FR3056747A1 - TEST SYSTEM FOR MEASURING CINEMATICS FOR DECOUPLING TWO BIT PIECES OF TURBOMACHINE - Google Patents

Abstract

The invention relates to a test system for measuring a decoupling kinematics between a structuring casing and a turbomachine part, said structuring casing and said part being coupled by a fusible element according to a link that can be broken, the test system being comprising: - a disturbance means adapted to apply a disturbance on a rotor supported by the structuring casing, - a measuring means, in contact with the fuse element, measuring an electrical parameter associated with the fuse element to determine a state of the fuse element, said measurement means being dissociated from the fuse element; - analysis means for determining a delay between the disturbance applied by the disturbance means and a rupture of the fuse element.

Description

Holder (s): SAFRAN AIRCRAFT ENGINES.

Extension request (s)

Agent (s): CABINET CAMUS LEBKIRI Limited liability company.

TEST SYSTEM FOR MEASURING A KINEMATICS OF DECOUPLING OF TWO BOLT PARTS OF TURBOMACHINE.

FR 3 056 747 - A1 yY} The invention relates to a test system for measuring a decoupling kinematics between a structuring casing and a turbomachine part, said structuring casing and said part being coupled by a fusible element in a connection suitable for be broken, the test system comprising:

a disturbance means adapted to apply a disturbance to a rotor supported by the structuring casing,

a measurement means, in contact with the fuse element, measuring an electrical parameter associated with the fuse element to determine a state of the fuse element, said measurement means being dissociated from the fuse element,

- Analysis means for determining a delay between the disturbance applied by the disturbance means and a rupture of the fuse element.

TEST SYSTEM FOR MEASURING A KINEMATICS OF DECOUPLING OF TWO BOLT PARTS OF TURBOMACHINE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the general field of turbomachinery. It relates more particularly to a test system for measuring a decoupling kinematics of two bolted parts of a turbomachine, for example a structuring casing and an upstream bearing support. Such a system is used, for example, during certification tests of the turbomachine.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

A turbomachine conventionally comprises a gas turbine composed of a plurality of stages of fixed blades constituting a stator, and of a plurality of stages of movable blades constituting a rotor mounted on a shaft. The rotor shaft is centered and guided in rotation by bearings held by supports, said supports being connected to a structuring casing surrounding the rotor.

If a rotor blade breaks or becomes detached, for example following a bird ingestion, a significant imbalance appears on the shaft, which generates loads that the bearing supports communicate with the structuring casing, with significant risks of deterioration of the turbomachine.

To avoid the transmission of excessive loads between the bearing supports of the fan and the structuring casing linked to the suspensions of the turbomachine such as the inlet casing, it is known to couple them by fusible elements, which break when the load applied to them exceeds a threshold value. Depending on the type of bearing support architecture of the engine of the turbomachine, the decoupling can be done on the upstream bearing support or on the downstream bearing support of the fan.

The patent document FR 2 976 623 describes so-called “fuse” screws intended to couple an upstream bearing support and a downstream bearing support, along a connection capable of being broken under the effect of excessive loads. The upstream bearing support being connected to the structuring casing via the downstream bearing support, if a significant load is applied to the upstream bearing support, the fusible screws break one after the other so as to decouple the upstream bearing support from the structuring casing and thus avoid the transmission of the load to the structuring casing.

Furthermore, fusible screws can also be used to couple two fixed casings of a turbomachine which extend axially one after the other. For example, the patent document FR 1558212 describes the use of fusible screws to link two fixed casings: one of the casings is a structuring casing (rear turbine casing) linked to the suspensions of the turbomachine while the other casing (exhaust cone, nozzle, air intake sleeve) is cantilevered with respect to these suspensions and can transmit significant loads when it is requested on one of its natural vibration frequencies.

As part of turbomachine certification tests, for example a fan blade loss test, knowing the kinematics of decoupling of the two bolted parts of the turbomachine, in particular the instants and the order of rupture of the fusible screws, would allow to precisely estimate the evolution of the loads applied to the fusible screws, in order to size them optimally.

Currently, there is no system allowing to measure with precision the kinematics of the decoupling by fusible screws of two bolted parts of turbomachine.

GENERAL DESCRIPTION OF THE INVENTION

Thus, according to a first aspect, the invention relates to a test system for measuring a decoupling kinematics between a structuring casing and a part of a turbomachine, said structuring casing and said part being coupled by a fuse element according to a connection capable of being broken, the test system comprising:

a disturbance means adapted to apply a disturbance to a rotor supported by the structuring casing,

a measuring means, in contact with the fusible element, measuring an electrical parameter associated with the fusible element to determine a state of the fusible element, said measuring means being dissociated from the fusible element,

- analysis means to determine a delay between the disturbance applied by the disturbance means and a rupture of the fusible element.

The term “structuring casing” means a casing linked to the suspensions of the turbomachine.

In addition, "state" of the fusible element means a state in which the fusible element is broken or a state in which the fusible element is not broken.

The test system according to the first aspect of the invention makes it possible to solve the aforementioned problems.

In fact, when the disturbance means applies a disturbance to the rotor such that the stress on the fusible element exceeds a threshold value, said fusible element breaks. The rupture of the fusible element then generates a variation in the electrical parameter characteristic of said rupture measured by the measurement means in contact with said fusible element. By analyzing the variation of the electrical parameter, it is then possible to know when the break takes place and thus to deduce the delay between the disturbance on the rotor and the break of the fusible element.

Advantageously, the structuring casing and the part are coupled by a plurality of fusible elements associated with one or more measurement means which makes it possible to determine the time interval between two ruptures of fusible elements as well as the order of decoupling of the fusible elements. The determination of the instants of rupture of the fusible elements, the time intervals between two ruptures as well as the order in which the fusible elements rupture makes it possible to precisely estimate the evolution of the loads applied to the fusible elements and thus to dimension them in a way optimal in order to prevent premature deterioration of the turbomachine.

In addition, the measuring means is dissociated from the fusible element, so that series fusible screws can be used to carry out certification tests of the turbomachine by reproducing the actual conditions of rupture of the fusible element.

Furthermore, in addition to the characteristics which have just been mentioned in the previous paragraph, the test system according to the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations.

In a nonlimiting embodiment, the measurement means comprises a piezoelectric element, the electrical parameter measured being an electrical potential.

In a nonlimiting embodiment, the piezoelectric element is disposed between a screw head of the fusible element and the part forming a support surface for the screw head.

In a nonlimiting embodiment, the piezoelectric element is disposed between the structuring casing and the part.

In a nonlimiting embodiment, the measuring means comprises an electrical circuit to which an electrical resistance is connected, the electrical parameter being an electrical resistance.

In a nonlimiting embodiment, the electrical resistance of the electrical circuit is in contact with a screw head of the fusible element and the part forming a support surface for the screw head.

In addition, according to a second aspect, the invention relates to a test system for measuring a decoupling kinematics between a structuring casing and a part of a turbomachine, said structuring casing and said part being coupled by a first fusible element and a second fuse element, the test system comprising:

a disturbance means adapted to apply a disturbance to a rotor supported by the structuring casing,

a first measurement means, placed in contact with the first fuse element, measuring an electrical parameter associated with the first fuse element to determine a state of the first fuse element, said first measurement means being dissociated from the first fuse element,

a second measurement means, placed in contact with the second fuse element, measuring an electrical parameter associated with the second fuse element to determine a state of the second fuse element, said second measurement means being dissociated from the second fuse element,

- analytical means to determine:

o a first delay between the disturbance applied by the disturbance means and a rupture of the first fusible element, o a second delay between the disturbance by the disturbance means and a rupture of the second fusible element.

In a nonlimiting embodiment, the first measurement means comprises a first electrical circuit to which a first resistance is connected and the second measurement means comprises the first electrical circuit to which a second resistance is connected.

In a nonlimiting embodiment, the first measuring means comprises a first electrical circuit to which a first resistor is connected and the second measuring means comprises a second electrical circuit to which a second resistor is connected.

In a nonlimiting embodiment, the first resistance and the second resistance have equal resistances.

In a nonlimiting embodiment, the first resistance has a resistance that is different from the resistance of the second resistance.

The invention will be better understood in the light of the description which follows, and with reference to the figures whose list is given below.

BRIEF DESCRIPTION OF THE FIGURES

The figures are presented for information only and are in no way limiting. The figures show:

- in FIG. 1, a radial half-section of a zone located between a fan shaft and a casing structuring a turbomachine with double flow,

- in FIG. 2, a perspective view of an upstream bearing support on which fuse elements are positioned and an enlargement of an area of the upstream bearing support,

- in FIG. 3, a fusible element making it possible to couple and decouple the bearing support of the fan shaft and the structuring casing of FIG. 1,

in FIG. 4, a fixing element making it possible to couple the downstream bearing support and the structuring casing of FIG. 1,

- in FIG. 5, a partial schematic representation of the test system according to a first embodiment,

- in FIG. 6, a partial schematic representation of the test system according to a second embodiment,

- in FIG. 7, a partial schematic representation of the test system according to a third embodiment, in FIG. 8, a partial schematic representation of the test system according to a fourth embodiment,

- in FIG. 9, a partial schematic representation of the test system according to a fifth embodiment,

- in FIG. 10, a sectional view of an interface zone between a rear turbine casing and an exhaust cone of a turbomachine in which a test system according to the invention can be integrated and an enlargement of the interface area.

GENERAL DESCRIPTION OF THE INVENTION

Unless otherwise specified, the same element appearing in different figures has a unique reference.

The part of the double-flow turbomachine represented in FIG. 1 corresponds to a portion of fan shaft 1 of a rotor able to rotate around a longitudinal axis XX ′, and a portion of structuring casing 2. L blower shaft 1 and the structuring casing 2 are connected to each other at an upstream bearing 3 and a downstream bearing 4, via respectively an upstream bearing support 5 and d 'a downstream bearing support 6. A set of fusible elements 7 makes it possible to couple, according to a connection capable of being broken, the upstream bearing support 5 and the structuring casing 2. FIG. 2 represents a perspective view of a upstream bearing support 5 having a fixing ring 16 surrounding the fan shaft 1, with an axis of revolution the longitudinal axis XX ′ of the turbomachine. Thus, with reference to FIG. 2, the fuse elements 7 are distributed over the fixing ring 16 of the upstream bearing support 5.

FIG. 3 shows in more detail a fusible element 7, intended to hold the upstream bearing support 5 against the downstream bearing support 6 as long as no imbalance generated by a loss of blade appears at the level of the shaft of blower 1. The fusible element 7 is in the form of a fusible screw comprising a screw head 8 and a thread 9. The fusible character of the screw is characterized by a smooth portion 10 of reduced section, disposed between the head screw 8 and thread 9, so as to break when a stress greater than a threshold value is applied to it.

When the upstream bearing support 5 and the downstream bearing support 6 are coupled by the fuse element 7, the screw head 8 is in abutment against the upstream bearing support 5. Advantageously, the screw head 8 is in abutment the upstream bearing support 5 via an intermediate washer 11 as can be seen in FIG. 3, in order to protect the upstream bearing support 5. The smooth portion 10 of the fuse element 7 is then located at level of the junction between the upstream bearing support 5 and the downstream bearing support 6. Furthermore, the thread 9 of the fusible element 7 is tightened by means of a nut 26 housed in a first cavity 27 of the structuring casing 2 which is accessible through an orifice 61 formed in the downstream bearing support 6. In addition, an anti-rotation device, formed by a hexagonal orifice immobilizing in rotation the hexagonal sector 28 of the fuse element 7, can be positioned in the orifice 61 of the support downstream bearing 6.

In addition, according to an alternative embodiment, the screw head 8 has a shape adapted to avoid external intervention and thus protect a possible tightening of the fusible element 7.

Note, moreover, that the downstream bearing support 6 is fixed to the structuring casing 2 by means of fixing elements 20, an example of which is shown in FIG. 4. The fixing elements 20 are inserted by means of openings 17 formed in the fixing ring 16, which allow the passage of a tool for tightening said fixing elements 20. In certain cases, it is necessary to adapt the number of fixing elements 20 and the number of elements fuses 7 according to the forces to which the crown 16 must be subjected. Also, it may be advisable for the number of fusible elements 7 not to be equal to the number of fastening elements 20. In this case, a fusible element 7 can be interposed between two tuple fastening elements

20, for example a fusible element 7 interposed between two pairs of fixing elements as shown in FIG. 2. The fixing ring 16 surrounding the fan shaft 1 then comprises twice as many fixing elements 20 as fuse elements 7.

With reference to FIG. 4, the fixing element 20 is in the form of a fixing screw composed of a head 21 and a threaded rod 22. It is noted that, unlike the fusible elements 7, the elements fasteners 20 do not have a smooth portion 10 intended to break when a stress greater than a threshold value is applied to it because the fastening elements 20 must, on the contrary, keep the downstream bearing support 6 fixed against the structuring casing 2 In addition, for each fastening element 20, a counterbore 23 is formed in the downstream support bearing 6. The counterbore 23 allows a recess of the head 21 of each fastener 20 in the downstream support bearing 6, up to to a stop 24 which makes it possible to protect the head 21 of the fastening element 20 after the smooth portion 10 of the fusible element 7 has broken during a loss of blade. It is also noted that a second tapped cavity 25 is formed in the structuring casing 2 in order to screw the threaded rod 22 of the fixing element 20 there.

When one of the fan blades detaches from the fan, the cyclic radial force Io transmitted to the fan shaft 1 and to the upstream bearing 3 is converted into cyclic axial force on each fusible element 7. The force passing through the fuse elements 7 is then high and the fuse elements 7 are broken by traction at their smooth portions 10 when the cyclic axial force becomes sufficient, that is to say when it reaches a value greater than a threshold value. In addition, it is noted that, when a fusible element 7 is broken, generally, the other fusible elements 7 of the fixing ring 16 rupture one after the other in a single revolution of the fan shaft 1, and this , all the more easily as the overall mechanical resistance decreases constantly as the fusible elements 7 break. Thus, when all of the fusible elements 7 are broken, the upstream bearing support 5 is completely detached from the downstream bearing support 6 and therefore no longer transmits force towards the structuring casing 2. In such a situation of decoupling of the bearing support upstream 5, the upstream bearing 3 no longer allows the fan to be supported.

In order to determine the decoupling kinematics of the structuring casing 2 and the upstream bearing support 5 to determine the instant of rupture of the smooth portion 10 of a fuse element 7, the fuse element 7 is equipped with a system of test according to the invention. In fact, the more precisely the instant of rupture of the fusible element 7 and the load necessary for the rupture of the fusible element 7 are determined, the more the shape of the fusible element 7 can be optimized in order to minimize the loads applied to the engine during a loss of blade and thus, the vibrations transmitted to the structure of the aircraft. Optimizing the shape of the fusible element 7 saves mass and therefore reduces the aircraft’s fuel consumption. It should be noted that the test system according to the invention can be used to study the kinematics of decoupling of the structuring casing 2 and of a turbomachine part other than the upstream bearing support 5, such as a stator, an element of nacelle or to a downstream bearing support. More generally, the turbomachine part is a part linked to the structuring casing 2 by a bolted connection and capable of transmitting parasitic vibrations to the structuring casing 2.

The test system according to the invention comprises a disturbance means (not shown), adapted to apply, at an instant t _P , a stress on the fan shaft 1 of the rotor supported by the structuring casing 2.

The test system also includes a measurement means 12, in contact with a fuse element 7, for measuring an electrical parameter associated with the fuse element 7 in order to determine a state of the fuse element 7. It is noted that the means 12 is dissociated from the fuse element 7. Thus, the integration of such a test system does not require adapting the shape of the fuse elements 7 used in real conditions, only the intrinsic properties of the fuse element 7 are used: electrical conductivity and bearing surface. It will be recalled that by "state" of the fusible element 7 is meant a state in which the fusible element 7 is broken or a state in which the fusible element 7 is not broken. When the stress applied to the shaft 1 of the rotor exceeds a threshold value, the fusible element 7 breaks, which results in a variation of the electrical parameter measured by the measuring means 12.

In addition, the test system according to the invention comprises means for analyzing the electrical parameter (not shown), measured by the measurement means 12, which make it possible to determine a breaking time of the fuse element 7 and thus , a delay between the disturbance induced by the disturbance means and the rupture of the fuse element 7.

The measurement of the electrical parameter can be carried out by two different measurement means 12:

a measurement means 12 comprising a piezoelectric element 13, the electrical parameter measured is then an electrical potential or,

a measurement means 12 comprising an electrical circuit 15 to which an electrical resistance is connected, the electrical parameter measured then being an electrical resistance.

FIG. 5 represents a first embodiment of the test system according to the invention illustrating the case where the electrical parameter is measured by a measurement means 12 comprising a piezoelectric element 13.

According to the embodiment presented in FIG. 5, the piezoelectric element 13 is composed of two electrodes 132 surrounding a material 131 capable of being electrically polarized when it is subjected to mechanical stresses ("direct piezoelectric effect"). Each electrode 132 is connected to an electric wire (not shown) connecting the piezoelectric element 13 to a device for measuring the electric potential (not shown). By "device for measuring an electrical potential" is meant a voltmeter or else a device capable of measuring a voltage, for example a multimeter. Indeed, it is recalled that when the measurement means 12 comprises a piezoelectric element 13, the electrical parameter measured is an electrical potential, expressed in volts. The analysis means are connected to the electrical potential measuring device and allow, from the electrical potential measurements, to display a graph representing the variations of the electrical potential as a function of time. The analysis means are also connected by means of disturbance, to a sensor detecting the imbalance on the rotor or even to a camera filming the fan, in order to receive the data related to the disturbance such as the stress applied to the rotor and / or the instant of disturbance to then determine the delay between the disturbance and the rupture of the fuse element 7. According to one embodiment, the means for analyzing the electrical potential include a computer, a first cable for connecting the measuring device to the analysis means and a second cable for connecting the disturbance means, the sensor detecting the unbalance on the rotor or the camera filming the fan, to the analysis means.

Furthermore, the piezoelectric element 13 is advantageously in the form of a film. In this case, the small thickness of the piezoelectric element 13 (of the order of a few micrometers) makes it possible to cut it easily and thus to adapt its shape to the measurement to be made. Advantageously, the piezoelectric element 13 can be in the form of a piezoelectric washer. Indeed, a washer is not only simple to manufacture, but also practical to use: it suffices to place the washer around the fusible element 7 to hold it in position.

In addition, according to an alternative embodiment, the intermediate washer 11 shown in Figure 5 is itself made of a piezoelectric material to form the piezoelectric element 13. Alternatively, the intermediate washer 11 or the screw head 8 comprises a groove, for example in the form of an arc of a circle, into which the piezoelectric element 13 is inserted.

In the embodiment presented in FIG. 5, the piezoelectric element 13 is positioned between the intermediate washer 11 and the upstream bearing support 5. In another nonlimiting embodiment, the piezoelectric element 13 is positioned between the support upstream bearing 5 and the downstream bearing support 6. In another nonlimiting embodiment, the piezoelectric element 13 is positioned between the screw head 8 and the intermediate washer 11. In another nonlimiting embodiment, the piezoelectric element 13 is positioned between the screw head 8 and the upstream bearing support 5 forming a bearing surface for the screw head 8.

During a loss of blade induced by a disturbance of the rotor, the rupture of the smooth portion 10 of the fusible element 7 causes a reduction or even a disappearance of the relative contact pressures between the screw head 8, the intermediate washer 11 , the upstream bearing support 5 and the downstream bearing support 6. In the case of the embodiment presented in FIG. 5 in which the piezoelectric element 13 is interposed between the intermediate washer 11 and the upstream bearing support 5, during from the rupture of the fuse element 7, there will be no more contact between said elements. The electrical potential generated by the elimination of contact of the piezoelectric element 13 with the intermediate washer 11 and the upstream bearing support 5 then varies in a characteristic manner. The measurement of the electric potential by the piezoelectric element 13 connected to the electric potential measurement device followed by the representation of the variations of the electric potential by the means of analysis of the electric potential makes it possible to determine the instant of rupture of the fuse element 7 and to deduce the delay between the disturbance and the rupture of said fuse element 7. It is noted that the piezoelectric elements 13 are particularly well suited to carrying out very rapid dynamic measurements and therefore make it possible to quickly determine the instants of rupture of the elements fuses 7.

If FIG. 5 represents only a single fusible element 7, it should be noted that the upstream bearing support 5 is actually fixed against the downstream bearing support 6 by a plurality of fusible elements 7i to 7 _n . To determine the instant of rupture of each fuse element 7i to 7 _n and to deduce therefrom an order of rupture of the fuse elements 7i to 7 _n , a piezoelectric element 13 can be positioned in contact with each fuse element 7.

For example, taking the example of two fusible elements 7i and 72, the test system (not shown) comprises:

a disturbance means adapted to apply a disturbance to the shaft 1 of the rotor supported by the structuring casing 2 via the upstream 3 and downstream 4 bearings,

a first measurement means 12i comprising a first piezoelectric element 13i in contact with a first fuse element 7i, the first piezoelectric element 13i being connected to a first apparatus for measuring the electric potential making it possible to measure the electric potential generated by the first piezoelectric element 13,

a second measurement means 122 comprising a second piezoelectric element 132 placed in contact with a second fuse element 72, the second piezoelectric element 132 being connected to a second device for measuring the electric potential making it possible to measure the electric potential generated by the second piezoelectric element 13,

- analytical means adapted to analyze:

o the electric potential measured by the first electrical potential measuring device to determine the instant of rupture of the first fuse element 7i then a first delay between the disturbance and the rupture of said first fuse element 7i, o the electric potential measured by the second electrical potential measuring device for determining the instant of rupture of the second fuse element 72 then a second delay between the disturbance and the rupture of said second fuse element 72,

Naturally, a plurality of fusible elements 7i to 7 _n of the turbomachine, or even all of the fusible elements 7 _n of the turbomachine, can be equipped with a measurement means 12 according to the first embodiment. It is thus possible to know in what order and at what times the elements fuse 7i 7 _No break at various scenarios of the turbine engine tests. It is noted that the same electrical potential measuring device can be used for different piezoelectric elements 13i to 13n.

Figures 6 to 9 illustrate different embodiments of the test system in which the electrical parameter associated with a fuse element 7 is measured by a measuring means 12 comprising at least one electrical circuit 15 to which is connected at least one resistor 14. The electrical circuit 15 is connected to a device for measuring the electrical resistance in said electrical circuit 15. The measured electrical resistance is analyzed by analysis means making it possible to represent the variations of the electrical resistance in the electrical circuit 15 as a function of time. By "device for measuring an electrical resistance" is meant an ohmmeter or a device capable of measuring an electrical resistance, for example a multimeter.

FIG. 6 represents a sectional view, along a plane perpendicular to the longitudinal axis X-X ’of the turbomachine, of the test system according to a second embodiment.

Referring to Figure 6, a plurality of measurement means 12i to 1212 are in contact with the fuse elements 7i to 7i2 and the upstream bearing support 5 (not shown).

Each fuse element is electrically connected to a first electrical circuit 15 20 by means of a plurality of resistors 14i to 14i2. More specifically, the first electrical circuit 15 comprises a first conductive material 151 to which the resistors 14i to 14i2 are connected in parallel. The screw heads 8, which are in contact with the resistors 14i to 14i2, are connected to a mass formed by the upstream bearing support

5. The first circuit 15 further comprises a second conductive material 152 25 connecting the ground to the device for measuring the electrical resistance.

Note that in the second embodiment all the resistors 14i to 14i2 have equal electrical resistances.

Thus, when a first fusible element 7i is subjected to a stress which exceeds a threshold value, the smooth portion 10 of the first fusible element 7i breaks. The rupture of the smooth portion 10 causes the loss of electrical continuity between said resistor 14i and the mass. The electrical resistance in the first circuit 15 measured by the electrical resistance measuring device then varies characteristically. The rupture of the first fusible element 7i results in an increase in the electrical resistance in the first electrical circuit 15.

It will be recalled that the other fuse elements 72 to 7i2 will then, in turn, break, each break causing an increase in the electrical resistance in the first electrical circuit 15. A graph representing the variation of the resistance as a function of time can be then be generated by the analysis means from the electrical resistance measurements measured in the first circuit 15. Thanks to such a graph, it is possible to determine the breaking times of each fuse element 7i to 7i2 and to deduce therefrom the time interval between each break and the time between the disturbance and each break. However, the test system according to the second embodiment does not make it possible to identify the position of the fusible element which has broken.

FIG. 7 represents a sectional view, along a plane perpendicular to the longitudinal axis X-X ’of the turbomachine, of the test system according to a third embodiment.

In the embodiment presented in FIG. 7, and in the same way as in the second embodiment, the measurement means 12i to 1212 are in contact with the fusible elements 7i to 7i2 and the upstream bearing support 5. Each element fuse is electrically connected to a first electrical circuit 15 by means of resistors 14i to 14i2. More specifically, the first electrical circuit 15 comprises a first conductive material 151 to which the resistors 14i to 14i2 are connected in parallel, each resistor being in contact with a screw head of a fuse element. In addition, the screw heads 8 of the fuse elements 7i to 7i2 are connected to a ground formed by the upstream bearing support 5. The first circuit 15 further comprises a second conductive material 152 connecting the ground to the measuring device electrical resistance.

Unlike the second embodiment, all the resistors 14i to 14i2 do not have equal electrical resistances. Indeed, in this case, a resistor 14 _n , sandwiched between two resistors 14 _n -i and 14 _n + i, does not have the same resistance as that of the two resistors 14 _n -i and 14 _n + i which are adjacent to it .

Alternatively, all the resistors 14i to 14i2 have different electrical resistances. The use of different resistors allows, in addition to the instants of rupture, to identify the position of the fusible element which has ruptured and thus to determine the order in which the fusible elements rupture. More precisely, it is possible to determine which fuse element has broken either by carrying out a calculation, by knowing the values of all the resistances of the circuit or by carrying out, before the test, measurements after having connected and disconnected each resistance alternately.

Thus, when the measuring means applies a disturbance to the rotor, a first fusible element 7i, the screw head 8 of which is in contact with a first resistor 14i, is subjected to a stress which exceeds a threshold value, the smooth portion 10 of the first fuse element 7i breaks.

In order to determine the instant of rupture of the first fuse element 7i, the electrical resistance in the first circuit 15 is measured by a first device for measuring the electrical resistance connected to the first circuit 15. The rupture of the first fuse element 7i results in an increase in electrical resistance in the first electrical circuit 15.

After the first fusible element 7i has ruptured, a second fusible element 72, in contact with a second resistor 142, adjacent to the first fusible element 7i can then rupture.

In order to determine the instant of rupture of the second fuse element 72, the electrical resistance in the first circuit 15 is measured by a second device for measuring the electrical resistance connected to the first circuit 15. The rupture of the second fuse element 72 results in an increase in electrical resistance in the first electrical circuit 15.

It is noted that the first and second devices for measuring electrical resistance can form a single device for measuring electrical resistance.

A graph representing the variation of the electrical resistance in the first circuit 15 as a function of time can then be generated by means of analysis of the electrical resistance connected to the first circuit 15. The graph obtained then makes it possible to determine the instant of rupture and the position of the fuse elements 7i and 72 having lost their connection with the first circuit 15. Finally, the graph makes it possible to determine the time interval between two breaks as well as a first delay between the disturbance applied to the rotor and the break of the first fuse element 7i and a second delay between the disturbance applied to the rotor and the rupture of the second fuse element 72.

After the first fusible element 7i and the second fusible element 72 have broken, the other fusible elements 73 to 7i2 will rupture one after the other.

FIG. 8 represents a sectional view, along a plane perpendicular to the longitudinal axis X-X ’of the turbomachine, of the test system according to a fourth embodiment.

In the fourth embodiment, unlike the second embodiment, part of the fuse elements 7i to 7i2 is electrically connected to the first electrical circuit 15 by means of a first series of resistors. Another part of the aforementioned fusible elements 7i to 7i2 is electrically connected to a second electrical circuit 18 by means of a second series of resistors.

The first electrical circuit 15 comprises a first conductive material 151 to which the first series of resistors are connected in parallel: 14i, 143,147,14s, 14g, and 14i2. Each resistor 14i, 143,147,14s, 14g, and 14i2 of the first series of resistors is in contact with a screw head 8 of a fusible element 7i, 73,77, 7s, 7g, and 7i2. In addition, the screw heads 8 are connected to a ground formed by the upstream bearing support 5. The first circuit 15 further comprises a second conductive material 152 connecting the ground to a first device for measuring electrical resistance.

The second electrical circuit 18 comprises an electrical wire 181 on which are connected in parallel the second series of resistors: 142, 144, 14s, 14e, 14ioet 14ii. Each resistor 142, 144, 14s, 14e, 14io and 14n of the second series of resistors is in contact with a screw head 8 of a fusible element 72, 73,7s, 7e, 7io and 7ii. In addition, the screw heads 8 are also connected to the ground formed by the upstream bearing support 5. The second circuit 18 is connected to the second conductive material 152 connecting the ground to a second device for measuring electrical resistance.

It is further noted that in this fourth embodiment, all of the resistors 14i to 14i2 have equal electrical resistances.

With reference to FIG. 8, the fuse elements 7i to 7i2 are distributed in the first circuit 15 and in the second circuit 18 according to a position sequence such that:

a first fuse element 7i is electrically linked to a first resistor 14i connected to the first circuit 15,

a second fuse element 72 is electrically linked to a second resistor 142 connected to the second circuit 18,

a third fuse element 73 is electrically linked to a third resistor 143 connected to the first circuit 15,

a fourth fusible element 74 is electrically linked to a fourth resistor 144 connected to the second circuit 18,

a fifth fuse element 7s is electrically linked to a fifth resistor 14s connected to the second circuit 18,

a sixth fuse element 7e is electrically linked to a sixth resistor 14e connected to the second circuit 18,

a seventh fuse element 77 is electrically linked to a seventh resistor 147 connected to the first circuit 15,

an eighth fuse element 7s is electrically linked to an eighth resistor 14e connected to the first circuit 15,

a ninth fuse element 7g is electrically linked to a ninth resistor 14g connected to the first circuit 15,

- a tenth fuse element 7io is electrically linked to a tenth resistor

1410 connected to the second circuit 18,

- an eleventh fuse element 7i 1 is electrically linked to an eleventh resistor

1411 on the second circuit 18,

- a twelfth fuse element 7i2 is in contact with a twelfth resistor 14i2 connected to the first circuit 15.

Such a position sequence of the fusible elements distributed over two electrical circuits 15 and 18 makes it possible to go back to the position of each fusible element which has broken. And this, even if all the resistors 14i to 14i2 have equal electrical resistances.

To determine the instant of rupture of each fusible element 7i to 7i2, the electrical resistance in the first circuit 15 is measured by the first measuring device connected to the first circuit 15 and the electrical resistance in the second circuit 18 is measured by the second measuring device connected to the second circuit 18.

Thus, the rupture of the first fuse element 7i results in an increase, at a time ti, in the electrical resistance in the first electrical circuit 15. It will be recalled that after the rupture of the first fuse element 7i, the other fuse elements 72 to 7i2 will then break in turn. If the break occurs at the second fuse element 72, the second measuring device connected to the second circuit 18 detects, at a time t2, an increase in the electrical resistance in the second circuit 18. After the second fuse element breaks 72, the third fuse element 73 breaks for example, which results in an increase, at a time t3, in the electrical resistance in the first circuit 15 and so on for the other fuse elements 74 to 7i2.

A first graph representing the variation of the electrical resistance in the first circuit 15 as a function of time as well as a second graph representing the variation of the electrical resistance in the second circuit 18 as a function of time can be generated by the analysis means. . The graphs obtained are, for example, in the form of a curve having stages, each stage corresponding to the rupture of a fusible element. By knowing the aforementioned sequence of position of the fusible elements and by exploiting the first and second graphs, it is then possible to deduce the instants of rupture and the positions of the fusible elements having lost their electrical connection with the first circuit 15 or with the second circuit 18. Finally, a superposition of the graphs makes it possible to determine the time interval between two breaks. In addition, it is possible to deduce the delays between the disturbance of the rotor and the rupture of the fusible elements.

The use of the test system according to the fourth embodiment improves the robustness of the measurement of the decoupling kinematics in comparison with the second and third embodiments. Indeed, during the certification tests of the turbomachine, a failure on one of the two electrical circuits can occur, the use of two circuits makes it possible to obtain information relating to the rupture of the fusible elements even in the event of failure . Indeed, carrying out certification tests on a turbomachine is costly and takes a long time to set up, it is therefore preferable for the operator to limit the number of tests by ensuring that at least one minimum information relating to the decoupling kinematics of the structuring casing 2 and the upstream bearing support 5 of the turbomachine.

FIG. 9 represents a sectional view, along a plane perpendicular to the longitudinal axis X-X ’of the turbomachine, of the test system according to a fifth embodiment.

The fifth embodiment is similar to the fourth embodiment. However, this differs from the fourth embodiment in that the resistors connected to the same circuit 15 or 18 do not have equal electrical resistances. Indeed, a resistor 14 interposed between two adjacent resistors connected to the same circuit does not have a resistance equal to that of the resistors which are adjacent to it. Furthermore, alternately, all of the resistors 14i to 14i2 have different electrical resistances.

It is recalled that the use of different resistors makes it easier to identify the fusible elements that have broken while improving the robustness of the measurement. In the fifth embodiment, the advantages of the third and the fourth embodiment are therefore combined to optimize the measurements.

Note that even if the use of two electrical circuits is particularly advantageous from a cost-robustness point of view, it is quite possible to use more than two electrical circuits or even as many electrical circuits as resistors for perform the measurements.

Furthermore, the use of the various test systems according to the invention, for measuring the decoupling kinematics of a structuring casing and of a turbomachine part, is particularly advantageous since fuses of series definition can be used. Indeed, the addition of the measurement means does not require modifying the already existing fusible elements, it is therefore not necessary to carry out a reconciliation step following the test.

The test system according to the invention allows better taking into account of the decoupling phenomenon when modeling the fusible elements.

Naturally, the test system according to the invention is not limited to equipping fusible elements for the coupling and decoupling of an upstream bearing support 5 and of a structuring casing 2. More generally, the system of test can equip any type of fusible mechanical connection element between a structuring casing linked to the engine suspensions and a turbomachine part linked to said structuring casing by bolted connections, and capable of transmitting parasitic vibrations to said structuring casing.

FIG. 10 represents a bolted connection between a structuring casing corresponding to a rear turbine casing 33 and a turbomachine part îo corresponding to an exhaust cone 22 on which a test system according to the invention can be integrated.

With reference to FIG. 10, the rear turbine casing 33 is fixed to the exhaust cone 22 by means of an internal ferrule 33a of the rear turbine casing 33. The internal ferrule 33a has, at its downstream end, a first fixing flange 41 and a second fixing flange 42. The exhaust cone 22 has, at its upstream end, a third fixing flange 51 fixed to the first and second fixing flanges 41 and 42.

A fusible element 7 allows the coupling and decoupling of the first fixing flange 41 with the third fixing flange 51. More precisely, when a disturbance is applied to the rotor mounted on the shaft 20 of the turbomachine and that the moment on the first flange 41 and the third flange 51 exceeds a threshold value, the fuse element 7 breaks so that the exhaust cone 22 then remains fixed to the rear turbine casing 33 only by the second fixing flange 42 .

In order to measure the decoupling kinematics between the first fixing flange 41 and the third fixing flange 51, the test system according to one of the embodiments described above can be used.

Claims (11)

1. Test system for measuring a decoupling kinematics between a structuring casing (2, 33) and a part (5, 22) of a turbomachine, said structuring casing (2, 33) and said part (5, 22) being coupled by a fusible element (7) along a link capable of being broken, the test system comprising: - a disturbance means adapted to apply a disturbance to a rotor supported by the structuring casing (2, 33), - a measurement means (12), in contact with the fuse element (7), measuring an electrical parameter associated with the fuse element (7) to determine a state of the fuse element (7), said measurement means (12) being dissociated from the fusible element (7), - analysis means to determine a delay between the disturbance applied by the disturbance means and a rupture of the fusible element (7). 2. Test system according to claim 1 characterized in that: the measuring means (12) comprises a piezoelectric element (13), - the electrical parameter measured is an electrical potential. 3. Test system according to claim 2, characterized in that the piezoelectric element (13) is disposed between a screw head (8) of the fusible element (7) and the part (5, 22) forming a support surface of the screw head (8). 4. Test system according to claim 2, characterized in that the piezoelectric element (13) is disposed between the structuring casing (2, 33) and the part (5, 22). 5. Test system according to claim 1 characterized in that: the measuring means (12) comprises an electrical circuit (15) to which an electrical resistance (14) is connected, - the electrical parameter is an electrical resistance. 6. Test system according to claim 5 characterized in that the electrical resistance (14) of the electrical circuit (15) is in contact with a screw head (8) of the fuse element (7) and the part (5 , 22) forming a bearing surface of the screw head (8). 7. Test system for measuring a decoupling kinematics between a structuring casing (2, 33) and a part (5, 22) of a turbomachine, said structuring casing (2, 33) and said part (5, 22) being coupled by a first fusible element (7i) and a second fusible element (72) according to claims 5 to 6, the test system comprising: - a disturbance means adapted to apply a disturbance to a rotor supported by the structuring casing (2, 33), - a first measurement means (12i), placed in contact with the first fuse element (7i), measuring an electrical parameter associated with the first fuse element (7i) to determine a state of the first fuse element (7i), said first measurement means (12i) being dissociated from the first fusible element (7i), - a second measurement means (122), placed in contact with the second fuse element (72), measuring an electrical parameter associated with the second fuse element (72) to determine a state of the second fuse element (72), said second measurement means (122) being dissociated from the second fusible element (72), - analytical means to determine: o a first delay between the disturbance applied by the disturbance means and a rupture of the first fusible element (7i), o a second delay between the disturbance by the disturbance means and a rupture of the second fusible element (72). 8. Test system according to claim 7 characterized in that: the first measuring means (12i) comprises a first electrical circuit (15) to which a first resistor (14i) is connected, - The second measuring means (12i) comprises the first electrical circuit (15) to which a second resistor (142) is connected. 9. Test system according to claim 7 characterized in that: the first measuring means (12i) comprises a first electrical circuit (15) to which a first resistor (14i) is connected, - The second measuring means (122) comprises a second electrical circuit (18) to which a second resistor (142) is connected. 10. Test system according to any one of claims 8 or 9 characterized in that the first resistance (14i) and the second resistance (142) have equal resistances. 11. Test system according to any one of claims 8 or 9 characterized in that the first resistance (14i) has a resistance different from the resistance of the second resistance (142). ³ o $