ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE, IN PARTICULAR FOR A TEST BENCH, COMPRISING A ROTATING PART ON WHICH IS MOUNTED A FLOATING PART EQUIPPED WITH A MEASURING HEAD

Abstract

The invention relates to an assembly (100) for an aircraft turbomachine, in particular for a test bench, comprising a rotating part (20) comprising: - a drive shaft (8); - a plurality of rotating blades (14); - a rotating aerodynamic fairing (12), the assembly further comprising a floating part (120) rotatably mounted relative to the rotating part (20), the floating part (120) comprising a floating support (36) and a floating measuring head (34) of a device (34a) for measuring at least one characteristic of the gas flow (10a), the floating part (120) being configured so as to have an eccentric center of gravity, so as to return the floating measuring head (34) to a reference angular position. Figure for the abstract: Fig. 2

Description

Title of the invention: ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE, IN PARTICULAR FOR A TEST BENCH, COMPRISING A ROTATING PART ON WHICH IS MOUNTED A FLOATING PART EQUIPPED WITH A MEASURING HEAD Technical field

[0001] The invention relates to the field of aircraft turbomachines, and more precisely to the field of test benches and the measurement of at least one characteristic of a gas flow following a fairing of the turbomachine.

[0002] The invention finds applications in any type of aircraft turbomachine, such as turbojets or turboprops, and in particular turbomachines comprising a rotating aerodynamic fairing, defining an external surface intended to be matched by the gas flow to be characterized. State of the prior art

[0003] In flight or during the test phase, it proves useful to measure certain characteristics of one or more gas flows of an aircraft turbomachine, such as the pressure and / or the speed and / or the temperature of an air flow following an aerodynamic fairing of the turbomachine.

[0004] For example, measurements may be useful for characterizing the boundary layer of an air flow following an aerodynamic fairing of the turbomachine. To perform these dynamic measurements, a measuring head is generally carried by a stator part of the turbomachine, such as a casing. The measuring head represents a part commonly having the shape of a bar, equipped with several sensors for measuring parameters such as total pressure and temperature. Keeping the head static guarantees the reliability of the measurements performed. Otherwise, the speed of the measuring head would modify, for example, the pressure measurements.

[0005] A difficulty arises when the turbomachine does not offer a stator part in the environment close to the flow to be characterized. For example, in the case of a turbomachine receiver with unshrouded rotating blades, the absence of a casing around the blades prevents the installation of the measuring head. These blades generally project radially from a rotating aerodynamic fairing. The latter could then carry the measuring head, but the reliability of the measurements made would remain too low, due to the rotating, therefore non-static, nature of the measuring head. Statement of the invention

[0006] To address at least partially the drawbacks mentioned above, relating to the embodiments of the prior art, the invention firstly relates to an assembly for an aircraft turbomachine, in particular for a test bench, the assembly being centered on a longitudinal central axis of this assembly, and comprising a rotating part around this longitudinal central axis, the rotating part comprising:

[0007] - a drive shaft;

[0008] - a plurality of rotating blades;

[0009] - a rotating aerodynamic fairing, from which the rotating blades protrude radially outward, the fairing defining an outer surface intended to be matched by a gas flow.

[0010] According to the invention, the assembly further comprises a floating part mounted to rotate relative to the rotating part, along the longitudinal central axis, the floating part comprising:

[0011] - a floating support comprising a circumferential surface intended to be matched by said gas flow;

[0012] - a floating measuring head of a device for measuring at least one characteristic of said gas flow, the measuring head being carried by the floating support,

[0013] the floating part being configured so as to have a center of gravity eccentric with respect to the longitudinal central axis, so as to recall the floating measuring head towards a reference angular position around the longitudinal central axis, during the rotation of the rotating part of the assembly.

[0014] The invention advantageously provides a floating part, also called non-rotating, carrying the measuring head which can thus remain static, or substantially static, while the rotating part of the assembly exerts its rotational movement. The measurements carried out with the head, remaining static, thus prove to be perfectly reliable.

[0015] The principle implemented in the invention, comparable to that of a non-rotating or floating hubcap in the radically different field of motor vehicle wheels, offers a wide choice for the reference angular position of the measuring head.

[0016] The invention preferably provides at least any one of the following optional technical features, implemented in isolation or in combination.

[0017] Preferably, the assembly comprises a rolling bearing interposed between the drive shaft and the floating support.

[0018] Preferably, the rotating aerodynamic fairing has two sections spaced axially from each other, the floating part being arranged axially between the two sections of the rotating aerodynamic fairing.

[0019] Preferably, the measuring head is located upstream of the rotating blades.

[0020] Preferably, the rotating blades are variable pitch.

[0021] Preferably, the rotating blades are unshrouded.

[0022] Preferably, the assembly further comprises a balance wheel rotatably mounted on the floating support, so as to further limit the oscillatory movement of the floating part with an eccentric center of gravity.

[0023] Preferably, the measurements carried out by the measuring head will be transmitted wirelessly to the acquisition device located on the ground, for example by radio transmission.

[0024] The invention also relates to an aircraft turbomachine comprising at least one assembly as described above.

[0025] Preferably, the aircraft turbomachine is a test bench turbomachine, but it could alternatively be a turbomachine intended to be installed on the aircraft, in order to provide its propulsion.

[0026] Finally, the invention also relates to a test installation, comprising such an aircraft turbomachine, as well as a test bench, and an apparatus making it possible to generate the gas flow so that it matches the outer surface of the rotating aerodynamic fairing.

[0027] Other advantages and characteristics of the invention will appear in the detailed non-limiting description below. Brief description of the drawings

[0028] The following detailed description refers to the accompanying drawings in which:

[0029] [Fig.l] is a perspective view of an aircraft turbomachine;

[0030] [Fig.2] is a schematic view in longitudinal section of a part of the turbomachine shown in the preceding figure, in the form of a preferred embodiment of the invention;

[0031] [Fig.3] is a sectional view taken along line 111-111 of [Fig.2]; and

[0032] [Fig.4] is a schematic side view of a turbomachine test installation represented in the previous figures; Detailed description of embodiments

[0033] Referring firstly to [Fig. 1], an aircraft turbomachine 1 is shown. This is a turbojet engine whose receiver 3 comprises an unducted fan 4, preferably located upstream of the turbomachine. Subsequently, the terms “upstream” and “downstream” are given with respect to a main direction 5 of gas flow through this turbomachine, these terms being able to be respectively replaced by the terms “front” and “rear”, with the same meaning.

[0034] With reference to figures 1 and 2, the turbomachine 1 comprises, from upstream to downstream, the unducted fan 4, and a gas generator 6. The latter is conventionally produced using one or more compressors, a combustion chamber, and one or more turbines.

[0035] This gas generator 6 is configured so as to deliver mechanical power to the receiver 3, via a drive shaft 8 centered on the longitudinal central axis X of the turbomachine. In a direct coupling configuration, this shaft 8 may be a shaft of the gas generator 6, or in an indirect coupling configuration, it may be an output shaft of a reducer (not shown), driven by the gas generator 6.

[0036] In operation, a total air flow 10a follows the front part of a rotating aerodynamic fairing 12 of the receiver 3, before passing through rotating blades 14 forming the fan 4. This is an annular row of rotating fan blades 14, each projecting radially outward from an outer surface 13 of the rotating fairing 12, this surface 13 being intended to be followed by the total air flow 10a. In the preferred embodiment which is described, the blades 14 are variable-pitch, that is to say that a rotating part 20 of the turbomachine includes not only the drive shaft 8, the rotating fairing 12, and the fan blades 14, but also devices 22 for controlling the pitch of the blades 14 in incidence.Furthermore, the rotating part 20 comprises arms 24 or other mechanical connecting elements, making it possible to couple in rotation the shaft 8 with the other elements of the rotating part, in particular the fan blades 14 and the fairing 12.

[0037] After passing through the unducted vanes 14, the total flow 10a continues to propagate downstream, before encountering a flow separation nozzle 26. The total flow then divides into a primary air flow 10b entering a primary vein 28b, and into a secondary air flow 10c entering a secondary vein 28c. The latter is not ducted radially outwards, but delimited fictitiously by the ends of unducted outlet guide vanes 30, also called OGV (from the English “Outlet Guide Varies”).

[0038] It is noted that the rotating fairing 12 extends downstream, beyond the fan blades 14, to near the inlet of the primary stream 28b. Consequently, the space available at the stator portion 32 of the turbomachine, upstream of the primary stream 28b, may prove to be non-existent or too narrow to allow the installation of a measuring head intended to characterize the total air flow. In addition, usually, the entire front portion of the receiver upstream of the blades 14, formed by the fairing 12, is also rotating, so that such an installation is not recommended for a measuring head intended to remain static.

[0039] The invention provides a solution allowing the installation of a floating measuring head 34, capable of measuring characteristics of the total air flow 10a, upstream of the non-ducted fan blades 14. More precisely, the measuring head 34 makes it possible to measure the pressure and the temperature of the total air flow 10a, in particular in the boundary layer.

[0040] To do this, the invention relates to an assembly 100 centered on the X axis, comprising the rotating part 20, as well as a floating part 120 specific to the present invention, and integrating the measuring head 34.

[0041] The floating part 120, also called the non-rotating part, functions as a non-rotating hubcap for a motor vehicle wheel, this type of hubcap also being called floating.

[0042] Indeed, the floating part 120 comprises a floating support 36, of generally annular shape centered on the axis X. The internal periphery of this support 36 is carried by a rolling bearing 38, interposed between this support 36 and an upstream end 8a of the shaft 8, which can be produced by several shaft sections, mounted on top of each other.

[0043] Thanks to this rolling bearing 38, the floating part 120 is rotatably mounted relative to the rotating part 20, along the X axis. This in fact allows a relative rotational movement to be obtained between the two parts 20, 120, used so that the floating part 120 remains static or substantially static, while the part 20 rotates around the X axis during operation of the turbomachine. This is the reason why the floating part 120 is also called the non-rotating part. It comprises, at its external periphery, a circumferential surface 40 intended to be matched by the total air flow 10a, and is in the aerodynamic continuity of the external surface 13 of the rotating fairing. The measuring head 34 is carried by the floating support 36, projecting radially outwards from the circumferential surface 40.This head 34 is an integral part of a measuring device 34a, other elements of which may be integrated into the support 36, but preferably arranged more towards the inside so as not to protrude into the flow 10a. In this regard, it is noted that the measuring device 34a may communicate the data measured by the head 34 to a rotating telemetry system 42, for example integrated on or near the arms 24.

[0044] In the preferred embodiment described, the rotating aerodynamic fairing 12 has two sections 12a, 12b axially spaced from each other. The section 12a is located furthest upstream, incorporating the nose of the rotating part 20, while the downstream section 12b is the one from which the fan blades 14 project. Other radial arms 124 can connect the shaft 8 to the upstream section 12a, these arms 124 being arranged upstream of the bearing 38, while the arms 24 are arranged downstream of this same bearing, in order to carry the downstream section 12b as well as the timing control devices 22.

[0045] Between them, the two sections 12a, 12b define a free axial space, in which the floating part 120 is arranged, as is best seen in [Fig. 2]. On either side of this floating part 120, the junctions are preferably flush between the circumferential surface 40 of the floating support 36, and the outer surface 13 of the two sections 12a, 12b.

[0046] The floating part 120 is configured so as to have a center of gravity eccentric with respect to the X axis, for example by having a mass heterogeneity in the circumferential direction. This heterogeneity can for example be obtained by locally varying the thickness of the support, in the radial and / or axial directions. The center of gravity of the floating part 120 is determined so that when the turbomachine stops, by gravity, the support 36 causes the measuring head 34 to occupy a reference angular position around the X axis. Indeed, when stopped, the floating part 120 automatically places itself by gravity in a so-called vertical position, in which the center of gravity is aligned vertically with the X axis, in the radial direction.Furthermore, as will be described below, this eccentricity of the center of gravity makes it possible to obtain the floating hubcap effect during operation of the turbomachine, so that the measuring head 34 is permanently recalled towards its reference angular position, despite the rotation of the rotating part 20.

[0047] In [Fig. 3], it has been shown that the reference angular position of the head 34 does not necessarily correspond to a 12 o'clock position. This position can be varied, and adopted according to the needs and constraints encountered, for example by seeking to reduce the wind resistance of the head 34. In the example of this [Fig. 3], the reference angular position corresponds to a 10 o'clock position, but it could of course be different, such as at 3 o'clock, 6 o'clock, etc. In this regard, it is noted that these clockwise positions are given by considering the turbomachine with a normal orientation, that is to say its orientation as observed when it is assembled on the aircraft placed on the ground.

[0048] To reinforce the non-rotating aspect of the floating part 120 in operation, the assembly 100 further comprises a balance 44, or pendulum. It is rotatably mounted on the floating support 36. More precisely, the balance 44 comprises a ring 46 mounted with a small radial clearance 48 around a ring 50 of the floating support 36, this ring 50 preferably being that carried internally by the rolling bearing 38.

[0049] The ring 46 of the balance 44 carries an eccentric mass 52, which also conditions, due to gravity, a vertical rest position of this balance, shown in [Fig.3].

[0050] At rest, due to the small mounting clearance between the two rings 46, 50, the upper part of the ring 46 rests on the upper part of the ring 50. The axis X' of the ring 46 is thus very slightly offset downwards from the axis X of the ring 50, hence the presence of the small radial clearance 48 in the lower part of the two rings 46, 50. This clearance 48 nevertheless remains sufficient to allow relative rotation between the two rings 46, 50, guaranteeing the principle of movement compensation described below.

[0051] Also, when the rotating part 20 is not rotating, namely when the turbomachine is stopped, the floating part 120 adopts its reference angular position, dictated by the position of its center of gravity.

[0052] During operation of the turbomachine, causing the rotating part 20 to rotate around the axis X, the floating part 120 may have a tendency to undergo an oscillating movement around the reference angular position of the measuring head 34. It is the eccentricity of its center of gravity which permanently returns the head 34 towards this reference angular position, allowing this head to maintain a substantially constant angular position, for efficient and reliable measurement on the air flow 10a, upstream of the fan blades 14.

[0053] The presence of the balance 44, rotatably mounted on the floating support 36, makes it possible to further reduce the parasitic movement of the measuring head 34, according to a known principle described in document WO 2000 020231 AL

[0054] Indeed, it is first of all indicated that due to the different eccentricity distances for the center of gravity C1 of the floating part 120, and the center of gravity C2 of the balance 44 less distant from the axis X, these two elements have a tendency to want to oscillate according to distinct oscillation periods, always around their reference angular positions shown in [Fig. 3]. Initially, due to the friction force exerted between these two elements at the level of their respective rings 46, 50 in contact, no relative movement is observed between them, and the measuring head 34 is advantageously stabilized in or close to its reference angular position.

[0055] Furthermore, when the friction force is no longer sufficient and the two elements 120, 44 oscillate, they may then be caused to exhibit opposite directions of rotation during these oscillation movements. When this occurs, the friction force between the two elements 120, 44 causes each of them to oppose the movement of the other. The oscillation amplitudes are then advantageously reduced. By thus reducing the unwanted movements of the measuring head 34, the latter remains non-rotating despite the high-speed rotation of the rotating part 20 of the turbomachine. The dynamic measurements carried out in this way on the flow 10a, with the head 34 static or substantially static, are even more reliable and more efficient.

[0056] Finally, it is observed that if the principle of the invention can be implemented on a turbomachine intended to be installed on an aircraft, in order to ensure its propulsion, the preferred application of the invention nevertheless lies in a turbomachine for a test bench. In this regard, [Fig. 4] schematically represents a test installation 200, for example intended for testing and / or certification of the turbomachine.

[0057] The installation then comprises the turbomachine 1, as well as a test bench 150, and an apparatus 152 making it possible to generate the total air flow 10a, so that it matches the external surface 13 of the rotating aerodynamic fairing 12. The apparatus 12 can be a conventional wind tunnel.

[0058] Various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples, and the scope of which is defined by the appended claims. In particular, other types of turbomachines may be envisaged, preferably with an unducted receiver, driven directly or indirectly by the gas generator, for example of a double-body and / or double-flow design. Furthermore, other solutions than that of the balance 44 may be implemented to contribute to the stabilization of the floating part 120, such as magnetic solutions, or other solutions known in the field of floating hubcaps for motor vehicle wheels.

Claims

Claims

1. Assembly (100) for an aircraft turbomachine, in particular for a test bench, the assembly being centered on a longitudinal central axis (X) of this assembly, and comprising a rotating part (20) around this longitudinal central axis (X), the rotating part comprising: - a drive shaft (8); - a plurality of rotating blades (14); - a rotating aerodynamic fairing (12), from which the rotating blades (14) project radially outwards, the fairing defining an outer surface (13) intended to be matched by a gas flow (10a), characterized in that the assembly further comprises a floating part (120) rotatably mounted relative to the rotating part (20), along the longitudinal central axis (X), the floating part (120) comprising: - a floating support (36) comprising a circumferential surface (40) intended to be matched by said gas flow (10a);- a floating measuring head (34) of a device (34a) for measuring at least one characteristic of said gas flow (10a), the measuring head being carried by the floating support (36), the floating part (120) being configured so as to have a center of gravity eccentric with respect to the longitudinal central axis (X), so as to return the floating measuring head (34) to a reference angular position around the longitudinal central axis (X), during the rotation of the rotating part (20) of the assembly.;

2. Assembly according to claim 1, characterized in that it comprises a rolling bearing (38) interposed between the drive shaft (8) and the floating support (36).

3. Assembly according to claim 1 or 2, characterized in that the rotating aerodynamic fairing (12) has two sections (12a, 12b) axially spaced from each other, the floating part (120) being arranged axially between the two sections (12a, 12b) of the rotating aerodynamic fairing.

4. Assembly according to any one of the preceding claims, characterized in that the measuring head (34) is located upstream of the rotating blades (14).

5. Assembly according to any one of the preceding claims, characterized in that the rotating blades (14) are variable-pitch.

6. Assembly according to any one of the preceding claims, characterized in that the rotating blades (14) are non-ducted.

7. Assembly according to any one of the preceding claims, characterized in that it further comprises a balance (44) rotatably mounted on the floating support (36).

8. Aircraft turbomachine (1) comprising at least one assembly (100) according to any one of the preceding claims.

9. 9. Test installation (200), comprising an aircraft turbomachine (1) according to the preceding claim, as well as a test bench (150), and an apparatus (152) making it possible to generate the gas flow (10a) so that it matches the outer surface (13) of the rotating aerodynamic fairing (12).

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