Aircraft propulsion assembly comprising an air flow valve with a variable flow rate

A propulsion assembly having a heat exchanger and a system for supplying cold air including an air inlet in a stream of air, an air duct connecting the air inlet fluidly to the exchanger, and an air flow valve with a variable flow rate inside the duct, the valve including a hub having blades projecting radially from the hub forming a helix, each blade having a root mounted rotatably on the hub, the valve comprising an electric motor to drive the hub by a motor shaft, and structure for varying pitch angle of the blades, the extremity of each blade being flush with a wall of the duct, the valve controllable to a closed configuration where pitch angle of the blades is 0° and the valve prevents passage of air, an open configuration where pitch angle is 90°, and/or a charge configuration where pitch angle is between 0° and 90°.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to French patent application No. 14 53325 filed on Apr. 14, 2014, the entire disclosure of which is incorporated by reference herein.

BACKGROUND

The disclosure herein relates to an aircraft propulsion assembly comprising a turbofan engine having an air flow valve with a variable flow rate intended to supply air to a heat exchanger.

In a manner known per se, an aircraft propulsion assembly comprises a bleed air system in the area of the turbomachine engine in order to provide a supply of air to the systems which use air, for example such as the cabin air exchange and pressure regulation system.

In order to ensure that the temperature of the air at the exit from the bleed air system remains within the acceptable limits for the user systems, the bleed air system comprises a heat exchanger (PCE for precooler:cooler) allowing the hot air that is bled at the engine to be cooled thanks to the cold air that is bled in the secondary stream of air of the turbomachine. The cold air is bled by a system for the supply of cold air comprising an air inlet arranged in the secondary stream of air, a duct connecting the air inlet to the exchanger, and an air flow valve with a variable flow rate of the butterfly type. The butterfly or movable flap is positioned inside the duct and provides the possibility, by its rotation, for adjusting the rate of flow of the system for the supply of air depending on the requirements of the user systems.

It will be appreciated that such a system for the supply of air does not provide the exchanger with a rate of flow of cold air sufficient to enable the latter to cool the air that is bled at the engine in the case of a propulsion assembly having a turbomachine with a high dilution ratio.

A suitable solution for such propulsion assemblies would be to increase the exchange surface of the exchanger and the dimensions of the air inlet and of the duct. This solution is not viable, however, since the space available for the arrangement of elements inside a propulsion assembly is very limited. The need accordingly exists for a system for the supply of cold air that is more efficient while retaining substantially the same dimensions as the current systems.

SUMMARY

One of the objects of the present disclosure is to overcome the above-mentioned disadvantage in full or in part. For this purpose, the disclosure herein relates to a propulsion assembly comprising a turbomachine and a pylon, the turbomachine comprising an engine attached to the pylon, an annular interstream shroud surrounding the engine and an annular nacelle disposed coaxially around and radially towards the exterior in relation to the interstream shroud, in such a way as to delimit together with the latter a stream of air, the turbomachine comprising a heat exchanger and a system for the supply of cold air, the system comprising an air inlet placed in the stream of air, an air duct connecting the air inlet fluidly to the exchanger, and an air flow valve with a variable flow rate placed inside the duct, the valve comprising a hub, on which there are mounted at least three blades projecting radially from the hub in order to form a helix, each blade having a root mounted rotatably on the hub, the valve in addition comprising an electric motor configured to drive the hub by a motor shaft, and structure for varying the pitch angle of the blades, the extremity of each blade being flush with a wall of the duct, the valve being controllable to adopt one of the following configurations:a configuration known as a closed configuration, in which the pitch angle of the blades is 0° and in which the valve prevents the passage of the air through the duct;a configuration known as an open configuration, in which the pitch angle of the blades is 90° and in which the valve completely opens the access to the air duct;a configuration known as a charge configuration, in which the pitch angle of the blades lies in the range between 0° and 90°.

A principal advantage of the disclosure herein in relation to the existing systems for the supply of cold air consists of the air flow valve according to the disclosure herein allowing a charge configuration in addition. This configuration makes it possible to respond to the requirements for cold air of the user systems when the temperatures reached inside the engine are high. The system for the supply of air according to the disclosure herein is thus suitable for an application in turbomachines with a high dilution ratio.

DETAILED DESCRIPTION

With reference toFIG. 1, a propulsion assembly P comprises a turbofan engine1and its system of attachment, or pylon200, to a wing of the aircraft (not depicted here).

The turbomachine comprises an annular nacelle3, centered on a longitudinal axis X, and an engine2surrounded by the nacelle3and secured to the pylon. The engine2is secured to the nacelle3by two diametrically opposed bifurcations16,17which make it possible to ensure the mechanical cohesion of the turbomachine1.

In the direction of flow of an air flow passing through the turbomachine1and indicated by the arrow F inFIG. 1, the engine2comprises, centered on the longitudinal axis X, a fan5, a motor casing6and a nozzle7.

The motor casing6comprises elements permitting the fan5to be caused to rotate when the engine2is set in motion. These elements are, in the direction indicated by the arrow F, a low-pressure compressor9, a high-pressure compressor10, a combustion chamber11, a high-pressure turbine12and a low-pressure turbine13.

The turbomachine1comprises in addition, downstream of the fan5, an annular interstream shroud8that is concentric with the motor casing6and, together with the latter, delimits an annular airflow path, known as the primary flow path20.

The nacelle3constitutes the external envelope of the turbomachine1and surrounds the interstream shroud8, with which it is concentric. The nacelle3thus delimits, together with the interstream shroud8, an annular flow path, known as the secondary flow path30. The flow paths20and30extend as far as a point downstream of the low-pressure turbine13, that is to say in the area of the nozzle7.

With reference toFIGS. 1 and 2, the propulsion assembly P comprises, in a manner known per se, a system100for bleeding air in the area of the engine6of the turbomachine intended for the purpose of supplying air to one or a plurality of systems60which use air.

The system for bleeding air100comprises the following, for example arranged in the thickness of the interstream shroud8:a first air intake101intended to bleed, in the high-pressure compressor, air at intermediate pressure;a second air intake102intended to bleed, in the high-pressure compressor18, air at high pressure;a non-return valve103connected fluidly to the first air inlet, and which prevents the air from traveling towards the first air inlet101;a high-pressure valve104connected fluidly to the second air inlet102and controlled alternately for opening or for closing;a regulating valve105intended to regulate the pressure of the flow of air which passes through it, the outlet from the high-pressure valve and the outlet from the non-return valve being connected fluidly to the same inlet of the regulating valve105;an exchanger107intended to cool the air which passes through it. The outlet from the regulating valve105is connected fluidly to an inlet to the exchanger107and an outlet from the exchanger107is connected fluidly to at least one system60which consumes air;a system for the supply of cold air200intended to supply cold air to the exchanger107, anda controller106depicted inFIG. 2, of the central processing unit type, intended to control the degree of opening of the valves in the system for bleeding and controlling the flow of air supplied by the system for the supply of cold air200.

The system for the supply of cold air200comprises an air inlet201arranged downstream of the fan5in the secondary flow path30, an air duct202connecting the exchanger107to the air inlet201, and a valve203with a variable flow rate arranged in the air duct109.

According to the disclosure herein, and with reference toFIGS. 3 to 8, the valve203with a variable flow rate comprises an electric motor204, a hub205that is caused to rotate by the motor and is equipped with a plurality of blades206projecting radially from the hub in order to form a helix, as well as structure for varying the pitch angle of the blades207. The electric motor204as well as the structure for varying the pitch angle of the blades207are controlled by the controller106. In the example illustrated inFIGS. 3 to 8, the hub205is situated upstream in the direction of flow of a flow of air passing through the valve towards the exchanger and indicated by the arrow T in the figures, while the motor204is situated downstream in the direction T.

The motor204comprises a motor casing204a,a frame204band an essentially cylindrical motor shaft204ccoupled to the hub205. The frame is dimensioned in such a way that the motor shaft204cis situated at the center of a section of the duct202with its longitudinal axis, or the axis of rotation L of the motor shaft, being substantially parallel to the direction of flow of a flow of air passing through the valve towards the exchanger T. The frame204bis formed, for example, by four individually perpendicular arms, each of the arms being secured both to the wall of the duct202and to the motor casing204a.

The hub205is secured to the extremity of the motor shaft204cand comprises at least three blades206extending radially from the external envelope of the hub205. In the example illustrated inFIGS. 4 to 8, the hub205comprises 8 blades.

Each blade206is profiled and has a root206′ secured to the hub205. In addition, the extremity (blade tip)206″ of each blade is flush with the wall of the duct202. According to the disclosure herein, the root206′ of each blade is rotatably mounted on the hub205so that the pitch angle of the blades may be modified by the structure for varying the pitch angle of the blades207. In a manner known per se, the expression pitch angle of a blade is used to denote the angle formed between the reference chord of the profile of a blade and the plane of rotation of the helix, the plane of rotation of the helix being perpendicular to the axis of rotation L of the motor shaft.

It should be noted that the hub205is arranged on motor shaft204cof the motor so that the leading edge of the blades is situated upstream in the direction of flow of the flow of air passing through the duct T.

The structure for varying the pitch angle of the blades207illustrated inFIG. 5comprises a ring208, eight transmission rods209associated with eight levers210, each of which is coupled to a blade206, a servomotor211(not visible inFIG. 5) and an actuating lever212attached to the servomotor211.

The ring208is mounted on the motor shaft204cbetween the motor casing204aand the hub205. The ring208comprises a throat208′ realized on its external diameter and comprises grooves arranged on its internal diameter (not depicted here). These grooves interact with grooves made on the motor shaft204cof the motor204so that the ring208is integral in rotation with the motor shaft204cbut is also capable of displacement in translation on the latter in the axis of rotation L of the motor shaft.

The servomotor211is configured, when it is actuated, in order to cause a substantially cylindrical motor shaft213to rotate. The servomotor211is situated advantageously outside the duct202in order not to disrupt the flow of the fluids at that point.

The actuating lever212is situated in the prolongation of the motor shaft213of the servomotor211and is supported by two support arms214that are spaced apart from one another and are each attached to the motor casing204b.Each support arm214comprises a transcurrent hole, which is aligned with the transcurrent hole of the other support and which has an axis perpendicular to the axis of rotation L of the motor shaft. The actuating lever212is introduced into the hole of each of the supports214and is thus capable of rotation on an axis perpendicular to the axis of rotation L of the motor shaft.

Furthermore, the actuating lever212comprises two actuating arms216that are spaced apart from one another by a distance that is substantially equal to the external diameter of the ring208. Each of the actuating arms216comprises at its free extremity a roller217that is capable of rotation and is inserted into the throat208′ of the ring208, in which it is able to roll.

Each lever210is attached to the root206′ of a blade206. Each transmission rod209is disposed substantially parallel to the axis of rotation L and is attached at a first extremity to a lever210via a pivoting linkage having a pivoting axis perpendicular to the axis of rotation L, and at a second extremity to the ring208via a pivoting linkage likewise having a pivoting axis perpendicular to the axis of rotation L of the motor shaft.

The structure or apparatus for varying the pitch angle of the blades207operates according to the following principle: rotation of the motor shaft213of the servomotor causes rotation of the actuating lever212and thus of the two actuating arms216. The rotation of the actuating arms brings about, via the rollers217inserted into the throat208′, a displacement of the ring208, which is constrained in translation, on the motor shaft204c.The displacement of the ring208causes the displacement of the transmission rods209and thus, by the levers210, causes rotation of the root206′ of the blades about their chord line. According to this principle, the pitch angle of the blades206varies between two extreme angles:an angle of 0°, at which the blades206close the duct202in a practically sealed manner, as depicted inFIG. 6; andan angle of 90°, which corresponds to a feathering of the blades206, as depicted inFIG. 7, completely opening the access to the duct.

Thus, for pitch angles other than 0° and 90°, and for an appropriate direction of rotation of the motor shaft, the rotation of the hub205conveys cold air to the exchanger107.

When the turbomachine1is set in motion, the operation of the system for the supply of cold air200, as described above, is as follows: the air is admitted into the turbomachine1via the fan5. Downstream of the fan5, the flow of air divides into one part which flows in the secondary flow path30and another part which utilizes the primary flow path20. In the secondary flow path30, and as a result of the dynamic pressure of the flows of air, one part of the air enters the system for the supply of cold air200in the area of its air inlet201(arrow E).

Depending on a flow of air required by a user system60, the controller106modifies the speed of rotation of the motor204and/or the pitch angle of the blades206in order to adapt the flow of air provided by the system for the supply of cold air200. The following configurations are possible:the closed configuration, depicted inFIG. 6, in which the pitch angle of the blades206is 0°, and where the motor204has not been set in motion. In this configuration, no fluid is bled through the air inlet201because the valve203then prevents the air from circulating from the air inlet201towards the exchanger107. In this configuration, the drag induced by the system for the supply of cold air is minimal;the open configuration, depicted inFIG. 7, where the blades206are feathered, and where the motor204has not been set in motion. In this configuration, fluid is bled via the air inlet201and is conveyed towards the exchanger107via the duct202. Such a configuration is appropriate for the majority of normal operating modes of the turbomachine1; anda charged configuration, depicted inFIG. 8, where the motor204is set in motion and causes the hub205to rotate, and where the blades206have a pitch angle in the range between 0° and 90°, preferably between 35° and 50°. The speed of rotation of the motor is regulated by the controller116in order that the temperature at the exit from the exchanger107(temperature of the flow of air received by the user systems) is equal to a setpoint temperature. In this configuration, the air flow valve with a variable flow rate203acts as a fan which increases the mass of air bled at the air inlet201in order to convey it to the exchanger107. In this configuration, the flow of air supplied by the valve203is increased or reduced respectively by increasing or reducing the speed of rotation of the motor204. Such a configuration is adopted in order to perform maximum bleeding of cold air in extreme cases where the temperature reached inside the engine is very high. It should be noted that it is in this configuration that the drag induced by the system for the supply of cold air200according to the disclosure herein is at its maximum value.

By way of example, and for systems for the supply of cold air having the same dimensions (air inlet, duct with a diameter of 270 mm), the air flow valve203according to the disclosure herein provides a maximum flow rate of 100 g/s, whereas this flow rate is only 70 g/s for an air flow valve according to the prior art.

An advantage of the disclosure herein in relation to the existing systems for the supply of cold air is that the air flow valve203also permits a charge configuration while retaining dimensions that are substantially identical to the dimensions of the valves of the prior art. This configuration makes it possible to respond to the requirements for cold air of the user systems60when the temperatures reached inside the engine2are high. The system for the supply of cold air200according to the disclosure herein is thus suitable for an application in turbomachines1with a high dilution ratio.

As a variant of the embodiment described above, and in relation toFIG. 9, the hub205is situated downstream in the direction of flow of a flow of air passing through the duct T, while the motor204is situated upstream in the direction T. The hub205is arranged on the motor shaft204cof the motor, so that the leading edge of the blades is situated upstream in the direction of flow of the flow of air passing through the duct T. Thus, for pitch angles other than 0° and 90°, and for an appropriate direction of rotation of the motor shaft, the rotation of the hub205conveys cold air to the exchanger107.

The system for the supply of cold air200may be arranged in a turbomachine assembly P regardless of its architecture.

Thus, in a first architecture illustrated inFIG. 10, the exchanger107is arranged inside the engine pylon200, the air duct202in this case being arranged in part inside the space situated between the nacelle3and the engine pylon200, while the air inlet is situated on the external wall of the secondary flow path30.

In a second architecture illustrated inFIG. 11, the exchanger107is arranged in a bifurcation16, the air duct202in this case being arranged in part inside the thickness of the bifurcation16, while the air inlet is situated on the external wall of the bifurcation16in order to bleed air from the secondary flow path30.

Finally, so as not to slow down the flows of air as they flow inside the duct202, an aerodynamic element300is attached to the element of the air flow valve203that is situated furthest upstream in the direction of flow of a flow of air passing through the duct T. Thus, as illustrated inFIGS. 4 to 8, a cone300is arranged at the extremity of the motor shaft204cof the motor, with its base attached to the hub205, or, as illustrated inFIG. 9, a cone300is arranged on the motor204with its base attached to the casing204aof the motor.