Abstract:
A test bench for an aircraft turbojet engine is provided. The test bench comprises a U-shaped configuration with a passage in the form of an elongated corridor, an inlet duct, and an outlet duct. The corridor comprises a fixing zone with a fixing arm for holding a turbojet engine during testing. The passage furthermore has an upstream shutter with vertical pivoting air guides and a downstream shutter with an inflatable balloon in a collector tube. In the event of fire, the shutters close to confine the turbojet engine in order to suffocate the fire rapidly. A method for managing a fire in a test bench with a passage is also provided. Shutters are placed in the passage, where they deploy.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit, under 35 U.S.C. §119, of BE 2015/5197 filed Mar. 30, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
       FIELD 
       [0002]    The invention concerns tests on aircraft turbojet engines. More particularly, a ground test bench for an aircraft turbojet engine. 
       BACKGROUND 
       [0003]    During the design or maintenance of a turbine engine, various tests are performed in order to validate its correct function. These tests verify the resistance during extended operating phases, by maintaining predefined speeds and forces. During these tests, a series of measurements is made to monitor key parameters. These measures can be performed both directly on the turbine engine or on its environment. 
         [0004]    In order to conduct such tests, the turbine engine is installed in a specific test bench. This is adapted to re-create flight conditions while remaining on the ground. Such a test bench has a corridor forming a passage receiving the turbine engine. Vertical ducts delimit the ends of the corridor in order to form an inlet and an outlet, receiving and then injecting the air flow propelled by the turbine engine. Devices reduce the noise nuisance which is inherent in the operation of the turbine engine and propagated via the ducts. 
         [0005]    Document EP 1 860 416 A2 discloses a test bench allowing determination of a turbine engine thrust. The test bench has a U-shaped configuration, i.e. it has an inlet duct, an outlet duct, the ducts being connected by a horizontal corridor. Upstream, a first mesh supports the pressure sensors, then a mesh blocks debris at the inlet to the intake mouth of the engine  4 . The corridor is partitioned downstream and is completed by a detuner. 
         [0006]    During a test, an oil or fuel pipe can rupture. There is then a risk of an engine fire breaking out. Such an event can damage the test bench and in particular its sensors. Naturally, the turbine engine itself can suffer severe damage. The consequences of such an incident lead to major damage which then requires repair, further delaying the possibility of reusing the turbine engine. This scenario becomes paradoxical in the context of an overhaul, since a test is intended to authorize flight of a turbine engine rather than extend delays. Heavy financial losses result from such immobilization on the ground. 
       SUMMARY 
       [0007]    An object of the invention is to solve at least one of the problems posed by the prior art. More precisely, an object of the invention is to reduce the impact of a fire breaking out in the test bench. An object of the invention is also to suffocate as quickly as possible a fire which breaks out in a test bench for a turbine engine. 
         [0008]    It will be understood that an object of the invention is a test bench comprising a flow corridor intended to receive an engine, in particular a turbine engine, the bench being fitted with at least one and in various instances two shutters. One is placed upstream of the zone intended to receive the turbine engine, the other being placed downstream of the zone. 
         [0009]    An object of the invention is also a test bench for an engine, in particular a turbojet or turboprop engine, wherein the test bench comprises an inlet, an outlet, and a passage allowing a circulation of air between the inlet and the outlet. The passage is intended to receive the engine during testing, wherein the passage comprises at least one movable shutter able to cut off the circulation of air between the inlet and the outlet so as to be able to suffocate a fire occurring in the passage at the engine. 
         [0010]    According to various advantageous embodiments of the invention, the shutter comprises a movable part which is delimited by the passage and which is able to seal the passage. 
         [0011]    According to various advantageous embodiments of the invention, the shutter comprises portions which are movable relative to each other during the opening and/or closing movements of the shutter, the portions coming into contact with each other and/or moving apart from each other. 
         [0012]    According to various advantageous embodiments of the invention, the shutter comprises at least one movable portion which is configured to pivot between the open position and the closed position of the shutter. 
         [0013]    According to an advantageous embodiment of the invention, the passage comprises a corridor intended to receive the engine, and/or vertical ducts, in various instances the shutter being situated in the corridor. 
         [0014]    According to various advantageous embodiments of the invention, the shutter comprises articulated air guides, in the open position the guides are parallel to a same plane so as to be able to guide the circulation of air parallel to the passage. The aspect “parallel to the passage” can be understood as parallel to the walls—for instance vertical—of the passage. 
         [0015]    According to various advantageous embodiments of the invention, the shutter comprises articulated air guides, in the open position the guides are parallel to the main elongation of the passage, and/or in the closed position the guides are inclined relative to the main elongation. The main elongation can be the main straight line inside the passage. 
         [0016]    According to various advantageous embodiments of the invention, the guides are chamfered so they can be in plane-to-plane contact with the adjacent guide when the shutter is closed. 
         [0017]    According to various advantageous embodiments of the invention, the shutter comprises an inflatable element, for example a balloon. 
         [0018]    According to various advantageous embodiments of the invention, it comprises a gas supply means, such as a pump and/or a reservoir, for inflating the inflatable element. 
         [0019]    According to various advantageous embodiments of the invention, the passage comprises a collector tube able to collect an air flow driven by the engine, for example for a detuner, the inflatable element being placed at the level of the tube so as to be able to seal the tube. 
         [0020]    According to various advantageous embodiments of the invention, the collector tube comprises a tubular portion configured to protrude towards the engine, in various instances the bench comprises a partition across the passage, the tubular portion protruding relative to the partition. 
         [0021]    According to various advantageous embodiments of the invention, the shutter comprises an elastic envelope, the modulus of elasticity of the envelope being between 1 MPa and 100 MPa, e.g., between 2 MPa and 40 MPa, in some cases between 5 MPa and 20 MPa. 
         [0022]    According to various advantageous embodiments of the invention, the shutter is a first shutter, the passage also comprising a second shutter able to cut off the circulation of air between the inlet and the outlet of the passage, the shutters being configured to define an enclosure around the engine so as to be able to suffocate a fire occurring in the passage. 
         [0023]    According to various advantageous embodiments of the invention, the passage comprises a fixing zone for the engine to be tested, the zone being placed between the two shutters, e.g., the fixing zone comprises a fixing arm such as a descending post. 
         [0024]    According to various advantageous embodiments of the invention, the passage comprises a main direction for the circulation of air from the inlet towards the outlet, in various instances the main direction follows the central axis of the passage. 
         [0025]    According to various advantageous embodiments of the invention, the shutter is movable between an open position and a closed position. 
         [0026]    According to various advantageous embodiments of the invention, the passage comprises concrete walls, in particular concrete reinforced with a metal grid, and in some cases foundations. 
         [0027]    According to various advantageous embodiments of the invention, the passage and/or the corridor measures more than 10 m in length, for example more than 20 m, e.g., more than 70 m. The length of the corridor can be measured in a straight line. 
         [0028]    According to various advantageous embodiments of the invention, the passage has a clear cross section greater than 4 m2, for example greater than 25 m2, e.g., greater than 50 m2, in some cases greater than 100 m2. 
         [0029]    According to various advantageous embodiments of the invention, the test bench comprises a fixing arm, in some cases a bracket or suspension post, intended for fixing the engine. 
         [0030]    According to various advantageous embodiments of the invention, the engine is able to exert a thrust greater than or equal to 20 kN, for example greater than or equal to 80 kN, e.g., greater than or equal to 200 kN, in some cases greater than or equal to 500 kN. The fixing arm is designed to receive the corresponding forces. 
         [0031]    According to various advantageous embodiments of the invention, the shutter is movable between a retracted configuration and a deployed configuration in which it cuts the circulation of air in the passage between the inlet and the outlet. 
         [0032]    An object of the invention is also a method for managing a fire in a test bench for an engine, in particular for a turbojet or turboprop engine, the test bench comprising a passage in which the engine is fixed in order to be tested, distinguished in that the test bench comprises a shutter able to close the passage, and in that in the event of fire, the shutter is deployed from the passage. 
         [0033]    According to an advantageous embodiment of the invention, in the normal operating state, in particular in the absence of fire, the shutter is placed in the passage and has an open configuration allowing a circulation of air via the passage. 
         [0034]    According to an advantageous embodiment of the invention, the shutter comprises an inflatable element which is deployed in the passage by inflation in the event of fire, and where applicable the inflatable element is continuously supplied with inflation fluid. 
         [0035]    According to an advantageous embodiment of the invention, in the event of fire, the shutter is filled with a neutral gas. 
         [0036]    In general, the advantageous embodiments of each object of the invention are also applicable to the other objects of the invention. As far as possible, each object and each advantageous embodiment can be combined. 
         [0037]    The presence of the portion of the shutter which pivots allows an improvement in compactness and limits its impact on the flow circulating in the test bench. In the open position, each shutter is partially or in various instances fully housed in the passage, in particular the corridor, which allows it to seal this even more quickly. 
         [0038]    The presence of a guide allows the use of elements necessary for guiding flow. They are immersed therein during normal operation. Consequently, their change of configuration is more rapid. Pivoting through a fraction of a turn is sufficient to close the passage. Five seconds are sufficient for a shutter to be formed. 
         [0039]    An inflatable element benefits from a low inertia. Its flexible envelope can adapt to the surfaces of the passage with which it cooperates. The flexible material intrinsically offers a true seal inside the passage. Inflation can take place in a few seconds, increasing the safety of the bench. The two shutters can be operated automatically. The adhesion of the inflatable element due to friction allows its resistance to the thrust of the flow driven by the turbojet engine. This resistance is applied during the auto-rotation time of the turbojet engine, as well as resistance to temperatures of the order of 300° C. 
         [0040]    Two shutters allow tight confinement of a reduced zone so as to accelerate the suffocation of a fire which breaks out therein. They are placed close to the turbojet engine, which limits the quantity of oxygen remaining in the resulting enclosure. This further accelerates suffocation of the fire. 
     
    
     
       DRAWINGS 
         [0041]      FIG. 1  shows a test bench receiving an engine to be tested, in accordance with various embodiments of the invention. 
           [0042]      FIG. 2  is a diagram of an upstream shutter in the open position, in accordance with various embodiments of the invention. 
           [0043]      FIG. 3  is a diagram of the upstream shutter in the closed position, in response to a fire, in accordance with various embodiments of the invention. 
           [0044]      FIG. 4  is a diagram of a downstream shutter in the open position, in accordance with various embodiments of the invention. 
           [0045]      FIG. 5  is a diagram of a downstream shutter in the closed position, in response to a fire, in accordance with various embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]      FIG. 1  shows in a simplified form a test bench  2  for an engine  4 , for example a test bench  2  for a turbine engine  4 , for example an aircraft turbojet engine  4 . 
         [0047]    The test bench  2  forms an infrastructure or construction. It comprises a passage  6  with an inlet  8  and an outlet  10 . The passage  6  can comprise an essentially elongated corridor  12 . A length of the corridor can be greater than 10 m, for example greater than 30 m, for example greater than 50 m. The length of the corridor  12  allows the straight circulation of an air flow  14  or air circulation  14 , limiting turbulence. In order to limit the flow resistance, in particular the entry of an air flow  14  into the turbojet engine  4 , the corridor  12  can have a clear cross-section that is greater than or equal to 20 m 2 , for example greater than or equal to 50 m 2 . The clear cross-section or free cross-section can be measured upstream of a fixing zone  16  intended to receive the turbojet engine  4 . The clear cross-section can be observed over at least one-quarter of the length of the corridor  12 , for instance over the majority thereof. 
         [0048]    The corridor  12  can have the fixing zone  16  that can be fitted with a fixing arm  18  where the turbojet engine  4  is mounted. The arm  18  can extend vertically from the ceiling of the corridor  12 , in the manner of a column or post. The arm  18  allows the turbojet engine  4  to be mounted with an offset, and be centred in the middle of the corridor  12 . The centring is vertical and horizontal. 
         [0049]    The corridor  12  can be delimited by vertical ducts  20  and  22  at the inlet  8  and outlet  10 . The ducts  20  and  22  allow a vertical air intake and outlet at a height. To reduce sound nuisance, the ducts  20  and  22  can comprise sound baffles  24  or acoustic plates  24  to absorb the sound waves. Further devices  26  can be present at the inlet  8  and outlet  10 , to prevent flow inversions which would disrupt the test conditions. The U-shaped configuration presented here is not essential; other configurations, for example without ducts, can be considered. A chamber alone can form the passage  6 . 
         [0050]    At the junction between the upstream duct  20  and the corridor  12 , the bench is equipped with a series of deflection plates  28 . The deflection plates  28  allow the air descending from the inlet duct  20  to be deflected in a horizontal direction. The deflection plates  28  extend horizontally and across the entire corridor  12 . The deflection plates  28  have curved profiles. At the inlet to the corridor  12 , the bench  2  optionally has a mesh  30  to intercept debris liable to disrupt the test and damage the turbojet engine. 
         [0051]    Downstream of the turbojet engine  4 , the bench  2  comprises a collector tube  32  collecting the air flow  14  propelled by the turbojet engine, or engine&#39;s exhaust gases. The mouth of the collector tube  32  can form a funnel or cone downstream. The collector tube  32  helps absorb the noise created by the test. The collector tube  32  is arranged horizontally and at its outlet comprises a diffuser  34  in the outlet duct  22 . 
         [0052]    The collector tube  32  can be held in the bench via at least one partition  36 , in various instance two partitions  36 . These partitions  36  extend vertically and transversely in the corridor  12 . One partition  36  can form a separation between the corridor  12  and the outlet duct  22 . The partitions form sealed separations which allows the flow  14  from the turbojet engine  4  to be contained. 
         [0053]    In order to contain a fire which can occur at the turbojet engine  4 , the test bench is equipped with an upstream shutter  38  and/or a downstream shutter  40 . The downstream shutter  40  is exemplarily shown here in the closed position with dotted lines. Two shutters  38  and  40  are shown, in various embodiments, only one shutter  38  or  40  is necessary in the sense of the invention, since a sprinkler can also be used in combination to extinguish a fire  42 . 
         [0054]      FIG. 2  is a view from above of the upstream shutter  38  in the open position. A portion of the corridor  12  and the turbojet engine  4  are shown. The bench  2  is functioning in normal test conditions in the usual fashion. 
         [0055]    The upstream shutter  38  comprises air guides  44  to guide the air flow  14  axially relative to the axis  46  of the turbojet engine  4 . These air guides  44  are articulated such that they can pivot around vertical axes. Alternatively, they can be horizontal and be articulated pivotingly around horizontal axes. 
         [0056]    The air guides  44  are spaced laterally and are exemplarily shown in  FIG. 2  being parallel to each other. The air guides  44  form a row. The air guides  44  are also parallel to a same plane, which allows the guidance or orientation of air flow towards the turbojet engine. The guides  44  allow limitation and, in various instances, suppression of the turbulence which can persist in the flow because of its speed.  FIGS. 2 and 3  exemplarily illustrate six guides  44  are, however, it is envisioned that any other number of guides  44  could be implemented, such as fifteen or thirty. 
         [0057]      FIG. 3  is a view from above of the upstream shutter  38  in the closed position. A portion of the corridor  12  and the turbojet engine  4  are shown. The upstream shutter  38  is in the closed position because of the start of the fire  42 , which corresponds to an unusual or abnormal operation of the bench. 
         [0058]    In order to pivot into the closed position, the guides  44  pivot towards each other until they meet. The guides  44  turn through a turn fraction of less than one-eighth of a turn, in various instances less than one-sixteenth of a turn. The guides  44  come into contact along their upstream and downstream edges, in various instances over their entire height. Motors and linkages actuate the guides  44 . 
         [0059]    When closed, the guides  44  describe a zigzag or sawtooth pattern. The guides  44  are divided into two sets of guides  44 , positioned alternately. The sets of guides  44  turn in opposite directions, e.g., one set turns clockwise and the other set turns anticlockwise. The guides  44  of one set become parallel to a first plane, the guides  44  of the other set become parallel to a second plane which is inclined relative to the first plane. 
         [0060]    Their upstream and downstream contacts can be essentially tight, as is the contact between the lateral guides  44  and the walls  48  of the corridor  12 . To optimize this aspect, in various embodiments the guides are advantageously chamfered in order to form plane-to-plane contacts with adjacent chamfers. The chamfers can have joints. Also, the chamfers improve the aerodynamics. 
         [0061]    In some cases, the deflection plates  28  of the bench  2  are articulated and can form a shutter by turning until they come into contact, for example tightly, with each other. The sound baffles can also be articulated so as to form shutters. 
         [0062]      FIG. 4  depicts an enlargement of the downstream shutter  40  in the open position which allows the circulation of a flow. A downstream part of the turbojet engine  4  and the collector tube  32  are shown. 
         [0063]    The downstream shutter  40  is placed in the corridor  12  at the level of the tube  32 , downstream of the turbojet engine  4 . The downstream shutter  40  can be an inflatable element  40  such as a bladder or a balloon  40 . In the open position or configuration, it can be housed in a niche  50 , for example in the upper part of the tube  32 . This niche  50  allows the downstream shutter  40  to be held retracted relative to the air flow  14  in the tube  32 , so as not to decelerate the flow. 
         [0064]      FIG. 5  depicts an enlargement of the downstream shutter  40  in the closed position following the start of a fire  42 . A portion of the corridor  12  and the turbojet engine  4  are shown. 
         [0065]    The downstream shutter  40  is deployed across the clear cross-section of the tube  32 . It can comprise a flexible envelope  52 , allowing deformation between a retracted configuration and the deployed configuration. The envelope  52  can be elastic and expand on inflation of the shutter  40 . The envelope  52  can comprise a silicone elastomer and/or polyurethane and/or rubber envelope. These materials can be reinforced mechanically and/or thermally. 
         [0066]    In the inflated configuration, the shutter  40  can be spherical or have any other form corresponding to that of the tube  32 . The shutter  40  is adapted to seal the tube  32  tightly, in order to prevent the renewal of air around the turbojet engine  4 . 
         [0067]    The inflation of the shutter  40  can be achieved using a neutral gas. Such a gas can contribute to suffocating the flames in the case of leakage. The gas is pressurised in order to retain the sealing form of the shutter  40 . For inflation, the bench  2  can comprise gas supply means  54  with conduits, a pump or a reservoir such as a cylinder. The gas supply means  54  are advantageously placed outside the tube  32 , in some cases outside the corridor  12 . 
         [0068]    The tube  32  can have a square profile, and not be exclusively circular. The upstream shutter  40  can block the passage in a few seconds, which allows very quick action. It does not require an operation of displacement or equipment release. A simple manual control can provoke inflation, as can a fire sensor connected to the supply means  54 . 
         [0069]    When the fire  42  is under control, each shutter is retracted. The guides can resume an open, parallel configuration. The inflatable element  40  can be deflated such that it again allows passage through the tube  32 . Suction or actuation can allow retraction of the shutter  40 , for example into its niche  50 . The guides  44  can also resume an arrangement parallel to the corridor axis  46 .