FR3019209A1 - MOVABLE DAWN COMPRISING NOISE REDUCING MEANS - Google Patents

Abstract

The invention proposes a blade (22) movable turbomachine (10) which comprises, in the direction of air flow relative to the blade (22), a leading edge (26) upstream and an edge of downstream leak (28), characterized in that a downstream portion (32) of the vane (22) is formed of a plurality of radially aligned flaps (30), the flaps (30) being hingedly mounted relative to one another. upstream body (34) of the blade (22) about an articulation axis (A) substantially parallel to a main axis of the trailing edge (28), the flaps (30) being movable between an alignment position wherein all the flaps (30) are aligned and at least one offset position in which at least one flap (30) is angularly offset from the alignment position.

Description

TECHNICAL FIELD The invention proposes a turbomachine blade which is shaped to reduce the noise generated by the fan of the turbomachine. The invention also proposes a turbomachine comprising noise reduction means. STATE OF THE PRIOR ART In an aircraft turbomachine, the fan is a part of the turbomachine which is responsible for a large part of the noise produced by the turbomachine. In particular, the noise is produced when the air flow in the wake of the blades of the fan impinges against the vanes fixed by the secondary flow rectifier.

In order to reduce the noise generated, it has been proposed to modify the aerodynamic shape of the blades and / or mobiles. However, a modification of the profile of the blades in order to improve the acoustics of the turbomachine, has an impact on the performance and fuel consumption of the turbomachine.

The invention aims to provide a fan blade that can limit noise, without increasing fuel consumption. PRESENTATION OF THE INVENTION The invention proposes a mobile turbine engine blade which comprises, in the direction of air flow with respect to the blade, an upstream leading edge and a trailing trailing edge, characterized in that a downstream portion of the blade is formed of a plurality of radially aligned flaps, the flaps being mounted articulated relative to an upstream body of the blade around an axis of articulation substantially parallel to a main axis of the edge leakage, the flaps being movable between an alignment position in which all the flaps are aligned and at least one offset position in which at least one flap is offset angularly with respect to the alignment position.

The plurality of flaps at the trailing edge of the blade makes it possible to modify the dimensions of the turbulence in the wake, in order to adjust the noise produced. The fact that the flaps are mobile allows, when the conditions require it, for example during the take-off / landing phases, to limit the noise, and in other operating conditions, for example in high-altitude flight, to favor the performance of the turbomachine. Preferably, the blade comprises drive means flaps moving relative to the upstream body of the blade around said hinge axis. Preferably, each flap is driven by an associated actuator mounted in the body of the blade.

Preferably, the actuator of each flap is an actuator of the piezoelectric type. Preferably, means for electrically connecting the actuators to a source of electricity pass through the body of the blade. Preferably, the number of flaps is between three and ten.

Preferably, the offset angle of a flap relative to its alignment position is in the range [-15 °; 15 °]. The invention also proposes an aircraft turbomachine comprising a fan composed of a plurality of blades according to the invention and a flow rectifier, characterized in that it comprises noise measuring means which are situated downstream of the engine. flow rectifier and a device for controlling the position of the flaps of each blade according to the noise measured and according to the operating conditions of the turbomachine and / or the aircraft. Preferably, the noise measuring means comprise piezoresistive sensors or microphones.

The invention also proposes a method for controlling the flaps of a blade according to the invention, which is mounted in a turbomachine, characterized in that at least one is displaced with respect to the upstream body of the blade and with respect to the flap adjacent during a take-off and / or landing phase.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended figures among which: FIG. 1 is a diagrammatic representation of a part upstream of a turbofan engine comprising a fan provided with blades according to the invention; - Figure 2 is a schematic perspective view of a fan blade according to the invention. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS FIG. 1 shows an aircraft turbomachine 10 which here consists of a double-flow reactor which takes a stream of air which is compressed and is divided into a primary air flow 12 which is intended to circulate in the combustion chamber and a peripheral secondary air flow 14 relative to the primary flow. It will be understood that the invention is not limited to a turbomachine 10 of the double flow type and that it can also be applied to a single-flow turbomachine. The turbomachine 10 comprises a low-pressure compressor 16, commonly known as a "fan", which takes the air flow and gives it an acceleration, and a high-pressure compressor (not shown) located downstream of the low-pressure compressor 16 which allows to increase the pressure of the air flow.

Each high pressure or low pressure compressor 16 comprises a plurality of compression stages, each stage being composed of a plurality of moving blades 22 which are carried by the rotor 24 of the turbomachine 10 and a flow rectifier 18, 20 which redirects the flow of air in the main axis of the turbine engine 10. As can be seen in more detail in FIG. 2, each moving blade 22 has a leading edge 26 which is situated on the upstream side. relative to the direction of flow of the air flow passing through the turbomachine 10 and a trailing edge 28 located on the downstream side with respect to the direction of flow of this air flow. During its rotation around the main axis of the turbomachine, the blade 22 acts on the air flow to give it an acceleration and an inclined orientation relative to the axis of the turbomachine.

Also, the wake of the blade 22 has a particular turbulent structure, which, when it impacts the vanes of the flow rectifier 18, 20, produces a certain noise. When the turbulent structure of the wake of the blade 22 is coherent, that is to say that the air vortices that form from the trailing edge 28 of the blade 22, are large, the noise generated is of high intensity. On the other hand, when the turbulent structure of the wake of the blade 22 is not very coherent, that is to say that the air vortices that form from the trailing edge 28 of the blade 22 are of small dimensions. , the noise generated is of low intensity. In fact, small eddies contain less energy than larger eddies, which results in lower sound pressure. In order for the wake of the blade 22 to be constituted by vortices of smaller dimensions, the downstream portion 32 of the blade 22, whose downstream end edge forms the trailing edge 28, consists of a plurality of flaps 30 which are distributed along the radial main direction of the blade 22. The flaps 30 are mounted articulated relative to an upstream body 34 of the blade 22 located upstream of the downstream portion 32. The flaps 30 thus form a movable assembly of the blade 22 which is articulated with respect to the upstream body 34 about a hinge axis A substantially parallel to a main axis of the trailing edge 28, said hinge axis A being located at the level of the upstream end of the downstream part 32.

The number of flaps 30 is preferably between three and ten. Here, in the embodiment shown in Figure 2, the number of flaps 30 is six. The flaps 30 are movably mounted relative to each other and relative to the upstream body 34 of the blade 22 between an initial alignment position shown in Figure 2, in which all the flaps 30 are aligned with each other , and an active offset position in which at least one flap 30, and preferably several flaps 30 are angularly offset from their alignment position. When the flaps 30 are in the alignment position, their downstream end edges, which form the trailing edge 28 are aligned, so that the trailing edge 28 consists of a single continuous edge. When the flaps 30 are in the offset position, the downstream end edges of the flaps which are angularly offset, are shifted transversely to the initial trailing edge 28, that is to say that these flaps have pivoted around the articulation axis A of a predetermined offset angle. The value of this offset angle is a few degrees, and preferably, it is at most 15 degrees. The pivoting of a flap can be made on either side of the alignment position, the value of the offset angle is therefore in the range [-15 °; 1501.

Beyond this offset angle value, excessive separation of the air flow can occur, which then causes an increase in the noise generated by the turbomachine. When the flaps 30 are in the offset position, the trailing edge resulting from the blade 22 is formed of a plurality of segments offset from one another. The flow of air flowing on both sides of the blade 22, when the flaps 30 are in the offset position, produces a wake very disturbed compared to a wake when the flaps 30 are in their position d 'alignment. The strong disturbances of the wake are characterized by small vortex movements that generate a limited noise when they strike the vanes of the secondary flow rectifier 20, for example. However, these strong disturbances can have an effect limiting the efficiency and the efficiency of the turbomachine 10 under certain operating conditions of the turbomachine. In order to overcome this disadvantage, each blade 22 is advantageously designed such that the position of each flap 30 can be varied between the alignment position and one or more offset positions. The blade 22 comprises for this purpose actuators (not shown) which perform the drive flaps 30 to the required position. Preferably, the blade 22 comprises an actuator associated with each flap 30, which carries out the driving of the associated flap 30, in displacement relative to the upstream body 34 of the blade 22. In order not to have an impact on the flow of the air around the blade 22, the actuators are integrated with the blade 22. Preferably, the actuators are of the piezoelectric type. The blade 22 then comprises power supply means actuators which are mounted through the blade 22, such as for example electrical cables connecting piezoelectric actuators with their energy source and their control means.

The turbomachine 10 also comprises means for controlling the position of the flaps 30 of each vane 22, as a function of the operating conditions of the turbomachine 10. In fact, the reduction of the noise is only necessary for certain operating conditions of the engine. turbomachine 10, such as during takeoff and landing phases of the aircraft, because it is at these times that the noise is the most damaging to the population, while during the high-altitude flight, the noise n is not perceptible to the population. Also, the noise reduction means reduce the efficiency and the efficiency of the turbomachine 10. This is why it is preferable to keep the configuration of the shutters 30 in an offset position only when the noise reduction is required, and to maintain the flaps 30 in the aligned position the rest of the time, that is to say, mainly in flight. The control means of the position of the flaps 30 comprise a computer 38, which is able to determine the operating conditions of the turbomachine, to define whether the noise reduction is required or not, and which is able to define the optimum position of the engines. flaps 30 relative to the upstream body 34 of the blade 22. To determine this optimum position of each flap 30 relative to the body 34 of the blade 22, the computer 38 of the control means preferably integrates a database derived from acoustic tests that have been performed beforehand on different positions and configurations of the flaps 30. A comparison between the target value and the measured value of the noise emitted, as well as a measurement of the operating conditions will allow the computer 38 to define the amplitudes of The pivoting of the flaps 30 may thus vary according to the operating conditions, that is to say that the angles of offset of the flaps 30 may vary. Lets 30, as well as the direction of pivoting can vary from one flap 30 to another, so that two flaps 30 adjacent are angularly offset relative to each other. Also, calculator 38 can determine if one or more flaps 30 should pivot, and which ones. The control means also comprise a sensor 36 for measuring the noise level, or the sound pressure, downstream of the rectifier 18, 20, at the level of which the noise is generated by the airflow downstream of the blades 22, as shown in FIG. 1. The sensor 36 is preferably a piezoresistive microphone or sensor.

Thus, as shown schematically in FIG. 1, after having passed around the blade 22, the airflow produces a turbulent flow (represented by the arrow F1) which comes into contact with the rectifier 18, 20 and produces some noise. This noise is measured by the sensor 36 which then transmits acoustic pressure information to the computer 38 (arrow F2).

The computer 38 then determines what should be the position of each flap 30 relative to the upstream body 34 of the blade 22, and then transmits the pivot controls to the actuating actuators flaps 30 which must pivot (arrow F3). After the flaps 30 are pivoted, a noise having another acoustic pressure is generated, this is again measured by the sensor 36 and, as described above, the sound pressure information is transmitted to the computer 38 so that an adjustment of the positions of the flaps 30 can be carried out if necessary.

Claims (10)

REVENDICATIONS1. Mobile turbine engine blade (22) (10) which comprises, in the direction of air flow with respect to the blade (22), a leading edge (26) upstream and a trailing edge (28) downstream characterized in that a downstream portion (32) of the blade (22) is formed of a plurality of radially aligned flaps (30), the flaps (30) being hingedly mounted relative to an upstream body (34) the blade (22) about an articulation axis (A) substantially parallel to a main axis of the trailing edge (28), the flaps (30) being movable between an alignment position in which all the flaps (30) are aligned and at least one offset position in which at least one flap (30) is angularly offset from the alignment position. 2. blade (22) mobile according to the preceding claim, characterized in that the blade (22) comprises drive means flaps (30) in displacement relative to the upstream body (34) of the blade (22) around said articulation axis (A). 3. blade (22) mobile according to the preceding claim, characterized in that each flap (30) is driven by an associated actuator mounted in the body (34) of the blade (22). 4. Aube (22) mobile according to the preceding claim, characterized in that the actuator of each flap (30) is a piezoelectric type actuator. 5. blade (22) movable according to the preceding claim, characterized in that means for electrically connecting the actuators to a source of electricity through the body (34) of the blade (22). 6. blade (22) movable according to any one of the preceding claims, characterized in that the number of flaps (30) is between three and ten. 7. blade (22) movable according to any one of the preceding claims, characterized in that the offset angle of a flap (30) relative to its alignment position is in the range [-15 ° ; 15 °]. 8. An aircraft turbomachine (10) comprising a compressor (16) composed of a plurality of vanes (22) according to any one of the preceding claims and a flow rectifier (18, 20), characterized in that it further comprises noise measuring means (36) which are situated downstream of the flow rectifier (18, 20) and a device for controlling the position of the flaps (30) of each blade (22) as a function of the noise. measured and according to the operating conditions of the turbomachine (10) and / or the aircraft. 9. Turbine engine (10) according to the preceding claim, characterized in that the noise measuring means (36) comprise piezoresistive sensors or microphones. 10. A method of controlling the flaps (30) of a blade (22) according to any one of claims 1 to 7, which is mounted in a turbomachine (10) according to claim 8 or 9, characterized in that at least a flap (30) is displaced relative to the upstream body (34) of the vane (22) and relative to the flap (30) adjacent during a take-off and / or landing phase.