Exhaust duct of a turbine test bench comprising a double tube

Abstract

The invention relates to an exhaust duct of a gas-turbine test bench, comprising an outer tube (10) extending along a longitudinal axis (X1) with an inlet (11) capable of recovering the exhaust gases moved by a gas turbine (90). This exhaust duct comprises at least one inner tube (20) which extends along a longitudinal axis (X2) with an inlet (21) and is located inside the outer tube (10) such that, in operation, an inner gas flow (F20) circulates in the at least one inner tube (20) and an outer gas flow (F10), separated from the inner flow (F20), circulates in the outer tube (10) outside the at least one inner tube (20).

Description

Description Title: Exhaust duct of a turbine test bench with a double tube

[0001] The present invention relates to a gas turbine test bench. More specifically, the invention relates to an exhaust duct for such a test bench, comprising an external tube extending along a longitudinal axis with an inlet for recovering the gases displaced by a gas turbine and an outlet. In particular, the invention relates to a turbomachine test bench.

[0002] Such a test bench is described in document EP 3021102. With reference to Figure 7, which represents the prior art, the test bench comprises, from upstream to downstream (in the normal direction of airflow), an inlet chimney 181, a test room 182, an exhaust duct of a turbine test bench, and an exhaust chimney 183. Air enters the test room 182 through the vertical inlet chimney 181, which is open to the outside at its inlet. The test room 182 includes a turbomachine 190 which is mounted on a thrust balance 191. Downstream of the tested turbomachine 190, there is an exhaust duct of a turbine test bench which includes a tube 110 which is intended to receive at its inlet 111 (upstream end) the exhaust gases which escape from the turbomachine 190 during its test.This tube 110 is fitted at its outlet 112 (downstream end) with a burst basket 113, which is a cylinder closed at its downstream end by a concave lid and perforated on its lateral wall with holes. The exhaust gases exit the burst basket through these holes and rise in the exhaust stack 183 before exiting into the atmosphere.

[0003] During operation of the turbomachine, three airflows can be distinguished circulating in test room 182: - the primary flow (PF), which passes through the combustion chamber (HP (High Pressure) core) of the turbomachine 190 and participates in combustion. This primary flow PF is therefore loaded at the outlet with CO2 but also with water, Sox, Nox and other particles; - the secondary flow (FS), which is compressed by the turbomachine 190 fan and which generates most of the thrust; - the induced airflow (induced flow Fl), which is drawn in by the depression at the outlet of the turbomachine 190. Indeed, the engine flow, the sum of the primary flow FP and the secondary flow FS, upon entering the tube 110 of the exhaust duct, carries with it, by jet horn effect, an induced flow which circulates in the test room 182 without passing through the turbomachine 190. These different flows are illustrated in Figure 8 by arrows. Figure 8 is a longitudinal view of the turbomachine 190 and the upstream portion of tube 110 in Figure 7. For clarity, the thrust balance 191 is not shown. All these flows circulate in tube 110 of the exhaust duct of a turbine test bench.

[0004] Due to combustion in the turbomachine 190, the above-mentioned flows, which mix and circulate in the exhaust duct of a turbine test bench, contain carbon dioxide (CO2), which is released into the atmosphere at the outlet of the exhaust stack 183. This release of carbon dioxide is undesirable. It is possible to place a carbon dioxide filtration device 170 in the exhaust stack 183. However, the concentration of carbon dioxide in the flow circulating in the exhaust stack 183 is low, making such a filtration device ineffective. Description of the invention

[0005] The present invention aims to remedy these drawbacks.

[0006] The invention aims to provide a device that helps to make the capture of carbon dioxide CO2, carbon particles and other pollutants generated by a gas turbine test bench as efficient as possible.

[0007] This goal is achieved by the fact that the exhaust duct of the gas turbine test bench includes at least one inner tube extending along a longitudinal axis with an inlet and an outlet and which is located inside the outer tube such that in operation an internal flow of gas circulates in the at least one inner tube and an external flow of gas separate from the internal flow circulates in the outer tube outside the at least one inner tube.

[0008] Thanks to these arrangements, the gas flow (which in this case circulates within the inner tube) is primarily composed of the primary combustion stream. Consequently, this gas flow has a maximized concentration of carbon dioxide, carbonaceous particles, and pollutants, which facilitates its removal and reduces the size of the gas removal system. Furthermore, this gas flow has a higher temperature than a flow circulating in an outer tube without an inner tube. The heat from this gas flow can therefore be recovered more efficiently.

[0009] Advantageously, the inner tube is unique and coaxial with the outer tube.

[0010] Advantageously the inner tube is unique and the longitudinal axis of the inner tube is located in a vertical plane above the longitudinal axis of the outer tube and parallel to this longitudinal axis.

[0011] Advantageously the inlet of at least one inner tube is located downstream of the inlet of the outer tube by a longitudinal distance.

[0012] Advantageously, at least one inner tube is fixed to the outer tube by a fixing mechanism.

[0013] Thus, the assembly of the exhaust duct is simplified.

[0014] Advantageously the outer tube has an outlet and at least one inner tube has an outlet which is located downstream of the outlet of the outer tube.

[0015] Advantageously the outer tube has an outlet and at least one inner tube has an outlet, and the at least one inner tube includes, upstream of its outlet and downstream of said outlet of the outer tube, a diffuser which is a conduit whose cross-section increases from upstream to downstream so as to reduce the flow velocity of the gases which pass through this diffuser.

[0016] The invention also relates to an assembly consisting of an exhaust duct of a turbine test bench according to the invention and a pollution control system located downstream of the outlet of at least one internal tube and capable of receiving the internal flow.

[0017] The invention also relates to a gas turbine test bench comprising a building having an air inlet chimney at one end of the building and a gas exhaust chimney at the other end of the building, a test room extending between the inlet chimney and the exhaust chimney, a thrust balance located in the test room and adapted to receive the gas turbine for testing, an exhaust duct of a gas turbine test bench according to the invention, this exhaust duct being located downstream of the gas turbine when it is mounted on the thrust balance and being positioned relative to the gas turbine such that the central axis of the gas turbine passes through at least one inner tube and the outer tube is adapted to receive the gas flow displaced by the gas turbine,and the test bench further includes a pollution control system located downstream of the outlet of at least one internal tube and capable of receiving the internal flow circulating in the at least one internal tube.

[0018] Advantageously the maximum dimension of at least one internal tube is greater than or equal to the equivalent diameter of the ejection nozzle of the gas turbine.

[0019] The invention will be better understood and its advantages will become more apparent upon reading the following detailed description of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings in which:

[0020] [Fig. 1] Figure 1 is a perspective view of a turbomachine test bench according to a first embodiment of the invention.

[0021] [Fig. 2] Figure 2 is a perspective view of a turbomachine test bench according to a variant of the first embodiment of the invention illustrated in Figure 1.

[0022] [Fig. 3] Figure 3 is a side view of the upstream part of an exhaust duct of a turbine test bench according to the invention.

[0023] [Fig. 4] Figure 4 is a side view of the upstream part of an exhaust duct of a turbine test bench according to a variant of the invention.

[0024] [Fig. 5] Figure 5 is a perspective view of the upstream part of an exhaust duct according to the invention which shows the fixing mechanism between the inner and outer tubes.

[0025] [Fig. 6] Figure 6 is a perspective view of a turbomachine test bench according to a second embodiment of the invention.

[0026] [Fig. 7] Figure 7, already described, is a perspective view of a turbomachine test bench according to the prior art.

[0027] [Fig. 8] Figure 8, already described, is a side view of the upstream part of the turbomachine test bench in Figure 7. Detailed description of the invention

[0028] In the description below, the terms "upstream" and "downstream" are defined with respect to the normal direction of gas and air flow in the test bench, in the gas turbine and in the exhaust duct of a turbine test bench during normal operation of that turbine.

[0029] The invention is described below in the case where the gas turbine 90 is a turbomachine, but applies to any gas turbine where the displaced gas must be cleaned.

[0030] Figure 1 shows a turbomachine test bench 90 comprising an exhaust duct of a turbine test bench (of this turbomachine) according to the invention. This test bench 80 comprises a building 88 which includes, from upstream to downstream (in the normal direction of airflow during operation of the turbomachine 90), an inlet stack 81, a test room 82 and a (first) exhaust stack 83. Air enters the test room 82 through the vertical inlet stack 81 which is open to the outside at its inlet. The test room 82 includes a turbomachine 90 which is mounted on a thrust balance 91. Downstream of the tested turbomachine 90, there is an exhaust duct of a turbine test bench which includes a tube 10 which extends along a longitudinal axis X1 and which is intended to receive at its inlet 11 (upstream end) the exhaust gases which escape from the turbomachine 90 during its test.The longitudinal axis X1 is substantially the longitudinal axis along which the turbomachine 90 extends. The tube 10 is fitted at its outlet 12 (downstream end) with a basket. The burst 13 is a cylinder closed downstream by a concave lid (convex as seen by the gas flow) and perforated on its lateral wall with holes. The gas flow F10, which circulates in the tube 10 outside the inner tube 20 (see description below and in Figure 3), exits the burst basket 13 through these holes and rises in the exhaust stack 83 before exiting into the atmosphere. This tube 10 is called the outer tube 10, as opposed to the inner tube 20, which is described below.

[0031] The exhaust duct of a turbine test bench includes an inner tube 20 which extends along a longitudinal axis X2 with an inlet 21 and an outlet 22 and which is located inside the outer tube 10 and in the same direction.

[0032] During operation of the turbomachine 90, three airflows can be distinguished circulating in the test room 82: - the primary flow (PF), which passes through the combustion chamber (HP (High Pressure) core) of the turbomachine 90 and participates in combustion. This primary flow (PF) is therefore laden with CO2 at the outlet, but also with water, SOx, NOx and other particles. - the secondary flow (FS), which is compressed by the turbomachine 90's fan and generates most of the thrust. This secondary flow FS initially circulates around the primary flow FP. - the induced airflow (Fl), which is drawn in by the vacuum at the outlet of the turbomachine 90. Indeed, the engine flow, the sum of the primary flow FP and the secondary flow FS, upon entering the external tube 10, entails by jet horn effect a so-called "induced" flow which circulates in the test room 82 without passing through the turbomachine 90. This induced flow Fl initially circulates around the secondary flow FS.

[0033] During operation, the primary flow FP, secondary flow FS, and induced flow Fl enter and then circulate within the outer tube 10, as illustrated by arrows in Figure 3. The term "gas displaced by the turbomachine" refers to the gases and air that constitute all of these primary flow FP, secondary flow FS, and induced flow Fl. Figure 3 is a longitudinal view of the turbomachine 90 and the upstream portion of the outer tube 10 and the inner tube 20 of Figure 1. For clarity, the thrust balance 91 is not shown.

[0034] In operation, an internal flow F20 of gas circulates inside the inner tube 20 and an external flow F10 of gas separate from the internal flow F20 circulates in the outer tube 10 outside the inner tube 20.

[0035] The outer tube 10 and the inner tube 20 are coaxial, as illustrated in Figures 1 and 2 (as well as in Figures 3, 5, and 6). The longitudinal axes X1 and X2 are therefore coincident. The outer tube 10 and the inner tube 20 are concentric.

[0036] Thanks to its central position within the outer tube 10, the inner tube 20 preferentially receives the most central gas flow, that is, the flow closest to the longitudinal axis X1. Thus, the internal flow F20 consists of the majority, if not almost all, of the primary flow FP, and a portion of the secondary flow FS. The external flow F10 consists of the remainder of the secondary flow FS and almost all of the induced flow Fl. For example, the external flow F10 consists of the majority of the secondary flow FS and all of the induced flow Fl.

[0037] Tests carried out by the inventors show that up to 92% of the primary flow FP can be captured in the inner tube 20. Since the primary flow FP is by far the one of the three flows (FP, FS, Fl) that is most heavily loaded with carbon dioxide, carbon particles and other pollutants, the invention makes it possible to increase the concentration of carbon dioxide, carbon particles and other pollutants in the flow treated by the filtration system (pollution control system) 70 located downstream of the inner tube 10 (see below), compared to the flow that circulates in an exhaust pipe without an inner tube 20.

[0038] Conversely, the F10 gas flow circulating in tube 10 outside the inner tube 20, exiting the burst basket 13 and then rising in the exhaust stack 83, contains very few pollutants (even less than the flow circulating in the exhaust duct without the inner tube 20). Therefore, this F10 gas flow can be allowed to exit through the extraction stack 83 without filtering or treating it.

[0039] Alternatively, to the configuration where the outer tube 10 and the inner tube 20 are coaxial, the longitudinal axis X2 of the inner tube 20 is located in a vertical plane above the longitudinal axis X1 of the outer tube 10 and parallel to this longitudinal axis X1. In other words, the inner tube 20 is translated in a vertical plane (containing the longitudinal axis X1) relative to the position where the outer tube 10 and the inner tube 20 are concentric. This configuration is illustrated in Figure 4. This configuration has the advantage that more combustion gases are captured in the inner tube 20 since the natural ejection trajectory of the gases from the turbomachine 90 can be upwards.

[0040] The longitudinal central axis of the turbomachine 90 extends in the same direction as the longitudinal axis X1 and the longitudinal axis X2. In all cases, the turbomachine 90 is positioned relative to the inner tube 20 such that this central axis of the turbomachine 90 passes through the inner tube 20 (and extends in the same direction as the inner tube 20).

[0041] In all cases, the maximum dimension D2 of the inner tube 20 is strictly less than the maximum dimension D1 of the outer tube 10. For example, the maximum dimension D2 is less than or equal to half the maximum dimension D1. If both the inner tube 20 and the outer tube 10 have a circular cross-section (their cross-section is a circle), as illustrated in all the figures, the maximum dimensions D1 and D2 are the diameters of these circles. The diameters D1 and D2 are shown in Figure 3.

[0042] Alternatively, the inner tube 20 and the outer tube 10 each have an ellipse as their cross-section. Alternatively, the inner tube 20 and the outer tube 10 each have a polygon as their cross-section, for example a square or a rectangle.

[0043] According to one variant (not shown), the internal tube 20 is divided transversely, that is to say by a wall which extends along the longitudinal axis X2, over all or part of its length.

[0044] According to one variant (not shown), the outer tube 10 is divided transversely into two half-tubes by a wall which extends along its entire length along the longitudinal axis X1. In this variant, the inner tube 20 is for example formed by one of these half-tubes, or for example is housed in one of these half-tubes.

[0045] According to one variant, the maximum dimension D2 of the inner tube 20 is greater than or equal to the diameter of the primary flow FP which is emitted by the combustion chamber of the turbomachine 90, measured immediately at the outlet of this combustion chamber. In other words, the maximum dimension D2 is greater than or equal to the equivalent diameter of the turbomachine 90 ejection nozzle. Thus, all or almost all of the primary flow FP passes through the inner tube 20.

[0046] As illustrated in figure 1, the inlet 21 of the inner tube 20 is located downstream of the inlet 11 of the outer tube 10 by a longitudinal distance LT. This longitudinal distance LT is therefore non-zero.

[0047] For example, the longitudinal distance LT between the inlets (11, 21) is less than half the length L of the outer tube 10 (see Figure 1). For example, the longitudinal distance LT is preferably greater than 0.8 times the maximum dimension D1 of the outer tube 10.

[0048] Alternatively, the inlet 21 of the inner tube 20 and the inlet 11 of the outer tube 10 are located in the same transverse plane (with respect to the longitudinal axis X1).

[0049] The inner tube 20 is fixed to the outer tube 10 by a fastening mechanism 30. For example, this fastening mechanism 30 consists of a plurality of radial fins 31 that are regularly distributed along the circumference of the inner tube 20 in the space between the inner tube 20 and the outer tube 10. Each fin 31 extends longitudinally in the direction of the longitudinal axis X2. For example, the number of fins is four, as illustrated in Figure 5 in the case where the inner tube 20 and the outer tube 10 are coaxial. Alternatively, the fastening mechanism consists of a plurality of radial rods that are distributed in the space between the inner tube 20 and the outer tube 10 along the inner tube 20 in several transverse planes, and regularly distributed, in each transverse plane, along the circumference of the inner tube 20.

[0050] The outlet 22 of the inner tube 20 is located downstream of the outlet 12 of the outer tube 10. Thus the inner tube 20 extends downstream of the outer tube 10 with a constant cross-section, as illustrated in figure 1.

[0051] Advantageously, the inner tube 20 is equipped at its outlet 22 with a burst basket 23, which is a cylinder closed downstream by a concave lid and perforated on its lateral wall with holes. The internal flow F20 exits the burst basket 23 through these holes and rises in a second exhaust chimney 84 which encompasses the outlet 22 and the bursting basket 23. The second exhaust chimney 84 is part of building 88, as illustrated in figure 1 (or in figure 2 which is a variant of the embodiment of figure 1, described below).

[0052] The invention also relates to an assembly comprising an exhaust duct of a turbine test bench as described above, and a pollution control system 70 located downstream of the outlet 22 of the inner tube 20 and adapted to receive the internal flow F20 circulating in the inner tube 20. The pollution control system 70 includes a pollution control filter 71. The pollution control system 70 is located in the second exhaust stack 84, for example directly above the spark gap basket 23, as illustrated in Figure 1 (or Figure 2). This pollution control system 70, by virtue of its filter, is adapted to capture carbon dioxide (CO2), carbonaceous particles, and other polluting particles present in the internal flow F20, such that, downstream of the pollution control system 70, the gas in the internal flow F20 is treated by this pollution control filter 71.This pollution control process is made more efficient thanks to the higher density of carbon dioxide CO2, carbonaceous particles and other polluting particles which are in the internal flow F20 (this density is higher than if the internal tube 20 were absent).

[0053] According to a first embodiment, described above with reference to Figure 1, the pollution control system 70 is part of the test bench 80 and the building 88.

[0054] In this first embodiment, according to a variant, the inner tube 20 includes, upstream of its outlet 22 and downstream of the outlet 12 of the outer tube 10, a diffuser 24 which is a conduit, for example a conical conduit, whose cross-section increases from upstream to downstream. Thus, the flow velocity of the gases passing through this diffuser 24 is reduced, which makes it possible to increase the quantity of gas captured and the pressure drop available for the pollution control system 70 positioned downstream of the burst basket 23. This situation is illustrated in Figure 2.

[0055] According to a second embodiment, the pollution control system 70 is part of the test bench 80 and is not part of the building 88. The pollution control system 70 then comprises a pollution control building 72, separate from the building 88, which contains the pollution control filter 71, and the outlet of the internal tube 20 is located in this pollution control building 72 such that the internal flow F20 passes through this filter 71.

[0056] In this second embodiment, according to a first variant (not illustrated), the pollution control system 70 is located away from the building 88 and remains in the main direction of the building (from the inlet chimney 81 towards the first exhaust chimney 83). Thus, the inner tube 20 extends along the longitudinal axis X2 outside the building 88 to this pollution control system 70. The outlet 22 of the inner tube 20 is either equipped with a burst basket 23, or without this burst basket 23 (in which case the outlet 22 is equipped with at least one orifice through which the gas exits into the pollution control building 72).

[0057] In this second embodiment, according to a second variant illustrated in Figure 6, the pollution control system 70 is offset from the building 88. Thus, the internal tube 20 extends in a curved fashion (away from the longitudinal axis X2), outside the building 88, to this pollution control system 70. The outlet 22 of the internal tube 20 is either equipped with a bursting basket 23, or without this bursting basket 23. Figure 6 illustrates the case where the outlet of the internal tube 20 is equipped with a bursting basket 23.

[0058] An exhaust duct of a turbine test bench 90 according to the invention allows for a gas flow at a higher temperature than in an exhaust duct according to the prior art. Indeed, the internal flow F20 circulating in the internal duct 20 is essentially composed of the primary flow FP, which exits directly from the combustion chamber of the turbomachine 90 and is therefore at a higher temperature than the secondary flow FS and the induced flow Fl. Thus, the internal flow F20 has a higher temperature than the external flow F10 circulating in the external tube 10 outside the internal tube 20, and a higher temperature than a flow circulating in the external tube without an internal tube in the prior art. Advantageously, the internal duct 20 is thermally connected to a heat exchanger (not shown) which is capable of recovering this heat for a given application.This heat exchanger operates more efficiently because the internal flow F20 is at a higher temperature. Tests conducted by the inventors show that in the inner tube 20, it is possible to... increase the temperature of the recovered flow by 50°C (compared to an exhaust duct without an internal tube 20).

[0059] The invention also relates to a gas turbine test bench 80 90 with a turbine test bench exhaust duct and a pollution control system 70 as described above.

[0060] Thus, the gas turbine 90 test bench 80 comprises a building 88 which has an air inlet chimney 81 at one end of the building and at least one gas exhaust chimney (83, 84) at a second end of the building, a test room 82 extending between the inlet chimney 81 and the exhaust chimney (83, 84), a thrust balance 91 located in the test room 82 and suitable for receiving the turbomachine 90 for testing, an exhaust duct of a turbine test bench which is located downstream of the turbomachine 90 when it is mounted on the thrust balance 91 and which is positioned relative to the turbomachine such that the central axis of the turbomachine passes through the inner tube 20 of the exhaust duct and the outer tube 10 is suitable for receiving the gas flow displaced by the turbomachine.The test bench 80 further includes a pollution control system 70 located downstream of the outlet 22 of the inner tube 20 and capable of receiving the internal flow F20 circulating within the inner tube 20. In one configuration, the building 88 comprises a single exhaust stack 83, and the pollution control system 70 is located outside this building 88, either attached to it, offset along its axis, or offset from its main direction. In another configuration, the building comprises a (first) exhaust stack 83 and a second exhaust stack 84, and the pollution control system 70 is located within this second exhaust stack 84.

[0061] The invention has been described above in the configuration where the exhaust duct comprises a single internal tube 20. Alternatively, in another configuration, the exhaust duct comprises two or more parallel internal tubes 20 located inside the external tube 10. In a first variant of this configuration, these internal tubes 20 are arranged side by side, that is, each internal tube 20 has a longitudinal axis X2 that is parallel to and distinct from the longitudinal axes X2 of the other internal tubes 20. By For example, these internal tubes 20 all have the same diameter. In a second variant of this configuration, these internal tubes 20 are concentric. In other words, these internal tubes 20 are coaxial, meaning that the longitudinal axes X2 of all these tubes coincide. The diameters D2 of any two internal tubes 20 are then necessarily different.

[0062] The invention has been described above in the case where the turbomachine is a twin-spool turbofan. The invention also applies to a test bench for any type of turbomachine such as a turbojet, a triple-spool turbofan, a turboshaft, or a military engine.

Claims

Claims

1. Exhaust duct of a gas turbine test bench comprising an outer tube (10) extending along a longitudinal axis (X1) with an inlet (11) capable of recovering the gases displaced by a gas turbine (90), said exhaust duct being characterized in that it comprises at least one inner tube (20) extending along a longitudinal axis (X2) with an inlet (21) and which is located inside said outer tube (10) such that in operation an internal flow (F20) of gas circulates in said at least one inner tube (20) and an external flow (F10) of gas, separated from said internal flow (F20), circulates in said outer tube (10) outside said at least one inner tube (20).

2. An exhaust duct of a gas turbine test bench according to claim 1 such that said inner tube (20) is single and is coaxial with said outer tube (10).

3. Exhaust duct of a gas turbine test bench according to claim 1 such that said inner tube (20) is single and the longitudinal axis (X2) of said inner tube (20) is located in a vertical plane above the longitudinal axis (X1) of said outer tube (10) and parallel to this longitudinal axis (X1).

4. Exhaust duct of a gas turbine test bench according to any one of claims 1 to 3 such that said inlet (21) of the at least one inner tube (20) is located downstream of said inlet (11) of the outer tube (10) by a longitudinal distance (LT).

5. An exhaust duct of a gas turbine test bench according to any one of claims 1 to 4 such that said at least one inner tube (20) is fixed to the outer tube (10) by a fixing mechanism (30).

6. An exhaust duct of a gas turbine test bench according to any one of claims 1 to 5 such that said outer tube (10) has an outlet (12) and said at least one inner tube (20) has an outlet (22) which is located downstream of the outlet (12) of said outer tube (10).

7. An exhaust duct of a gas turbine test bench according to any one of claims 1 to 6 such that said outer tube (10) comprises an outlet (12) and said at least one internal tube (20) comprises an outlet (22), and such that said at least one internal tube (20) comprises, upstream of its outlet (22) and downstream of said outlet (12) of the external tube (10), a diffuser (24) which is a conduit whose cross-section increases from upstream to downstream so as to reduce the flow rate of the gases which pass through this diffuser (24).

8. Assembly consisting of an exhaust duct of a gas turbine test bench according to any one of the preceding claims and a pollution control system (70) located downstream of said outlet (22) of said at least one internal tube (20) and capable of receiving said internal flow (F20).

9. A gas turbine (90) test bench (80) characterized in that it comprises a building (88) which has an air inlet chimney (81) at a first end of the building (88) and a gas exhaust chimney (83, 84) at a second end of the building (88), a test room (82) extending between the inlet chimney (81) and the exhaust chimney (83, 84), a thrust balance (91) located in said test room (82) and adapted to receive said gas turbine (90) for testing, an exhaust duct of a gas turbine test bench according to any one of claims 1 to 7,said exhaust duct being located downstream of said gas turbine (90) when mounted on said thrust balance (91) and being positioned relative to said gas turbine (90) such that the central axis of said gas turbine (90) passes through said at least one inner tube (20) and said outer tube (10) is adapted to receive the gas flow displaced by said gas turbine (90), and said test bench (80) further comprises a pollution control system (70) which is located downstream of the outlet (22) of said at least one inner tube (20) and which is adapted to receive said internal flow (F20) which circulates in said at least one inner tube (20).,

10. Test bench (80) for a gas turbine (90) according to claim 9 such that the maximum dimension (D2) of said at least one internal tube (20) is greater than or equal to the equivalent diameter of the exhaust nozzle of said gas turbine (90).

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