FR3017711A1 - GAS COLLECTOR FOR TURBOKARKER TEST BENCHES - Google Patents

Description

Field of the Invention The field of the present invention is that of ground test stands for turbojet engines.

State of the art The turbojets require for their development or for the verification of their performance at the end of maintenance, a passage on a test bench on the ground. These tests are conducted in a closed facility to avoid environmental damage, including noise. These installations conventionally comprise, as will be explained in detail with reference to FIGS. 1 and 2, an air supply, a room in which the turbojet engine is arranged, and means for evacuating the flue gases. The means for evacuating the burned gases generally comprise an entity commonly named by the skilled person "detuner" (for detuner in French) which is located immediately downstream of the turbojet engine and whose function is to recover the burnt gases from the turbojet engine. and channel them. In the following, the detuner will be named gas collector.

The air passing through the turbojet is sucked into the test bench room. The speed of the exhaust gas causes a circulation of air in the room, said induced air, which passes around the turbojet engine and which is driven by the effect of horn, by the gases leaving the exhaust nozzle of the turbojet engine. Furthermore, one of the challenges of closed test benches is to ensure a good evacuation of the gas from the turbojet engine to avoid any re-ingestion of hot gases by the turbojet engine, that is to say a phenomenon called recirculation that disrupts the operation of the turbojet engine and therefore distorts the measurements that are made. In practice, it is considered that the quality of the evacuation can be quantified by the induced air flow, a strong induced air flow reducing the risk of re-ingestion. The gas collector captures the gases leaving the turbojet and the induced air which forms a ring circulation around the jet of the nozzle. These gases are evacuated, out of the test room, through the gas collector, in a room, called exhaust room, before being released into the atmosphere. The gas manifold typically comprises a frustoconical horn disposed facing the exhaust nozzle of the turbojet, which is continued by a cylindrical pipe and which eventually terminates in a conical outlet nozzle. The gases at the outlet of this gas manifold are generally taken up by a second pipe, called a mixing tube, where the hot gases from the turbojet engine and the fresh air induced in the test room mix. The gas collector is movable in translation along its axis of symmetry, which makes it possible, more or less away from the exhaust nozzle of the turbojet engine, to optimize the recovery of the gases. The diameter of the outlet nozzle of the exhaust manifold is adapted to a type of turbojet engine. Indeed, its output section is sized to be able to evacuate the flow of the mixture of hot gases from the turbojet engine and fresh air from the induced flow of the test room. The flow rate of a more powerful turbojet engine means a higher flow rate of hot gases. If the section of the outlet nozzle of the exhaust manifold remains constant between the small and the large turbojet engine, this implies that the air flow induced with the large turbojet engine will be less important than with the small turbojet, which may result in an air velocity induced in the test room too low resulting in a risk of re-ingestion of hot gases by the turbojet engine or a risk of vortex formation in the test room. This then requires a larger output section for the gas manifold with a large turbojet, compared with a small turbojet engine. Generally the outlet section of the gas manifold is optimized for the largest turbojet engine to be tested in the test bench. When it is then desired to test a turbojet engine of smaller size, it is necessary to reduce the output section and for this a solution consists, for example, in adding a frustoconical part to the existing part. In some cases this may be insufficient and the only solution is then replacing the gas header in place with a smaller gas manifold.

SUMMARY OF THE INVENTION The purpose of the present invention is therefore to propose a gas manifold for a reactor test bench that is adaptable to different sizes of turbojet engine, without the need to replace the manifold or to add additional devices to it. . For this purpose, the subject of the invention is a gas manifold for a turbojet engine test bench comprising an inlet bell and a cylindrical part contiguous downstream of said bell, characterized in that it furthermore comprises downstream of the cylindrical part, a variable section outlet nozzle. This variability makes it possible to install turbojets of different power in the bank and to be able to adapt the aerodynamics of the bank to the different flow rates that pass through the turbojet engine under test. Advantageously, the cylindrical portion is a circular cylindrical portion, the outlet nozzle forming a truncated cone flaring inwardly from said cylindrical portion.

More advantageously, the outlet section of said truncated cone varies between the section of said cylindrical portion and a smaller section. In a preferred embodiment, the outlet nozzle is formed by a circumferential succession of movable flaps, said flaps being articulated about an axis tangent to said cylindrical portion.

Preferably said flaps have a trapezoidal shape and are contiguous in the fully closed position of the outlet nozzle. More preferably the exit cone comprises two sets of movable flaps, each articulated about an axis tangent to said cylindrical portion, the flaps of a second series being superimposed on the flaps of the first series and angularly offset relative thereto.

This configuration eliminates inter-flap leakage when the outlet section is larger than the closed full section. Preferably the flaps of the two series have a trapezoidal shape, the flaps of each of the series being contiguous in the closed full position of the outlet nozzle. More preferably the flaps of the two series have the same trapezoidal shape.

In a particular embodiment the movement of the flaps of the second series, respectively of the first series, is generated by the movement of the flaps of the first series, respectively of the second series. The invention also relates to a test bench comprising a test room adapted to receive a turbojet and an exhaust room separated from the test room by a partition, the gas manifold passing through said partition and being adapted to be moved through the partition to be fixed in one of several predetermined positions while maintaining a relative tightness between the test room and the exhaust room, the test bench comprising a gas collector as described above above. Presentation of the Figures The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent in the following detailed explanatory description of an embodiment of the given invention. by way of purely illustrative and non-limiting example, with reference to the accompanying schematic drawings.

In these drawings: FIG. 1 is a general view, from the front, of a closed turbojet engine test bench; - Figure 2 is a detail view, in section, of Figure 1, showing the test room and the gas manifold; FIG. 3 is a front view of a gas collector according to one embodiment of the invention; FIG. 4 is a perspective view of the gas manifold of FIG. 3, in the configuration for a small turbojet engine; FIG. 5 is a perspective view of the gas manifold of FIG. 3, in the configuration for a large turbojet engine; FIG. 6 is a front view, respectively, of a controlled flap and a follower flap for the production of the gas collector of FIG. 3, and FIG. 7 is a front view of an assembly of FIG. controlled shutters and follower flaps, for producing the gas manifold of FIG. 3. DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION Referring to FIG. 1, a closed bench is shown for carrying out ground tests. on a turbojet engine 1. This bench comprises, firstly, upstream (the upstream and downstream terms referring in the following description to the direction of flow of air in the turbojet engine), an intake chamber of Air 100. This comprises a vertical air intake chimney 101 and an upstream room 102 for supplying the test room 200 where the turbojet engine under test is located. Between the inlet duct 101 and the upstream room 102 are typically positioned airflow rectifying devices 103 which provide a deflection of this air, from its vertical direction to a horizontal direction, to reduce the aerodynamic losses associated with this. change of direction.

Exiting the admission room 100, the air enters the test room 200 itself, in which is positioned the turbojet engine 1 to be evaluated and which will be described in more detail with reference to FIG. this turbojet engine 1 is arranged a gas manifold 2 which is intended to channel the gases from the turbojet engine and the flux induced by these gases. A partition 201 separates the test room 200 from the exhaust room 300 which follows it. This partition is traversed by the gas manifold 2 which can be moved longitudinally through it to be fixed in one of several predetermined positions, while maintaining a relative tightness between the test room and the exhaust room. In other words, the gas manifold 2 is almost the only passage for gas passing from the test room to the exhaust room. In addition to its sealing function, the partition 201 may be provided to provide a structural support function of the gas manifold 2.

At the exit of the test room 200, the gases coming from the turbojet and the induced flow pass into the exhaust chamber 300 which has a substantially mirror shape of the admission room 100, that is to say that it comprises a first room, horizontal, exhaust 301 which opens into a vertical chimney 302 gas ejection outwardly.

Referring now to Figure 2, we see the turbojet test 1 which is positioned on a base 3; this base generally comprises a device for measuring the thrust exerted by the turbojet, known as the thrust scale. In the version shown, the turbojet engine is placed on a base; in alternative embodiments of a test bench, it can be suspended from a gantry which is fixed to the ceiling of the test room, as shown in Figure 1. Downstream of the turbojet engine is placed the collector gas 2, which consists of a frustoconical body, forming inlet flag 4, continuing downstream by a cylindrical body 5 and ending in an outlet nozzle 6 in the form of frustoconical nozzle. As indicated above, this gas collector is displaceable in translation along the axis of the turbojet, in order to optimize the flow of gases from the nozzle of the turbojet engine and the air induced by this gas flow.

On the aerodynamic level, the air circulating in the test room is divided mainly into two streams: on the one hand, a primary flow 10 which is sucked by the turbojet engine and which leaves through the nozzle in the form of a jet 11 of hot gas, and, secondly, an induced flux 12 which is sucked into the room 1 by the drive of the primary flow. This induced flow circulates around the turbojet and enters the gas manifold 2 surrounding the jet 11; it then mixes with the primary flow at the outlet of the gas manifold and especially in the mixing tube. Finally a parasitic circulation, called recirculation flow 13, makes up a portion of the air exiting through the turbojet nozzle upstream, where it can be caught by the air inlet and reinjected into the vein of the turbojet engine. . Various techniques known to those skilled in the art are implemented to minimize or cancel this recirculation flow. While the primary flow 10 fits diametrically at the inlet of the turbojet engine on the corolla of the air intake bell, the induced flow 12 fits on the roof 4 of the gas manifold 2. FIG. , in front view, a gas manifold 2 according to the invention. It comprises a corolla-shaped air inlet 4 which flares upstream in order to capture the jet 11 and a maximum of flux induced 12 to avoid recirculation 13. This corolla 4 is illustrated on FIG. Figure 3, without this configuration is imperative, by the juxtaposition of two cone frustums of different openings, which extend being adjacent. Downstream, this corolla 4 is extended by a circular cylinder 5, of constant section, the length of which is adapted to improve the homogeneity of the mixture of jet flows 11 and induces 12. The gas manifold 2 has an axis central symmetry which coincides with the axis of the circular cylinder 5, and which extends substantially horizontally in the configuration shown. Finally, downstream of this cylindrical portion 5, the gas manifold 2 comprises a frustoconical nozzle 6 which reduces the passage section of the gas mixture. This section is larger or smaller depending on the flow of air flowing in the turbojet engine under test; the value of this section allows an optimization of the flow in the test bench because of the aerodynamic adaptation that it produces between the flow which is derived from the turbojet engine and that which passes through the gas manifold. According to the invention, the angle formed by the frustoconical nozzle 6 with the central axis of the gas collector, that is to say half of the angle at the apex of the virtual cone formed by the frustoconical nozzle, is variable to allow, with the same collector, to test turbojets of different sizes. A modification of this angle, by more or less turning flaps, changes the aerodynamic characteristics of the bench and makes it compatible with a new turbojet under test. In what follows, the outlet cone is called the frustoconical nozzle 6, without the frustoconical shape being imperative. FIGS. 4 and 5 show the exit cone 6 of the collector 2 according to the invention, in the cases, respectively, of a use for a small turbojet engine (and therefore of a small throughput) and for a large turbojet engine. (with high throughput). The exit cone 6 is made in the form of an annular double row of flaps, controlled flaps 7 and follower flaps 8, which are superposed and staggered in a staggered manner. The flaps of the same row are attached by one of their end to the downstream end of the cylindrical body 5 and are rotatable about an axis tangential to the circle formed by said downstream end of the body 5. They can thus be oriented more or less to the central axis of the gas manifold and close more or less the outlet section of this manifold. By tangential axis is meant not only an axis tangent to the purely geometric sense, that is to say a straight line having a point of contact with the outer surface of the cylindrical body 5, but also an axis parallel to said straight line and somewhat offset radially outwardly or inwardly of the body 5.

The controlled flaps 7 may be actuated mechanically by a system of links, or cams, by a system of pneumatic or electric actuators, or by any other control system. As for the follower flaps 8, they are mechanically connected to the shutters 7 controlled by a connecting device whose design can be in itself similar to that of known connection devices in variable section nozzles, such as turbojets jet nozzles. military aircraft. A flap control and link system for example such as that described in FR2877052B1 is appropriate.

In Figure 4 the cone 6 is shown in its minimum section position; this is adapted to the flow passing through a small turbojet engine, whereas in FIG. 5, the cone is shown in its fully open position and its section is then adapted to a large turbojet engine. In the position of FIG. 4, the flaps of the same row, both the controlled flaps 7 and the follower flaps 8, are joined, their trapezoidal shape being defined for this purpose. This gives the minimum output section that can be given to the gas manifold. In contrast, in the position of FIG. 5, the flaps of the same row, both the controlled flaps 7 and the follower flaps 8, are parallel to the axis of the cylindrical body 5 and the output section obtained is maximum because it equals or almost equal to that of this cylindrical body. The flaps are then not joined but the continuity of the vein is ensured by the offset of the follower flaps 8 relative to the controlled flaps 7. Advantageously, the median axis of a follower flap 8 coincides approximately with the median axis of a triangle formed by an oblique side of a controlled flap 7 and the adjacent oblique side on an adjacent controlled flap. As represented the follower flaps are positioned inside the controlled shutters. Advantageously, the controlled shutter control system is installed outside the cylindrical body 5 and at the downstream end of the body, so as to operate the shutters controlled while limiting the size of the system. The follower flaps could equally well be positioned outside the controlled flaps, provided to provide a control system whose actuators, including for example rods articulated on the controlled flaps, are not hindered by the flaps followers to operate the shutters ordered. FIG. 6 shows the shape chosen for both controlled flaps 7 and 8 followers. The same shape is chosen, preferably for the two series corresponding to the two rows of flaps. As indicated above, this shape is, in plan, substantially that of an isosceles trapezoid whose shape depends on the number of controlled flaps (or followers) as well as upstream and ejection sections desired. The length of the flaps depends on the contraction ratio between the upstream section, which substantially corresponds to the section of the cylindrical body 5, and the minimum downstream section with the flaps contiguous, as well as the steering angle retained for the flaps. The long side 7a or 8a is dimensioned so that the length of a series of flaps is substantially equal to the circumference of the cylindrical body 5; as for the small side 7b or 8b, it is dimensioned so that the length of this series is substantially equal to the circumference of the smallest output section envisaged. The oblique sides 7c and 8c of the trapezium are dimensioned so as to ensure a smooth aerodynamic transition for the passage of gases between the cylindrical body 5 and the exit cone 6.

Finally, Figure 7 shows a set of controlled flaps 7 and follower flaps 8 assembled at the downstream end of the cylindrical body 5, in the position where the output section obtained is maximum and therefore adapted to a high power turbojet. The controlled flaps 7, which appear in the chosen configuration, outside the follower flaps 8, are contiguous only at their long sides 7a while their small sides 7b are disjoint and let appear between them the small side 8b flaps 8. The lateral extension of the controlled flaps 7 and followers 8 is such that they provide a covering over their entire length and form a continuous wall for the gas at the outlet cone 6. The principle of the invention thus consists of to provide a gas manifold whose diameter of the cylindrical body 5 is adapted to the air flow of a large turbojet engine and to add a frustoconical portion downstream 6 adjustable section. The adaptability of the ejection section is obtained by means of a set of controlled flaps 7 and a set of follower flaps 8, preferably of the same number, which more or less obstruct the exit section and thus reduce the Aerodynamically effective section of the collector. The value of the two sections, full open or full closed, is chosen to correspond to the two extreme versions of size of turbojet that one is likely to want to implement on this test bench. When the output section is set to the maximum of its closure, the controlled flaps 7 are perfectly contiguous, ensuring perfect circularity in the ejection plane. When the outlet section is open at its maximum, and equal to that of the cylinder 5, the controlled flaps 7 are no longer contiguous and have a non-negligible cross-flap leakage section. This problem is solved in the invention by the addition of follower flaps, which are located on or under the controlled flaps, and which are arranged staggered with respect thereto. They thus make it possible to eliminate the leaks and to ensure again the circularity of the ejection section.

The invention thus makes it possible to define a single gas manifold for the test bench, which is sufficiently open to be able to test large turbojet engines and not be limited in flow, and which is adjustable so that it can be used with additional turbojet engines. small size. The gas manifold according to the invention can then be clamped for certain uses, while maintaining maximum efficiency, and it allows to return in a very fast time in a configuration adapted to another turbojet, without any material degradation and without that there is a need for specific tools. No additional bench adaptation part is indeed to be made between the cycles of two different turbojet engines, which induces a significant time saving for the user. In addition, the gas manifold makes it possible to optimize the adaptation of the test bench to the turbojet, by adding a degree of freedom at the time of the tests carried out on a new type of turbojet engine. This optimal adaptation can be obtained in situ, by successive adjustments of the outlet section of the gas collector, whereas previously this section was obtained on the basis of partial simulations and was then frozen before the introduction of the turbojet engine in the bank. 'essais.20

Claims (10)

REVENDICATIONS1. A gas manifold for a turbojet engine test bench comprising an inlet bell (4) and a cylindrical part (5) contiguous downstream of said bell, characterized in that it further comprises, downstream of the cylindrical part, a outlet nozzle (6) with variable section. The gas manifold of claim 1 wherein the cylindrical portion (5) is a circular cylindrical portion, the outlet nozzle forming a frustum (6) flaring inwardly from said cylindrical portion (5). ). 3. A gas manifold according to claim 2 wherein the outlet section of said truncated cone (6) varies between the section of said cylindrical portion (5) and a smaller section. 4. A gas manifold according to claim 3 wherein the outlet nozzle (6) is formed by a circumferential succession of movable flaps (7), said flaps being articulated each about an axis tangential to said cylindrical portion (5). The gas manifold of claim 4 wherein said flaps are trapezoidal in shape and contiguous in the fully closed position of the outlet nozzle (6). 6. Gas manifold according to one of claims 4 or 5 wherein the outlet nozzle (6) comprises two sets of movable flaps, the flaps of a first series (7) being superimposed on the flaps of the second series (8). ) and angularly offset from them. 7. A gas manifold according to claim 6 wherein the flaps of the two series are trapezoidal, the flaps of each series being joined in the fully closed position of the outlet nozzle (6). 8. Gas collector according to claim 7 wherein the flaps of the two series have the same trapezoidal shape. 9. Gas manifold according to one of claims 6 to 8 wherein the movement of the flaps of the second series (8), respectively of the first series, is generated by the movement of the flaps of the first series (7), respectively of the second series. 10. Turbofan test bench comprising a test room (200) adapted to receive a turbojet (1) and an exhaust room (300) separated from the test room (200) by a partition (201) , the gas manifold (2) passing through said partition and being adapted to be moved through the partition to be fixed in one of several predetermined positions while maintaining a relative tightness between the test room and the exhaust room, said test bench comprising a gas manifold (2) according to one of claims 1 to 9.