Flexible retention assembly for turbomachine rotating part burst test bench

Abstract

The invention relates to a flexible retention assembly (4) for a test bench (1) for bursting a rotating part of a turbomachine to be tested (9), said test bench (1) comprising: a hollow cylindrical wall (10); a drive shaft (2) on which said rotating part to be tested (9) is intended to be fixed; an annular furnace (7) formed around said drive shaft (2); means for retaining fragments from said rotating part to be tested (9) comprising: a rigid retention assembly (3); said flexible retention assembly (4), said flexible retention assembly (4) comprising at least one flexible retention element (40) of hollow cylindrical shape extending along a longitudinal axis (X), characterized in that said flexible retention assembly (4) further comprises means for cooling said at least one flexible retention element (40). Figure 2.

Description

Title of the invention: Flexible retention assembly for a turbomachine rotating part burst test bench. Field of the invention

[0001] The present invention relates to the field of aeronautics, and more specifically, to test benches for aircraft turbomachinery.

[0002] More particularly, the invention relates to a test bench for bursting of a rotating part of a turbomachine. Prior art

[0003] In aeronautics, it is known to implement test benches in order to control the risks of bursting of rotating parts, and more particularly of rotating parts of turbomachinery.

[0004] Such test benches conventionally comprise a hollow cylindrical wall defining an internal test tank in which is provided a drive shaft mounted movable in rotation around the longitudinal axis of the tank and on which is intended to be fixed the rotating part to be tested.

[0005] The tests of these rotating parts are carried out both at ambient temperature and at temperatures up to more than 700°C. To this end, the test benches also conventionally include an annular furnace formed around the drive shaft and intended to surround and heat the rotating part to be tested during high-temperature tests.

[0006] Rotating part burst test benches must be able to ensure the retention of fragments of the rotating part that might escape during the bursting of that rotating part. Conventionally, this retention is ensured by two separate elements provided inside the tank: - an internal retention element, called flexible, which is the first element to be impacted by the fragments escaping during the bursting and whose function is therefore to ensure the retention of these fragments without damaging them so as not to distort a subsequent expert assessment; - an external retention element, called hard, which is placed opposite or even in contact with an external surface of the internal element and whose function is to ensure the safety of a user or an installation around the test bench in the event of failure to retain fragments by the internal element.

[0007] It should be noted that by "flexible" and "hard" we mean the ability to deform upon impact with fragments escaping during bursting.

[0008] In other words, the soft retention element deforms more easily upon impact with fragments than the hard retention element so as to retain these fragments without damaging them, while the hard retention element deforms less easily upon impact with fragments than the soft retention element so as to ensure the safety of a user or an installation around the test bench.

[0009] A flexible retention element generally takes the form of a hollow cylinder or a circular ring with a predefined thickness depending on the required or desired retention capacity of this flexible retention element. It may, in particular, be made of aluminum to provide satisfactory deformation capacity while maintaining retention qualities suitable for its intended use.

[0010] Nowadays, the materials developed for rotating parts of turbomachinery are increasingly resistant, and consequently, the speeds and energies required for a rotating part to break are increasingly greater. Therefore, the retention capacity of a test bench must be increased accordingly.

[0011] In addition to thickness, the temperature of the flexible retention elements plays an essential role in the debris retention capacity, with a high temperature decreasing the fragment retention capacity.

[0012] However, the increase in the thickness of current flexible retention elements is limited by the problem of their integration into the test bench and, as a result, the retention capacity for a given test bench may not be sufficient to meet the requirements of a test, especially if the tests are carried out at high temperature and therefore with a lower retention capacity.

[0013] There is therefore a need to provide a solution to improve such test benches in order to meet the retention capacity requirements of a turbomachine rotating part burst test bench. Description of the invention

[0014] The invention aims to remedy at least in part the aforementioned drawbacks relating to prior art techniques.

[0015] To this end, the invention relates to a flexible retention assembly for a test bench for bursting a rotating part of a turbomachine to be tested, said test bench comprising: - a hollow cylindrical wall defining an internal test tank having a first hollow cylindrical volume VI extending along a longitudinal axis L; - a drive shaft mounted to rotate freely around said longitudinal axis L and on which said rotating part to be tested is intended to be fixed; - an annular oven formed around said drive shaft and intended to surround and heat said rotating part to be tested during the tests, - means for retaining fragments originating from said rotating part to be tested, said means for retaining fragments comprising: - a rigid retention assembly intended to be housed in said first hollow internal volume VI and comprising at least one rigid retention element of hollow cylindrical shape defining a second hollow cylindrical internal volume V2 intended to extend along said longitudinal axis L; - said flexible retention assembly, intended to be housed in said second hollow internal volume V2,

[0016] said flexible retention assembly comprising at least one flexible retention element of hollow cylindrical shape extending along a longitudinal axis X and defining a third hollow cylindrical interior volume V3 intended to house said annular furnace.

[0017] According to the invention, said flexible retention assembly further includes means for cooling said at least one flexible retention element.

[0018] Thus, the solution proposes a new and inventive approach that makes it possible to resolve at least in part some of the drawbacks of the prior art.

[0019] Indeed, by implementing cooling means for at least one flexible retention element, heating of the entire flexible retention assembly is limited, and it thus retains its mechanical retention properties. This makes it possible to increase the retention capacity of a test bench without increasing, or only slightly increasing, the thickness of current flexible retention elements, and therefore to solve the space problem within the test bench tank.

[0020] According to a particular aspect of at least one embodiment of the invention, said cooling means for said at least one flexible retention element comprise a heat transfer fluid circulation circuit flowing through said at least one flexible retention element between an inlet manifold and an outlet manifold.

[0021] According to a particular aspect of at least one embodiment of the invention, said at least one flexible retention element is formed by stacking along said longitudinal axis X a plurality of rows of unit elements, said heat transfer fluid circulation circuit circulating through each of said unit elements.

[0022] In this way, it is possible to limit mechanical weaknesses by not aligning the ends of the unitary elements of composite material in columns.

[0023] According to a particular aspect of at least one embodiment of the invention, each unit element having an upper face and a lower face opposite said upper face and comprising: - a first portion of conduit formed between a first orifice on the said lower face and opening at a first pin extending projecting from the said upper face, and - a second portion of conduit, parallel to the said first portion of conduit, and formed between a second orifice at the level of the said lower face and opening at the level of a second pin extending in projection from the said upper face,

[0024] said first and second orifice having a form complementary to said first and second pins so that said plurality of conduits circulating through each of said unitary elements is formed by stacking said unitary elements at the location of said first and second orifice and of the first and second pins.

[0025] This makes it easier to assemble the unit elements and also ensures the correct assembly of the fluid circulation circuit.

[0026] According to a particular aspect of at least one embodiment of the invention, said unit elements have a portion-of-a-cylinder shape, said plurality of rows of unit elements being stacked in a staggered pattern, such that, for three successive rows of unit elements stacked in a staggered pattern: - a first portion of conduit of a given unit element of a second row is connected to a second portion of conduit of a first unit element of the two unit elements of a first row opposite said given unit element and is connected to a second portion of conduit of a first unit element of the two unit elements of a third row opposite said given unit element, a first orifice of said given unit element of said second row being connected to a second pin of said first unit element of the two unit elements of said third row opposite said given unit element, a first pin of said given unit element of said second row being connected to a second orifice of said first unit element of the two unit elements of said first row opposite said given unit element, - a second portion of duct of said given unit element of said second row is connected to a first portion of duct of a second unit element of the two unit elements of said first row opposite said given unit element and is connected to a first portion of duct of a second unit element of the two unit elements of said third row opposite said given unit element, a second orifice of said given unit element of said second row being connected to a first pawn of said second unit element of the two unit elements of said third row opposite said given unit element, a second pawn of said given unit element of said second row being connected to a first orifice of said second unit element of the two unit elements of said first row opposite said given unit element.

[0027] According to a particular aspect of at least one embodiment of the invention, each of said unit elements has sealing means provided on an external surface of each of said first and second pins.

[0028] This ensures sealing during the assembly of the unit elements of the retention element and also of the fluid circulation circuit.

[0029] According to a particular aspect of at least one embodiment of the invention, said sealing means comprise an O-ring formed in a housing hollowed out from said outer surface of each of said first and second pins and intended to fit into said first and second orifice of unit elements opposite each other on a higher row when said unit elements are stacked.

[0030] According to a particular aspect of at least one embodiment of the invention, said at least one flexible retention element is formed of a plurality of tubes extending along said longitudinal axis X and radially distributed in several rows, said heat transfer fluid circulating through said tubes between said inlet manifold and said outlet manifold.

[0031] According to a particular aspect of at least one embodiment of the invention, said tubes are made of aluminum.

[0032] According to a particular aspect of at least one embodiment of the invention, said rows of tubes are radially separated from each other by aluminum sheets.

[0033] According to a particular aspect of at least one embodiment of the invention, said at least one flexible retention element is radially divided into a plurality of sectors.

[0034] According to a particular aspect of at least one embodiment of the invention, said at least one flexible retention element has a thickness contained between an internal radially cylinder and an external radially cylinder of between 50mm and 200mm.

[0035] The invention also relates to a test bench comprising: - a hollow cylindrical wall defining an internal test tank having a first hollow cylindrical volume VI extending along a longitudinal axis L; - a drive shaft mounted to rotate freely around said longitudinal axis L and on which said rotating part to be tested is intended to be fixed; - an annular oven formed around said drive shaft and intended to surround and heat said rotating part to be tested during the tests, - means for retaining fragments originating from said rotating part to be tested, said means for retaining fragments comprising: - a rigid retention assembly intended to be housed in said first hollow internal volume VI and comprising at least one rigid retention element of hollow cylindrical shape defining a second hollow cylindrical internal volume V2 intended to extend along said longitudinal axis L; - a flexible retention assembly according to one of the aforementioned embodiments, intended to be housed in said second hollow internal volume V2 so that said longitudinal axis X of said at least one flexible retention element is coincident with said longitudinal axis L of said first hollow cylindrical volume VI, said drive shaft being mounted in rotation around said longitudinal axis L in said third hollow cylindrical internal volume V3 housing said annular furnace.

[0036] According to a particular aspect of at least one embodiment of the invention, said cooling means for said at least one flexible retention element are connected to an external cooling source.

[0037] According to a particular aspect of at least one embodiment of the invention, said annular furnace is chosen from a resistive furnace or an induction furnace. Presentation of the figures

[0038] The invention, as well as the various advantages it presents, will be more easily understood in the light of the following description of illustrative and non-limiting embodiments thereof, and of the accompanying drawings among which: [Fig.1] is a schematic cross-sectional view of a test bench according to one embodiment of the invention; [Fig.2] is a schematic top cross-sectional view of a test bench according to the embodiment of [Fig.1]; [Fig.3] is a schematic perspective view of a retention element according to one embodiment of the invention; [Fig.4] is a partial schematic lateral section view of a retention assembly according to a first embodiment of the invention; [Fig.5] is a detailed view of part of [Fig.4]; [Fig.6] is an exploded schematic view of part of [Fig.5]; [Fig.7] is an exploded schematic view of part of [Fig.6]; [Fig. 8] is a partial schematic top view of a retention assembly according to a second embodiment of the invention, and [Fig.9] is a schematic side view of the retention assembly according to a second embodiment of the invention.

[0039] Detailed description of an embodiment of the invention

[0040] It should be noted that the invention applies to any type of test bench for performing burst tests on rotating parts. More particularly, the invention is presented in relation to the field of aeronautics, and more specifically to burst tests of rotating parts of turbomachinery.

[0041] These rotating parts of a turbomachine can, for example, be turbine or compressor discs which can be fitted with blades.

[0042] A first embodiment of the invention is now presented in relation to figures 1 to 7.

[0043] As illustrated, the test bench 1 comprises a hollow cylindrical wall 10 defining an internal test tank extending along a longitudinal axis L.

[0044] This internal test tank has a first hollow cylindrical volume V1 which defines the volume available both for carrying out the tests and for implementing the fragment retention assemblies from the rotating part.

[0045] The hollow cylindrical wall can for example be made of metal capable of withstanding impacts with fragments that could escape from the retention assemblies.

[0046] The test bench also includes a drive shaft 2 mounted movable in rotation around the longitudinal axis L and on which the rotating part to be tested 9 is intended to be fixed. In this way, during burst tests, the part to be tested rotates around the longitudinal axis of the cylindrical tank so as to be substantially centered on the inner tank.

[0047] Since some tests also need to be carried out at a higher temperature than ambient temperature, the test bench also includes an annular furnace 7 arranged around the drive shaft 2 and configured to surround the rotating part to be tested so as to raise its temperature.

[0048] This annular furnace 7 can more particularly be chosen from a resistive furnace or an induction furnace so as to be able to reach temperatures of 700°C.

[0049] In order to be able to ensure the retention of fragments of the rotating part which would escape during the bursting of this rotating part, said test bench 1 further includes means for retaining fragments from the rotating part to be tested 9.

[0050] These means for retaining fragments include: - a rigid retention assembly 3 intended to be housed in the first hollow internal volume VI and comprising at least one rigid retention element 30 of hollow cylindrical shape defining a second hollow cylindrical interior volume V2 intended to extend along the longitudinal axis L; - a flexible retention assembly 4 intended to be housed in the second hollow internal volume V2 and comprising at least one flexible retention element 40 of hollow cylindrical shape defining a third hollow cylindrical internal volume V3 intended to extend along the longitudinal axis L so that the drive shaft 2 is mounted to rotate around the longitudinal axis L in the third hollow cylindrical internal volume V3 and that this third hollow cylindrical internal volume V3 houses the annular furnace 7.

[0051] It is understood that a hard retention assembly can be formed by a stacking of several hard retention elements 30 along the longitudinal axis L so as to form a hard retention assembly having a hollow cylindrical shape.

[0052] Similarly, it is understood that a flexible retention assembly can be formed by stacking several flexible retention elements 40 along the longitudinal axis L so as to form a flexible retention assembly having a hollow cylindrical shape.

[0053] In particular, in relation to [Fig.3], a flexible retention element 40 is presented. As can be seen, this flexible retention element 40 is of hollow cylindrical shape and extends along a longitudinal axis X. When this flexible retention element is positioned inside the inner test tank, and more particularly inside the hollow cylindrical inner volume V2, the longitudinal axis X coincides with the longitudinal axis L of the inner tank.

[0054] This flexible retention element 40 can be radially divided into a plurality of sectors 4000 in order to facilitate its placement in the internal test tank and also to facilitate its removal once the tests have been carried out.

[0055] Such a flexible retention element 40 can, depending on the circumstances and the tests to be carried out, have a thickness contained between an internal radially cylinder and an external radially cylinder of between 50mm and 200mm.

[0056] The term radially internal cylinder refers to the radially internal limit of this retention element which defines the third hollow cylindrical internal volume V3. Furthermore, the term radially external cylinder refers to the radially external limit of this flexible retention element, which is therefore opposite the rigid retention assembly.

[0057] According to the invention, in order to limit heating of the flexible retention assembly and thus maintain its mechanical retention properties, the flexible retention assembly 4 further comprises means for cooling said at least one flexible retention element 40.

[0058] Figures 4 to 7 illustrate in particular the implementation of such a flexible retention assembly 4.

[0059] In the illustrated embodiment, and as seen in particular in [Fig.4], the cooling means for at least one flexible retention element 40 include a heat transfer fluid circulation circuit 5.

[0060] This heat transfer fluid circulation circuit is implemented so that the fluid circulates through at least one flexible retention element 40 between an inlet manifold 5A and an outlet manifold 5B.

[0061] These cooling means for at least one flexible retention element 40 are here connected to an external cooling source 8.

[0062] This external cooling source can in particular be a heat pump which allows the fluid to be recirculated in a closed circuit.

[0063] More particularly, in this embodiment, each flexible retention element 40 is formed by stacking along the longitudinal axis X a plurality of unit elements 400.

[0064] As a result, the heat transfer fluid circulation circuit flows through each of the unit elements 400 as illustrated in figures 4 to 6.

[0065] To do this, each of the unit elements 400 carries portions of conduits so that after assembly, this can form a heat transfer fluid circulation circuit.

[0066] Each unit element has an upper face 500 and a lower face 501 opposite the upper face 500.

[0067] Each unit element more particularly comprises a first portion of conduit 51 formed between a first orifice 510 formed at the level of the lower face 501 and opening at the level of a first pin 511 extending in projection from the upper face 500, and a second portion of conduit 52, parallel to the first portion of conduit 51, and formed between a second orifice 520 formed at the level of the lower face 501 and opening at the level of a second pin 521 extending in projection from the upper face 500.

[0068] Furthermore, and to ensure the assembly of the unit elements 400, the first orifice 510 and the second orifice 520 respectively have a shape complementary to the first pin 511 and the second pin 521.

[0069] Thus, the plurality of conduits circulating through each of the unit elements is formed by stacking the unit elements 400, and therefore by assembling the first portion of conduit 51 and second portion of conduit 52, at the location of the first orifice 510 and the second orifice 520 and the first pin 511 and second pin 521.

[0070] In order to facilitate assembly, the first portion of conduit 51 and the second portion of conduit 52 are identical here.

[0071] As a result, the first orifice 510 and the second orifice 520 are identical, as are the first pin 511 and the second pin 521.

[0072] As illustrated in this embodiment, the stacking along the longitudinal axis X of a plurality of rows of unit elements 400 is carried out in a staggered pattern.

[0073] More particularly, the unit elements 400 have a portion-cylinder shape, so as to allow the plurality of unit elements of two superimposed retention elements 40 in contact to be stacked in a staggered pattern with respect to each other.

[0074] The fact that the plurality of rows of unit elements are stacked in a staggered pattern ensures that the ends of each unit element are not positioned in line with the ends of an opposite unit element in a row of contact. This limits mechanical weaknesses by preventing the alignment of the ends of the composite material unit elements, and therefore the joint lines between two successive unit elements.

[0075] Thus, for a flexible retention assembly 4 comprising several flexible retention elements 40, for two successive flexible retention elements 40, a row of unit elements of a first of the two successive flexible retention elements 40 in contact with a row of unit elements of a second of the two successive flexible retention elements 40 is arranged in a staggered pattern with the row of unit elements of the second of the two successive flexible retention elements 40.

[0076] Thus, the stacking is carried out as follows, with reference to Figures 5 and 6. For three successive rows RI, R2, R3 of unit elements 400 stacked in a staggered pattern: - a first portion of conduit 51 of a given unit element 400N of a second row R2 is connected to a second portion of conduit 52 of a first unit element 400A of the two unit elements 400A, 400B of a first row R1 opposite said given unit element 400N and is connected to a second portion of conduit 52 of a first unit element 400C of the two unit elements 400C, 400D of a third row R3 opposite said given unit element 400N, a first orifice 510 of said given unit element 400N of said second row R2 being connected to a second pin 521 of said first unit element 400C of the two unit elements 400C, 400D of said third row R3 opposite said given unit element 400N, a first pin 511 of said unit element given 400N of said second row R2 being connected to a second orifice 520 of said first unit element 400A of the two unit elements 400A,400B of said first row RI opposite said given unit element 400N, , - a second portion of conduit 52 of said given unit element 400N of said second row R2 is connected to a first portion of conduit 51 of a second unit element 400B of the two unit elements 400A, 400B of said first row RI opposite said given unit element 400N and is connected to a first portion of conduit 51 of a second unit element 400D of the two unit elements 400C, 400D of said third row R3 opposite said given unit element 400N, a second orifice 520 of said given unit element 400N of said second row R2 being connected to a first pin 511 of said second unit element 400D of the two unit elements 400C, 400D of said third row R3 opposite said given unit element 400N, a second pin 521 of said given unit element 400N of said second row R2 being connected to a first orifice 510 of said second unit element 400B of the two unit elements 400A, 400B of said first row RI opposite said given unit element 400N.

[0077] In order to maintain the tightness of the heat transfer fluid circulation circuit, each of the unit elements 400 has sealing means. Indeed, it is at the point of assembly of the unit elements with each other that sealing problems could arise in the heat transfer fluid circulation circuit.

[0078] More particularly, in this embodiment and as illustrated in [Fig.7], the sealing means are provided here on an external surface of each of the first pin 511 and second pins 521 of each of the unit elements 400.

[0079] These sealing means here include an O-ring 53 provided in a housing 54 cut from the outer surface of each of the first pin 511 and second pins 521 of each of the unit elements 400.

[0080] These O-rings are intended to fit into the first orifice 510 and second orifice 520 of unit elements opposite each other on a higher row when the unit elements 400 are stacked.

[0081] More specifically, a sealing gasket 53 formed in a housing 54 cut from the outer surface of the first pin 511 of the given unit element 400N of the second row R2 is inserted into a second orifice 520 of the first unit element 400A of the two unit elements 400A, 400B of the first row RI opposite the given unit element 400N. For its part, a sealing gasket 53 formed in a housing 54 cut from the outer surface of the second pin 521 of the given unit element 400N of the second row R2 is inserted into a first orifice 510 of the second unit element 400B of the two unit elements 400A, 400B of the first row RI opposite the given unit element 400N.

[0082] A second embodiment of the invention is now presented in relation to Figures 8 and 9.

[0083] As illustrated, in this second embodiment, and instead of a set of unit elements, at least one flexible retention element 40' is formed of a plurality of 400' tubes extending along the longitudinal axis X and radially distributed in several rows.

[0084] Horn visible on [Fig.8], the rows of tubes 400' are radially separated from each other by sheets, which here are aluminum sheets 401.

[0085] In this way, said heat transfer fluid can circulate through the tubes 400' between said inlet manifold 5A and outlet manifold 5B so as to cool the tubes.

[0086] In this second embodiment, the tubes are made from aluminium so as to ensure sufficient retention capacity.

Claims

Demands

1. Flexible retention assembly (4) for test bench (1) for bursting of rotating part of turbomachine to be tested (9), said test bench (1) comprising: - a hollow cylindrical wall (10) defining an internal test tank having a first hollow cylindrical volume (VI) extending along a longitudinal axis (L); - a drive shaft (2) mounted to rotate freely about said longitudinal axis (L) and on which said rotating part to be tested (9) is intended to be fixed;- an annular oven (7) provided around said drive shaft (2) and intended to surround and heat said rotating part to be tested (9) during the tests, - means for retaining fragments from said rotating part to be tested (9), said means for retaining fragments comprising: - a hard retention assembly (3) intended to be housed in said first hollow internal volume (VI) and comprising at least one hard retention element (30) of hollow cylindrical shape defining a second hollow cylindrical internal volume (V2) intended to extend along said longitudinal axis (L);- said flexible retention assembly (4), intended to be housed in said second hollow internal volume (V2), said flexible retention assembly (4) comprising at least one flexible retention element (40) of hollow cylindrical shape extending along a longitudinal axis (X) and defining a third hollow cylindrical internal volume (V3) intended to house said annular furnace (7), characterized in that said flexible retention assembly (4) further comprises means for cooling said at least one flexible retention element (40).

2. A flexible retention assembly (4) according to claim 1, characterized in that said cooling means for said at least one flexible retention element (40) comprise a heat transfer fluid circulation circuit (5) flowing through said at least one flexible retention element (40). less a flexible retention element (40) between an inlet manifold (5A) and an outlet manifold (5B).

3. Flexible retention assembly (4) according to the preceding claim, characterized in that said at least one flexible retention element (40) is formed by stacking along said longitudinal axis (X) a plurality of rows of unit elements (400), said heat transfer fluid circulation circuit flowing through each of said unit elements (400).

4. A flexible retention assembly (4) according to the preceding claim, characterized in that each unit element (400) has an upper face (500) and a lower face (501) opposite said upper face (500) and comprises: - a first portion of conduit (51) formed between a first orifice (510) formed at said lower face (501) and opening at a first pin (511) projecting from said upper face (500), and - a second portion of conduit (52), parallel to said first portion of conduit (51), and formed between a second orifice (520) formed at said lower face (501) and opening at a second pin (521) projecting from said upper face (500), said first and second orifices (510, 520) having a shape complementary to said first and second pins (511,521) so that said plurality of conduits circulating through each of said unit elements (400) is formed by stacking said unit elements (400) at said first and second orifices (510, 520) and first and second pins (511, 521).

5. A flexible retention assembly (4) according to the preceding claim, characterized in that said unit elements (400) have a cylindrical shape, said plurality of rows of unit elements (400) being stacked in a staggered pattern, such that, for three successive rows (RI, R2, R3) of unit elements (400) stacked in a staggered pattern: - a first conduit portion (51) of a given unit element (400N) of a second row (R2) is connected to a second conduit portion (52) of a first unit element (400A) of the two unit elements (400A, 400B) of a first row (R3) opposite said given unit element (400N) and is connected to a second conduit portion (52) of a first unit element (400C) of the two unit elements (400C, 400D) of a third row (R3) opposite said given unit element (400N), a first orifice (510) of said given unit element (400N) of said second row (R2) being connected to a second pin (521) of said first unit element (400C) of the two unit elements (400C, 400D) of said third row (R3) opposite said given unit element (400N), a first pin (511) of said given unit element (400N) of said second row (R2) being connected to a second orifice (520) of said first unit element (400A) of the two unit elements (400A, 400B) of said first row (RI) opposite said given unit element (400N),a second conduit portion (52) of said given unit element (400N) of said second row (R2) is connected to a first conduit portion (51) of a second unit element (400B) of the two unit elements (400A, 400B) of said first row (R3) opposite said given unit element (400N) and is connected to a first conduit portion (51) of a second unit element (400D) of the two unit elements (400C, 400D) of said third row (R3) opposite said given unit element (400N), a second orifice (520) of said given unit element (400N) of said second row (R2) being connected to a first pin (511) of said second unit element (400D) of the two unit elements (400C, 400D) of said third row (R3) opposite said unit unit given (400N),a second pin (521) of said given unit element (400N) of said second row (R2) being connected to a first orifice (510) of said second unit element (400B) of the two unit elements (400A, 400B) of said, first row (RI) opposite said given unit element (400N).

6. Flexible retention assembly (4) according to any one of claims 4 or 5, characterized in that each of said unit elements (400) has sealing means provided on an external surface of each of said first and second pins (511, 521).

7. Flexible retention assembly (4) according to the preceding claim, characterized in that said sealing means comprise an O-ring (53) provided in a housing (54) cut from said outer surface of each of said first and second pins (511, 521) and intended to fit into said first and second orifice (510, 520) of opposite unit element on a higher row when said unit elements (400) are stacked.

8. Flexible retention assembly (4) according to claim 2, characterized in that said at least one flexible retention element (40') is formed of a plurality of tubes (400') extending along said longitudinal axis (X) and radially distributed in several rows, said heat transfer fluid circulating through said tubes (400') between said inlet manifold (5A) and said outlet manifold (5B).

9. Flexible retention assembly (4) according to the preceding claim, characterized in that said tubes are made of aluminum.

10. Flexible retention assembly (4) according to any one of claims 8 or 9, characterized in that said rows of tubes (400') are radially separated from each other by aluminum sheets (401).

11. Test bench (1) comprising: - a hollow cylindrical wall defining an internal test chamber (10) having a first hollow cylindrical volume (VI) extending along a longitudinal axis (L); - a drive shaft (2) mounted to rotate about said longitudinal axis (L) and on which said rotating part to be tested (9) is intended to be fixed; - an annular furnace (7) formed around said drive shaft (2) and intended to surround and heat said rotating part to be tested (9) during the tests,

12.

13. - means for retaining fragments originating from said rotating part to be tested (9), said means for retaining fragments comprising: - a hard retention assembly (3) intended to be housed in said first hollow internal volume (VI) and comprising at least one hard retention element (30) of hollow cylindrical shape defining a second hollow cylindrical internal volume (V2) intended to extend along said longitudinal axis (L); - a flexible retention assembly (4) according to any one of claims 1 to 10, intended to be housed in said second hollow internal volume (V2) so that said longitudinal axis (X) of said at least one flexible retention element (40) is coincident with said longitudinal axis (L) of said first hollow cylindrical volume (VI), said drive shaft (2) being mounted in rotation about said longitudinal axis (L) in said third hollow cylindrical internal volume (V3) housing said annular furnace (7). Test bench (1) according to the preceding claim, characterized in that said cooling means for said at least one flexible retention element (40) are connected to an external cooling source (8). Test bench (1) according to one of claims 11 or 12, characterized in that said annular furnace (7) is selected from a resistive furnace or an induction furnace.

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