapted to be rotated about the axis (X) relative to to the stator part (2), the turbomachine comprising a device (4) for measuring the axial distance between the stator part (2) and the rotor part (3), a turbomachine in which the measuring device (4) ) having a cylinder (5) defining at least one main compartment (C) filled with fluid in which is mounted a movable piston (6), the cylinder (5) is integral with one of the parts (2, 3) and the piston mobile (6) is adapted to be moved by the other of said pieces (2, 3).

Description

[0001] The present invention relates to the field of adjustment of axial clearances between mechanical parts of a turbomachine, and to a device for measuring the axial distance between a piece of stator and a rotor part of the turbomachine. extending axially. Axial clearance measurement is an important step when creating a new turbomachine, in particular an aircraft turbojet engine in which an upstream flow flows downstream. If the axial clearance between two mechanical parts of the turbomachine is too great, it increases leaks and decreases the efficiency of the turbomachine. In addition, excessive axial clearance increases the overall size of the turbomachine and therefore its mass, which has a disadvantage. On the contrary, if the axial clearance between two mechanical parts of the turbomachine is too low, the parts can come into contact due to thermal expansion which can be critical, for example, when a rotor part of the turbomachine comes into contact with a stator piece. In order to optimize the axial clearances, these must be measured accurately, in particular when the turbomachine is active.

Several methods for measuring axial clearances are known in the prior art. A first method is to perform a "super-X shot", that is to say, an X-ray X-ray of the turbomachine to observe the axial play between two mechanical parts at the time of the X-ray. In addition to its harmful impact on the environment, this first method has the disadvantage of, on the one hand, requiring significant test means (shielding, etc.) and, on the other hand, of not allowing to obtain only a point measurement of the axial play which does not allow to determine if a critical axial play appears over time.

A second method is to use wear indicators which are placed on a mechanical rotor part for which it is desired to know the axial clearance with respect to another mechanical piece of stator. When the turbomachine is active, the mechanical rotor part rotates while the mechanical stator part remains static by definition. Due to the thermal expansion during operation, the axial clearance between the mechanical parts can decrease and lead the wear indicators to rub against the mechanical stator part. Once the turbomachine off, it must be removed to access the wear indicators to determine their thickness after wear, this thickness corresponding to the minimum axial clearance between the two mechanical parts. In addition to the time and difficulty of dismantling the turbomachine, this second method only measures the minimum axial clearance between two mechanical parts. The second method does not allow to follow the axial play over time.

A third method is to use the capacitive phenomenon between two mechanical parts in order to deduce the axial play, the capacity being inversely proportional to the axial play between the mechanical parts. The third method makes it possible to follow the axial clearance over time but is only applicable for low-end axial play, of the order of one millimeter. By way of example, a double-body turbomachine comprises a low-pressure body and a high-pressure body. The low pressure rotor of the low pressure body, that is to say a rotor part, is traditionally separated from an exhaust casing of the turbomachine, that is to say a stator piece, by a set axial of several millimeters. The methods according to the prior art do not make it possible to follow such axial clearance over time, which presents a drawback. GENERAL PRESENTATION OF THE INVENTION To eliminate at least some of these drawbacks, the invention relates to an axially axially extending aircraft turbine engine comprising a stator piece and a rotor part adapted to be rotated around the axle. axis with respect to the stator part, the turbomachine comprising a device for measuring the axial distance between the stator part and the rotor part, a turbomachine in which, the measuring device comprising a cylinder defining at least one main compartment filled with fluid in which is mounted a movable piston, the cylinder is integral with one of the parts and the movable piston is adapted to be moved by the other of said parts. With the device according to the invention, the axial displacement of the rotor part relative to the stator piece is measured indirectly by detecting the displacement of the piston in the main compartment. This measurement is advantageously continuous and there is no constraint on the value of the measured axial difference. Such a device is thus adapted to measure the axial distance between a rotor shaft and an exhaust casing of a turbomachine.

Preferably, the movable piston extends along the axis of the turbomachine so as not to undergo tangential forces relative to the centrifugal force which improves its life while improving its accuracy. More preferably, the piston dividing the main compartment into a first chamber and a second chamber, the measuring device comprises means for measuring the fluid pressure of at least one of the chambers of the main compartment. By measuring the fluid pressure, an indirect measurement of the displacement of the piston is obtained. This thermodynamic measurement is simple to implement in a turbomachine subjected to high pressures and high temperatures. Still preferably, the fluid pressure measuring means is configured to measure the fluid pressure in both chambers of the main compartment. Thus, the measuring device is compact.

Preferably, the measuring device comprising an auxiliary chamber filled with fluid, the pressure measuring means are configured to measure the fluid pressure of the auxiliary chamber. Thanks to the auxiliary chamber, the pressure measuring means can obtain a reference pressure and thus deduce the axial distance between the rotor part and the stator part by eliminating the temperature parameter.

According to one aspect of the invention, the auxiliary chamber is configured externally to the cylinder. According to another aspect of the invention, the auxiliary chamber is configured internally to the cylinder.

Preferably, the cylinder is integrally mounted to the stator piece so as to avoid the creation of an unbalance of the rotor part. Preferably, the measuring device comprises stop means adapted to cooperate with a free end of the piston. Such abutment means make it possible to adjust the initial position of the piston in order to calibrate the measuring device. Preferably, the measuring device comprises elastic means adapted to drive the piston out of the cylinder so as to ensure permanent contact, and to allow measurement of the axial distance over a large range of length which is a function of the length of the piston . Preferably, the stop means are integrally mounted to the rotor part. Due to their low mass and their small size, the stop means do not generate unbalance.

PRESENTATION OF THE FIGURES The invention will be better understood on reading the description which will follow, given solely by way of example, and referring to the appended drawings in which: FIG. 1 is a diagrammatic representation in axial section of a first embodiment of a device for measuring an axial distance for a turbomachine according to the invention; Figure 2 is a schematic representation in axial section of the stator part of the turbomachine of Figure 1 on which is mounted a cylinder with a movable piston; Figure 3 is a schematic representation in axial section of the rotor part of the turbomachine of Figure 1 on which are mounted stop means; Figure 4 is a schematic close representation of the cylinder of Figure 2; Figure 5A is a schematic representation of the measuring device of Figure 1 when the rotor part and the stator part of the turbomachine are axially close; FIG. 5B is a schematic representation of the measuring device of FIG. 1 when the rotor part and the stator part of the turbomachine are spaced apart axially, and FIG. 6 is a schematic representation in axial section of a second form of FIG. embodiment of a device for measuring a turbomachine according to the invention.

It should be noted that the figures disclose the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DESCRIPTION OF ONE OR MORE EMBODIMENTS AND IMPLEMENTATION FIG. 1 represents a view in axial section of a turbomachine according to the invention which extends along an axis X. Thereafter, the terms "upstream" and "Downstream" are defined with respect to the direction of gas flow in the turbomachine, from upstream to downstream.

With reference to FIG. 1, the turbomachine 1 comprises a stator piece which, in this example, is in the form of an exhaust casing 2 of the turbomachine 1 comprising a lubricant injector 20, also referred to as a cane. injection, mounted axially along the axis X of the turbomachine 1. It goes without saying that the invention applies to any stator part, that is to say, to any non-rotating part in the reference of the turbomachine 1. It goes without saying that the stator piece can expand during the operation of the turbomachine. Still with reference to FIG. 1, the turbomachine 1 comprises a rotor part which, in this example, is in the form of a rotor shaft 3 of the turbomachine 1 extending along the axis X, preferably a low pressure rotor shaft for a double-body turbomachine. The rotor shaft 3 comprises at its downstream end an annular sleeve 30 as illustrated in FIG. 1. The rotor shaft 3 is adapted to be rotated about the axis X with respect to the stator casing 2. axial distance between the rotor shaft 3 and the stator housing 2 must be monitored to optimize the mass and size of the turbomachine 1 as detailed previously in the preamble. For this purpose, the turbomachine comprises a device 4 for measuring the axial distance between the stator housing 2 and the rotor shaft 3. Preferably, the axial distance AX measured corresponds to a variation of the axial distance with respect to an axial reference position. Figure 1 shows the stator housing 2 and the rotor shaft 3 in this reference axial position. According to the invention, with reference to FIG. 2, the measuring device 4 comprises a cylinder 5 defining at least one main compartment Cp filled with fluid in which is mounted in axial translation a movable piston 6. In this example, the cylinder 5 is secured to the stator housing 2 and the movable piston 6 is adapted to be displaced by the rotor shaft 3. In other words, when the axial distance changes between the rotor shaft 3 and the stator housing 2, the movable piston 6 moves axially in the cylinder 5 which allows to measure the evolution of the axial distance. The cylinder 5 is integral with the stator housing 2 in order to limit the unbalance of the rotor shaft 3, but it goes without saying that it could be secured to the rotor shaft 3.

Referring to Figure 2, the cylinder 5 is in the form of an axial envelope defining internally a main compartment Cp filled with fluid, for example, air. The movable piston 6 extends along the axis X and has a guide end 61 which is mounted in the main compartment Cp of the cylinder 5 and a contact end 62 which is adapted to be in contact with abutment means 9 which are integral with the rotor shaft 3 as illustrated in FIG. 1. Preferably, with reference to FIG. 1, the cylinder 5 extends axially and is fixed to the upstream end of the injection rod 20 which is integral with the stator housing 2. The stop means 9 are preferably fixed at the center of the sleeve 30 of the rotor shaft 3.

With reference to FIG. 3, the abutment means 9 comprise a threaded prick 91 fixed to the center of the sleeve 30, on which is screwed axially a threaded contact nut 92. Preferably, in order to adjust the axial position of the contact nut 92, an adjusting ring 93 is mounted between the threaded stinger 91 and the threaded contact nut 92 as illustrated in FIG.

As illustrated in FIG. 1, the measuring device 4 comprises elastic means 8, preferably an elastic spring 8, adapted to drive the movable piston 6 out of the cylinder 5, that is to say, against the abutment means 9. Thus, if the axial gap increases between the stator housing 2 and the rotor shaft 3, the free end 62 of the piston 6 remains in contact with the contact nut 92 due to the action of the spring 8. The contact between the contact nut 92 and the contact end 62 of the piston 6 is limited to a reduced surface to prevent the occurrence of friction. As illustrated in FIG. 4, the main compartment Cp of the cylinder 5 defines a first chamber C1 and a second chamber C2 which are separated by the guide end 61 of the mobile piston 6. In this example, the guide end 61 of the movable piston 6 is in the form of a pallet 61 of section substantially equal to that of the section of the main compartment C. In this example, the pallet 61 comprises a seal 63, preferably a quadrilobe seal 63, so as to prevent any flow of fluid between the two chambers C1, C2 of the main compartment C. More preferably, the piston 6 may comprise a plurality of seals 63 so as to avoid any leakage of fluid from the chambers C1, C2 of the main compartment C. In this example, with reference to FIG. 2, the measuring device 4 comprises at least one auxiliary chamber Ca filled with fluid, preferably of the same type of fluid as that chambers C1, C2 of the main compartment C. Preferably, the auxiliary chamber Ca and the chambers C1, C2 of the main compartment Cp are close, preferably, adjacent so that the temperature conditions are identical for the rooms C1 , C2, Ca in the turbomachine 1. Referring to FIG. 4, the auxiliary chamber Ca is attached to the rear end of the cylinder 5 so as to be separated only by a simple wall of the second chamber C2 of the main compartment. C. Thus, within the turbomachine 1, the fluid of the second chamber C2 of the main compartment Cp and the fluid of the auxiliary chamber Ca have the same temperature T. For an aircraft turbine engine, the temperature T is equal to order of 100 ° C. With reference to FIG. 1, the measuring device 4 comprises means 7 for measuring the fluid pressure. The measuring means 7 are connected to the second chamber C2 of the main compartment Cp of the cylinder 5 and to the auxiliary chamber Ca as shown in FIG. in FIG. 2, the pressure measuring means 7 are connected to the auxiliary chamber Ca by a first pipe 71 and to the second chamber C2 of the main compartment Cp by a second pipe 72 as illustrated in FIG. In this example, the pressure sensor 7 is in the form of at least one piezoelectric sensor, but it goes without saying that other sensors could also be suitable. The pressure measuring means 7 are adapted to calculate the difference between the pressure P2 measured in the second chamber C2 and the pressure Pa measured in the auxiliary chamber Ca. Indeed, as will be presented in the example of implementation of the invention, any displacement of the movable piston 6 in the main compartment Cp of the cylinder 5 results in a modification of the volume V2 of the second chamber C2 which modifies the pressure P2 of the fluid in the second chamber C2. The pressure Pa measured in the auxiliary chamber Ca fulfills a reference pressure function and allows a relevant analysis of the evolution of the pressure P2 in the second chamber C2 while avoiding the evolution of the temperature T within the 1. Referring to FIG. 1, the pressure measuring means 7 are connected to a computer (not represented) by communication cables 10 so as to make it possible to compare the pressures Pa, P2 and thus to determine the evolution. the axial distance AX between the stator housing 2 and the rotor shaft 3 as will be presented later.

Referring to Figure 1, in its reference axial position, the guide end 61 of the movable piston 6 is positioned so that the measured pressures P2, Pa are equal. In this example, the chambers Ca, C2 are filled with the same fluid, preferably air. So that the measured pressures P2, Pa are equal to the initial state, the volume V of the auxiliary chamber Ca is the same as the volume V2 of the second chamber C2 when the piston 6 is in its initial state. In addition, preferably, the first pipe 71 and the second pipe 72 have the same volume. Thus, any variation of the volume V2 of the second chamber C2 causes a pressure difference with respect to the pressure Pa measured in the auxiliary chamber Ca.

The reference axial position of the measuring device 4 is shown in FIG. 5A. In this example, the guide end 61 of the movable piston 6 separates the main compartment Cp so that the volume V2 of the second chamber C2 is equal to the volume V of the auxiliary chamber Ca.

Preferably, the axial thickness of the adjusting ring 93 of the abutment means 9 is chosen so as to allow precise adjustment of the axial position of the contact nut 92 so as to position the guide end 61 of the piston 6 at the reference axial position. The invention will now be presented for an exemplary implementation of the invention in which the stator housing 2 and the rotor shaft 3 deviate axially from one another. In the initial state, the turbine engine 1 is stopped, the rotor shaft 3 being stationary relative to the stator housing 2. As illustrated in FIG. 5A, the piston 6 is stationary in the main compartment Cp of the cylinder 5, its free end 62 being in abutment against the contact nut 92 due to the force directed upstream applied to the piston 6 by the elastic spring 8. In this initial state, the measured pressure Pa, Pp are identical. When the turbomachine 1 is activated, the rotor shaft 3 rotates around the axis X with respect to the stator housing 2. During operation, due to expansion and axial clearances, the rotor shaft 3 moves axially with respect to the stator housing 2. In the example of FIG. 5B, the rotor shaft 3 moves away from the stator housing 2 by an axial distance X. The elastic spring 8 moves the piston 6 towards the upstream so that its free end 62 remains in abutment with the contact nut 92 which deviates from the cylinder 5. The displacement of the piston 6 is reflected more particularly by a displacement upstream of its guide end 61 which increases the volume V2 of the second chamber C2 in the main compartment Cp as shown in Figure 5B. The fluid contained in the second chamber C2 has the same temperature T as the fluid contained in the auxiliary chamber Ca because of the proximity of said chambers Ca, C2. Also, as the volume V2 of the second chamber C2 increases, it follows that the pressure P2 in the second chamber C2 decreases. In other words, the pressure P2 and the reference pressure Pa are no longer equal. The pressure difference AP is measured by the measuring means 7 and then transmitted to the computer so that it deduces the axial displacement AX of the piston 6.

In more detail, according to the ideal gas law, the volume of fluid in a chamber can be written: (1) Pk * T IV with k a predetermined constant If this law is applied to the second chamber C2, we obtain: (2) P2 = k * T2 / V2 If this law is applied to the auxiliary chamber Ca, we obtain: (3) Pa = k * TalVa As the two chambers Ca, C2 are close to one another, As a result, their temperatures are identical (Ta = T2). We deduce the following relation: (4) P2 - Pa * Va V2 Thus, if the conditions remain unchanged in the auxiliary chamber Ca, the pressure its volume V2 increases.

As indicated above, the measuring means 7 make it possible to measure the pressure ratio AP between the two chambers Ca, C2. The pressure ratio AP is here equal to pa / P21. The volume V of the cylindrical chamber C is equal to its section S by its length L. (5) V = S * LA the initial state, the length of the second chamber C2 corresponds to an initial length L2 defined when the volumes V2 and V, are equal. In operation, the length of the second chamber C2 corresponds to the initial length L2 to which is added an axial variation AX which is the desired value. Thus, by equation (5), the following relation is obtained: P2 decreases if (6) V2 = S2 * (L2 ± AX) = ± S2 * 3, X with Va = S2 * L2 for the axial position of reference chamber volume V, the auxiliary chamber Ca is known as well as the section S2 of the second C2. Thanks to relations (4) and (6), we deduce: (7) P * VP * V paaaa 2 V2 Va ± S2 * AX (8) Va + S2 * AX - Pa * Va P2 (9) 1 (P * V a = aa S2, P2 S2 The knowledge of the pressure difference .A / 3 and the initial length L2 and allows the computer to obtain directly and accurately the axial displacement value AX which is very advantageous .

Unlike other measuring devices of the prior art, the axial displacement AX is measured continuously, in real time and without constraints on the value of the axial difference. Advantageously, the measuring device 4 according to the invention can be transposed to other parts of the turbomachine 1.

The use of an auxiliary chamber Ca makes it possible to overcome the temperature conditions that are variable within the turbomachine 1. This provides a measuring device of simple design which increases its reliability and maintenance. The pressure variations, due respectively to the temperature variation and to the displacement of the piston, are of the order of one hundred millibars, such pressure variations being measurable by a piezoelectric sensor 7. It should be noted that can reduce pressure variations due to temperature variations by insulating the parts of the device or by using low-conductive materials.

Second Embodiment A second embodiment of the invention is described with reference to FIG. 6. The references used to describe elements of structure or function that are identical, equivalent or similar to those of the elements of FIG. 1 are the same, to simplify the description. Moreover, the entire description of the embodiment of Figure 1 is not repeated, this description applies to the elements of Figure 6 when there are no incompatibilities. Only notable differences, structural and functional, are described. Referring to Figure 6, the measuring device 4 has no auxiliary chamber Ca outside the cylinder 5 as a reference chamber. Indeed, the measuring means 7 are connected, on the one hand, to the first chamber C1 and, on the other hand, to the second chamber C2 of the main compartment C. In other words, the first chamber C1 performs the chamber function Ca reference to allow to deduce the axial displacement X. According to this embodiment, the auxiliary chamber Ca is configured internally to the cylinder 5. For this purpose, with reference to Figure 6, the pressure measuring means 7 comprise a pipe 73 connected to the first chamber C1 and a second pipe 72 connected to the second chamber C2. Preferably, the sections of the pipes 72, 73 can be varied so that they have different lengths but identical volumes.

In this embodiment, it is further necessary to know the section of the piston rod 6 in order to correlate the axial displacement of the piston 6 with the volume V1 of the first chamber C1. Advantageously, the fluid of the two chambers C1, C2 have the same temperature because of their proximity. In addition, similarly, the reference axial position of the movable piston 6 is defined when the pressure P1 in the first chamber C1 is equal to the pressure P2 in the second chamber C2.

Claims (10)

REVENDICATIONS1. A turbomachine (1) for an aircraft extending axially along an axis (X) and comprising a stator piece (2) and a rotor piece (3) adapted to be rotated about the axis (X) with respect to the stator part (2), the turbomachine comprising a device (4) for measuring the axial distance between the stator part (2) and the rotor part (3), a turbomachine characterized in that, the measuring device (4) comprising a cylinder (5) defining at least one main compartment (Ce) filled with fluid in which is mounted a movable piston (6), the cylinder (5) is integral with one of the parts (2, 3) and the movable piston (6) is adapted to be displaced by the other of said parts (2, 3). 2. The turbomachine (1) according to claim 1, wherein the movable piston (6) extends along the axis (X) of the turbomachine (1). 3. The turbomachine (1) according to claim 2, wherein, the piston (6) dividing the main compartment (Ce) into a first chamber (C1) and a second chamber (C2), the measuring device (4) comprises means for measuring the pressure (7) of the fluid of at least one of the chambers (C1, C2) of the main compartment (Ce). 4. The turbomachine (1) according to claim 3, wherein, the measuring device (4) comprising an auxiliary chamber (C) filled with fluid, the pressure measuring means (7) are configured to measure the fluid pressure. of the auxiliary chamber (Ca). 5. Turbomachine (1) according to claim 4, wherein the auxiliary chamber (C) is externally configured to the cylinder (5). 6. Turbomachine (1) according to claim 4, wherein the auxiliary chamber (C) is configured internally to the cylinder (5). 7. The turbomachine (1) according to one of claims 1 to 6, wherein the cylinder (5) is integrally mounted to the stator part (2). 8. Turbine engine (1) according to one of claims 1 to 7, wherein the measuring device (4) comprises stop means (9) adapted to cooperate with a free end of the piston (6). 9. The turbomachine (1) according to claim 8, wherein the abutment means (9) are integrally mounted to the rotor part (3). 10. The turbomachine (1) according to one of claims 1 to 9, wherein the measuring device (4) comprises elastic means (8) adapted to drive the piston (6) out of the cylinder (5).