Rotor assembly suitable for a helicopter and a helicopter equipped with this rotor assembly

Abstract

Rotor assembly (100) for a helicopter comprising a rotating element (110) adapted to rotate about an axis of rotation (150), in which the rotor assembly (100) comprises: - at least one blade (101, 102) fixed to said rotating element (110), the angle of incidence of said at least one blade (101, 102) being adjustable during the rotation of said at least one blade (101, 102) about the axis of rotation (150), - at least one drive arm (103, 104) comprising, on the one hand, a first end connected to the rotating element (110) and an air inlet opening (113, 114) located near said first end, and on the other hand, a second free end and an air outlet opening (123, 124) located near said second free end, said at least one drive arm (103, 104) being adapted to guide an airflow from said air inlet opening (113, 114) to said air outlet opening (123, 124). Figure from the abstract: 3

Description

Title of the invention: Rotor assembly adapted for a helicopter and a helicopter equipped with this rotor assembly. Field of the invention

[0001] The invention relates to a rotor assembly for a helicopter having a rotating element adapted to rotate about an axis of rotation, in which the rotor assembly comprises at least one blade fixed to said rotating element, the angle of incidence of said at least one blade being adjustable during the rotation of said at least one blade about the axis of rotation and at least one drive arm fixed to said rotating element at a first end, said at least one drive arm comprising an air inlet near the connection with the rotating element, and an air outlet near the free end of said at least one drive arm, said at least one drive arm being adapted to conduct an air stream from said air inlet to said air outlet.

[0002] In particular, the invention relates to a rotor assembly forming part of a helicopter propulsion system using hollow bodies, in the form of tubes, for example. In this description, the term "drive arm" is used to refer to these tubes. These drive arms are arranged like the spokes of a wheel on a rotating element adapted to rotate about an axis of rotation.

[0003] The drive arms are equipped, on the one hand, with a pressurized air supply device near the axis of rotation and, on the other hand, with an air outlet near the free end of each drive arm. Thus, pressurized air can be conducted from the air inlet of the drive arms to the air outlet, through the inside of the drive arms. The pressurized air exits the drive arms through the air outlet. Since the air outlet is oriented essentially transversely to the longitudinal direction of the drive arms, the airflow induces a reaction force at the end of the drive arms. This reaction force causes the entire assembly of drive arms and the rotating element to rotate around the axis of rotation.By also connecting the helicopter blades to the rotating element, a rotor assembly is obtained in which the blades rotate thanks to the reaction force exerted by the air when it is expelled at the air outlet of the engine arms. State of the art

[0004] The principle of using pressurized air to rotate the blades of a helicopter is known in the prior art. This principle is thus applied to many helicopters, including the Djinn-type helicopter, in which the pressurized air supply to the injection nozzles, installed at the tips of the rotor, comes from an air intake on the compressor of a turbomachine. The Djinn-type helicopter This system is characterized by its operation on the following principle: the rotor is driven by compressed air ejected from a compressor driven by a gas-generating turbine. This compressed air is injected at the rotor hub and channeled to the blade tips. The absence of reaction at the motor-rotor coupling eliminates the need for a tail rotor. Therefore, all the power produced is used for lift.

[0005] One of the limitations of the Djinn-type helicopter is that its blades perform two different functions. First, the blades are used to generate lift. Second, the blades guide the airflow within them, from an air intake to an air outlet. This means that when manufacturing the blades of a Djinn-type helicopter, a compromise must be found between the shape and material of the blade intended to optimally perform the first function and the shape and material of the blade intended to optimally perform the second function.

[0006] In the prior art, a helicopter as described in patent EP2181036 is also known, in which high-pressure air is used to rotate a rotor assembly, the function relating to the creation of lift and the function relating to the circulation of the airflow being ensured by two different parts of the rotor assembly.

[0007] This patent EP2181036 describes a rotor assembly with at least one blade and at least one drive arm. The blades are used in a conventional manner to generate lift during blade rotation. Independent drive arms are attached at one end to a rotating element of the rotor assembly and are provided with an air inlet for the intake of pressurized air. The drive arms also have an air outlet at their free end. Pressurized air can pass through the inside of the drive arms to the air outlet and be expelled from the drive arms at that point. Due to the reaction force produced on the air outlet, a force is exerted on the drive arms, which generates the rotation of the drive arms and thus, of the entire rotor assembly.

[0008] One of the advantages of the device mentioned in patent EP2181036 is that the shapes and use of materials in the manufacture of the blades and motor arms can be optimized for the specific use of said blades and motor arms.

[0009] Furthermore, the angle of incidence of the blades must always be adjusted during the rotation of the entire rotor, generating a constant variation in the angle of incidence at which the pressurized air is ejected from the blade tip. The drive arm, on the other hand, can be placed in a fixed position on the rotating element. This means that by separating the two functions mentioned on specific blades and drive arms, the air can be directed to the air outlet by drive arms whose angle of incidence is fixed. This This greatly simplifies the construction of the rotor assembly. Furthermore, this structure allows for a constant ejection angle, thus providing improved efficiency.

[0010] During the rotation of a rotor assembly described above according to patent EP2181036 with motor arms, the motor arms rotate around the axis of rotation at the same speed as the blades.

[0011] The present invention aims to exploit this rotation of the motor arms to optimize the operation of the rotor assembly. Summary of the invention

[0012] The invention relates to a rotor assembly for a helicopter comprising a rotating element adapted to rotate about an axis of rotation, in which the rotor assembly comprises:

[0013] - at least one blade fixed to said rotating element, the angle of incidence of said at least a blade being adjustable during the rotation of said at least one blade around the axis of rotation,

[0014] - at least one motor arm comprising, on the one hand, a first connected end to the rotating element and an air inlet opening located near said first end, and on the other hand, a second free end and an air outlet opening located near said second free end, said at least one drive arm being adapted to guide an airflow from said air inlet opening to said air outlet opening, said rotor assembly being characterized in that said at least one drive arm is provided with an ejector, said ejector being positioned circumferentially around the air outlet opening of said at least one drive arm and at a determined distance from the air outlet opening of said at least one drive arm, said ejector comprising an inlet opening and an outlet opening, a primary airflow (Lp) flowing at a primary flow rate (Dp) from the air inlet opening (113,114) towards the air outlet opening of said at least one drive arm and a secondary airflow (Ls) flowing at a secondary flow rate (Ds) from the inlet opening (51) towards the outlet opening through the ejector to form a total airflow (Lt) comprising a total flow rate (Dt) equal to the sum of the primary flow rate (Dp) and the secondary flow rate (Ds). ,

[0015] According to one embodiment of the invention, said at least one motor arm includes a primary channel, for example tubular in shape, to conduct the primary airflow (Lp) from the air inlet opening to the air outlet opening.

[0016] According to one embodiment of the invention, said at least one motor arm comprises a secondary channel and a perforated area to allow the passage of air from the outside of said at least one motor arm to the inside of said secondary channel and said at least one motor arm, the perforated area extending in the longitudinal direction said at least one motor arm.

[0017] According to one embodiment of the invention, the perforated area is provided with one or more perforations.

[0018] According to one embodiment of the invention, the perforations are arranged substantially in a line.

[0019] According to one embodiment of the invention, the perforations are arranged along two or more substantially parallel bands.

[0020] According to one embodiment of the invention, the inner face of the perforated area is connected to the inlet opening of the ejector by said secondary channel.

[0021] According to one embodiment of the invention, said at least one motor arm has a cross-section of substantially aerodynamic shape.

[0022] According to one embodiment of the invention, said at least one motor arm has an aerodynamic profile comprising an intrados and an extrados forming the transverse contour of said at least one motor arm.

[0023] According to a second aspect of the invention, the invention relates to a helicopter equipped with a rotor assembly according to the invention. Brief description of the figures

[0024] The invention, its functionality, its applications and its advantages will be better understood upon reading this description, made with reference to the figures, in which:

[0025] [Fig-1] shows a schematic view of a rotor assembly according to the prior art, comprising two rotors and two drive arms;

[0026] [Fig.2] shows a schematic view of the end of a motor arm with an output air and an ejector placed around the air outlet of the motor arm;

[0027] [Fig.3] shows a schematic view of a rotor assembly with an ejector connected to the inside of a perforated area of ​​the motor arm;

[0028] [Fig.4] shows the exterior of an example embodiment of a motor arm according the invention;

[0029] [Fig.5] shows the cross-section of the drive arm according to [Fig.4], near its free end;

[0030] [Fig. 6] shows a schematic view of the airflow around the motor arm when no air is drawn in through the perforated area;

[0031] [Fig.7] shows a schematic view of the airflow around a motor arm when the air is drawn in through the perforated area. Detailed description

[0032] In this text, the word "helicopter" is used to designate an aeronautical device, or aircraft, which uses a substantially horizontal rotor to generate a Lift. The term helicopter refers to any adapted vehicle that can move freely in the air thanks to the lift created by a rotor.

[0033] In the present text, reference is made to a "drive arm" with an air inlet and an air outlet, the drive arm being adapted to conduct an airflow from the air inlet to the air outlet. It is understood that the term "air" in expressions such as "air inlet," "air outlet," and "airflow" refers to an inlet for a suitable gas, essentially comprising air, which can be conducted from the air inlet to the air outlet under a certain pressure.

[0034] In this text, the term "airflow" refers in particular to the gas flow produced by a gas turbine comprising a compressor, a combustion chamber, and a turbine. The gas flow exiting this gas turbine comprises compressed air and the reaction products of combustion in the combustion chamber.

[0035] Figure 1 schematically represents a rotor assembly 200 according to the prior art, comprising a rotating element 210. A first blade 201 and a second blade 202 are connected to the rotating element 210. The blades 201 and 202 can rotate about their longitudinal axis to change the angle of incidence of the blades 201, 202 during the rotation of the rotating element 210 about the axis of rotation 250. This change in the angle of incidence of the blades is achieved by means of a rotating plate, as is known in the prior art for helicopter blades.

[0036] The rotating element 210 is further provided with a first drive arm 203 and a second drive arm 204. The first drive arm 203 is provided with an air inlet 213 and an air outlet 223. The first drive arm 203 is hollow and adapted to conduct pressurized air from the air inlet 213 to the air outlet 223. The air outlet 223 of the first drive arm 203 is substantially perpendicular to the longitudinal direction of the first drive arm 203. This means that the air flowing from the air outlet 223 of the first drive arm 203 exerts a reaction force on the first drive arm 203, near its end, in a direction perpendicular to the longitudinal direction of the first drive arm 203. Due to this force In reaction, the rotating element 210 rotates in a direction opposite to the direction of the airflow exiting the air outlet 223.This rotation is schematically indicated by arrow 260 on [Fig.l].

[0037] The second drive arm 204 is provided with an air inlet opening 214 and an air outlet opening 224. The second drive arm 204 is hollow and adapted to conduct pressurized air from the air inlet opening 214 to the air outlet opening 224. The air outlet opening 224 of the second drive arm 204 is substantially perpendicular to the longitudinal direction of the second drive arm 204. This means that The air flowing from the air outlet 224 of the second drive arm 204 exerts a reaction force on the second drive arm 204, near its end, in a direction perpendicular to the longitudinal direction of the second drive arm 204. Due to this reaction force, the rotating element rotates in a direction opposite to the direction of the airflow from the air outlet 223. This rotation is schematically indicated in [Fig. 1] by arrow 260.

[0038] As can be seen in [Fig.1], the air outlet 223 of the first motor arm 203 and the air outlet 224 of the second motor arm 204 essentially form an angle of 180° degrees with respect to each other.

[0039] According to the embodiment shown in [Fig. 1], the airflow enabling the rotation of the drive arms 203, 204 is generated by means of a turbojet 300. This turbojet 300 has a rotation axis 301 which is aligned with the rotation axis 250 of the rotating element 210. A connecting element 220, which is substantially Y-shaped, is connected to an outlet opening 310 of the turbojet 300 by means of a swivel joint 320. The central arm of the Y is connected to the outlet opening 310 of the turbojet 300. The upper arms of the Y are connected to the inlet openings 213, 214 of the first and second drive arms 203, 204, respectively.

[0040] Thus, the use of the structure of the rotor assembly 200 described above, and in particular the alignment of the rotation axis 301 of the turbojet 300 with the rotation axis 250 of the rotating element 210, has the consequence that, when the motor arms 203 and 204 and the rotors 201 and 202 are set in rotation, no counter-torque or only a very limited counter-torque is generated in the direction opposite to the direction of rotation of the rotor assembly 200. This means that, in principle, the rotor assembly 200 can be used to create lift for a helicopter without the latter needing to be equipped with a tail rotor to neutralize the aforementioned counter-torque.

[0041] In addition, the construction of the rotor assembly 200 has the advantage of having relatively few moving parts to transmit thrust to the rotating element 210 and consequently to the blades 201 and 202. In other words, the construction of the rotor assembly 200 is simpler than the construction of a traditional helicopter powered by a conventional engine.

[0042] The rotor assembly 200 described above is certainly advantageous due to its simple construction, but nevertheless presents a disadvantage related to the use of the single-flow turbojet engine with significant specific fuel consumption, i.e., fuel consumption relative to the thrust produced. From a commercial standpoint, an aircraft's fuel consumption is of paramount importance because aircraft performance in terms of payload and range is indicated in a catalog intended for users wishing to purchase an aircraft. Thus, the user will prioritize selecting an aircraft with the lowest operating cost. That is to say, an aircraft with the lowest possible fuel consumption. Optimizing an aircraft's fuel consumption is therefore very closely linked to its commercial success.

[0043] The energy lost in the exhaust of a jet engine degrades its propulsive energy. This energy dissipated into the atmosphere is proportional to the airflow rate and also to the square of the exhaust velocity. The aim of the present invention is to minimize this dissipated energy. According to the present invention, a solution is proposed to reduce the energy lost during the ejection of an airflow by the turbojet engine, while maintaining the thrust thus produced. The main objective of this solution is to mix the primary airflow (Dp), exiting the engine arms, with an additional secondary airflow (Ds) at low velocity so that the lost ejection energy is less than the thrust force produced.

[0044] In the present text, reference is made to an "ejector", which is proposed below to improve the performance of an aircraft.

[0045] Figure 2 schematically illustrates the operation of an ejector 5, also called a nozzle 5, at the end of a drive arm 3. The drive arm 3 has an air outlet 23 in the form of a nozzle. The air outlet 23 extends in a direction essentially perpendicular to the longitudinal direction of the drive arm 3. From the inlet of the drive arm 3 (not shown in Figure 2), a primary airflow (L1) flows towards the air outlet 23. The primary airflow (L1) passes through the drive arm 3 with a primary flow rate (Dp) and a primary velocity (Vp). The ejector 5 is positioned around the air outlet opening 23 and at a certain distance from it. The ejector 5 has an inlet opening 51 and an outlet opening 52. The primary airflow (L1) flowing from the air outlet opening 23 is mixed with a secondary airflow (L2) flowing from the inlet opening 51 to the outlet opening 52.This secondary airflow (L2) has a secondary flow rate (Ds) and enters the inlet opening 51 at a secondary velocity (Vs), this secondary velocity (Vs) being lower than the primary velocity (Vp) of the primary airflow. From the outlet opening 52, a total airflow exits with a total flow rate (Dt), which is a mixture of the primary flow rate (Dp) and the secondary flow rate (Ds). The velocity of the total airflow from outlet 52 is the total velocity (Vt).

[0046] The ejector 5 is a device without moving parts, and therefore very reliable, which uses the viscosity of a high-speed airflow to entrain, by mixing, another airflow that is either slower-speed or at rest. Since these two airflows are intimately combined, they flow at a total velocity (Vt) lower than the primary velocity (Vp) of the primary airflow. This achieves the desired result, namely the reduction of energy lost during the emission of the air jet by the turbojet. As the amount of energy lost by The ratio to the thrust produced is expressed by the mathematical formula (Dt) x (Vt)² / 2 and is therefore proportional to (Dt) x (Vt). Increasing the flow rate (Dt) through the mixing of the primary flow (Dp) and the secondary flow (Ds) allows the thrust produced by the turbojet to be maintained. Consequently, the resulting technical effect is a reduction in the aircraft's specific fuel consumption.

[0047] Figure 3 schematically illustrates a rotor assembly 100 according to the invention. The rotor assembly 100 comprises a rotating element 110. A first blade 101 and a second blade 102 are connected to the rotating element 110. The blades 101 and 102 are adapted to rotate about their longitudinal axis so as to cyclically modify the angle of incidence of the blades 101, 102 during the rotation of the rotating element 110 about the axis of rotation 150. This modification of the angle of incidence is achieved by means of a swashplate, as is known in the prior art for helicopter blades.

[0048] The rotating element 110 is further provided with a first drive arm 103 and a second drive arm 104. The first drive arm 103 has an air inlet 113 and an air outlet 123. The first drive arm 103 is hollow and allows pressurized air to be conducted from the air inlet 113 to the air outlet 123. The air outlet 123 of the first drive arm 103 is substantially perpendicular to the longitudinal direction of the first drive arm 103. This means that the air flowing from the air inlet 113 of the first drive arm 103 exerts a reaction force on the first drive arm 103, near its end, in a direction perpendicular to the longitudinal direction of the first drive arm 103. Due to the existence of this reaction force, the rotating element 110 rotates in a direction opposite to the direction of the airflow exiting the air outlet opening 123.This rotation is schematically indicated by arrow 160 on [Fig.3].

[0049] The second drive arm 104 has an air inlet opening 114 and an air outlet opening 124. The second drive arm 104 is hollow and capable of conducting pressurized air from the inlet opening 114 to the air outlet opening 124. The air outlet opening 124 of the second drive arm 104 is substantially perpendicular to the longitudinal direction of the second drive arm 104. This means that the air flowing from the air inlet opening 114 of the second drive arm 104 exerts a reaction force on the second drive arm 104, near its end, in a direction perpendicular to the longitudinal direction of the second drive arm 104. Due to the existence of this reaction force, the rotating element 110 rotates in a direction opposite to the direction of the airflow from the air outlet opening 124. This rotation is shown schematically on [Fig.3] by arrow 160.

[0050] The drive arms 103, 104 are formed of two concentric conduits. Thus, the arms Engines 103 and 104 include an internal channel, for example tubular in shape, for conducting the primary airflow (L1). Engine arms 103 and 104 are provided with an external channel, for example aerodynamically shaped, for conducting the secondary airflow (L2).

[0051] As illustrated in [Fig.3], the air outlet opening 123 of the first motor arm 103 and the air outlet opening 124 of the second motor arm 104 are at an angle of approximately 180 degrees to each other.

[0052] According to the embodiment shown in [Fig. 3], the airflow enabling the rotation of the drive arms 103, 104 is generated by means of a turbojet 300. This turbojet has a rotation axis 301 which is aligned with the rotation axis 150 of the rotating element 110. The hot gas exiting the turbojet 300 is directed to an outlet opening 310. A connecting element 220, which is substantially Y-shaped, is connected to this outlet opening 310 by means of a swivel joint 320. The central arm of the connecting element 220 is connected to the outlet opening 310 of the turbojet 300. The upper arms of the connecting element 220 are connected to the inlet openings 113, 114 of the first and second drive arms 103, 104, respectively.

[0053] Thus, the use of the above-described structure of the rotor assembly 100 and, in particular, the alignment of the rotation axis 301 of the turbojet 300 with the rotation axis 150 of the rotating element 110, has the consequence that, when the motor arms 103 and 104 and the rotors 101 and 102 are set in rotation, no counter-torque or only a very limited counter-torque is generated in the direction opposite to the direction of rotation of the rotor assembly 100. This means that the rotor assembly 110 can, in principle, be used to create lift for a helicopter, without the helicopter having to be equipped with a tail rotor to neutralize the aforementioned counter-torque.

[0054] Figure 3 further shows that the air outlet opening 123 of the first drive arm 103 is equipped with an ejector 125. Similarly, the air outlet opening 124 of the second drive arm 104 is equipped with an ejector 126. The ejectors 125, 126 ensure that the hot primary airflow generated by the turbo-actuator 300 can mix with a secondary airflow near the air outlet openings 123, 124. The principle of mixing a primary airflow and a secondary airflow using an ejector is described above with reference to Figure 2.

[0055] In the embodiment shown in [Fig. 3], the inlets of ejectors 125 and 126 are connected to the inner side of drive arms 103 and 104, respectively. This means that the secondary airflow passing through ejectors 125 and 126 is drawn from inside drive arms 103 and 104. To allow this secondary airflow, the outer surface of drive arms 103 and 104 is provided with a perforated area 108. This perforated area 108 includes one or more openings for the passage of air for the flow Secondary airflow is directed from the outer surface of each of the engine arms 103, 104 towards the interior of the engine arms 103, 104. This secondary airflow contributes, firstly, to the operation of the ejectors 125, 126, as described above, and secondly, to improving the aerodynamic performance of the engine arms 103, 104, particularly by enhancing their lift-generating capacity. The ejector 125, 126 thus recovers the lost energy contained in the exhaust gases exiting through the air outlets 123, 124, and generates, within the engine arms 103, 104, a suction or vacuum used to draw in the secondary airflow. This aspect will be described below with reference to Figures 4 to 7.

[0056] It is noted that, according to an embodiment of the invention, not shown in the figures, the rotor assembly 100 comprises a single blade 101, 102, together with a single drive arm 103, 104. Said blade 101, 102 and said drive arm 103, 104 are, according to this embodiment, positioned in diametrically opposite directions (180°) with respect to the axis of rotation, the masses of the drive arm 103, 104 and of the blade 101, 102 mutually balancing each other. This embodiment has the advantage of significantly reducing the number of mechanical parts as well as the total mass, resulting in optimized performance and increased safety.

[0057] Figure 4 shows a top view of one possible embodiment of an arm Engine 103. The engine arm 103 has an air inlet 113 connected to the outlet of a turbojet 300 (as shown in [Fig. 3]). Inside the engine arm 103, pressurized air flows as a primary airflow with a flow rate (Dp) through a primary channel 106 to the air outlet 123. The air outlet 123 is equipped with an ejector 125 which provides a secondary airflow with a secondary flow rate (Ds), as described with reference to [Fig. 2].

[0058] The ejector 125 is connected to the inside of the drive arm 103. This means that the extension of the inlet opening 51 of the ejector 125 forms a secondary channel 107, which at least partially surrounds the primary channel 106. The secondary channel 107 is provided with a perforated area schematically indicated by reference number 108. The function of the perforated area 108 is to allow air to flow from outside the drive arm 103 into the secondary channel 107. For this purpose, the perforated area 108 is provided with one or more perforations or openings 109. According to the embodiment of [Fig. 4], the perforated area 109 comprises several openings that are substantially aligned. It is also possible to provide the perforated area 108 with a longitudinal opening. In addition, it is possible to provide openings arranged in the form of a plurality of bands, for example parallel, in the perforated area 108.

[0059] The air flowing along the outer surface of the drive arm 103 can flow from the outer surface of the drive arm 103 towards the inside of the drive arm 103, and by particular towards the secondary channel 107, through openings 109. The operation of these openings 109 and the effect of the flow of an air stream through these openings 109 on the aerodynamic properties of the engine arms 103, 104 are discussed above with reference to figures 6 and 7.

[0060] Figure 4 shows that the primary flow is guided inside the primary channel 106, which is positioned inside the secondary channel 107. The temperature of the gas flowing inside the primary channel 106 is relatively high, while the temperature of the air flowing inside the secondary channel 107 is relatively low. Consequently, heat exchange occurs between the gas and the air as the gas passes through the primary channel 106 and the air through the secondary channel 107, respectively.

[0061] Figure 4 shows that the total airflow from the ejector 125 is a mixture of the primary airflow through the primary channel 106 and the secondary airflow through the secondary channel 107. The primary airflow consists of the exhaust gases from the turbojet 300 (as shown in Figure 3). This primary airflow is extremely hot. The secondary airflow consists of ambient air. The temperature of the secondary airflow depends on the environment in which the device 100 is used. However, regardless of the environment, the secondary airflow is generally at a much lower temperature than the primary airflow.

[0062] As explained with reference to [Fig.2], the presence of an ejector 125 has the first technical effect of increasing the power of the motor arm 103.

[0063] The use of ejector 125 offers two further advantages resulting from the mixing of the hot primary airflow, which has a high velocity, and the secondary airflow, which has a relatively low temperature and velocity. These two advantages are to reduce, on the one hand, the infrared signature of the aircraft and, on the other hand, the noise generated by said aircraft.

[0064] Figure 5 shows the cross-section of the drive arm 103 as shown in Figure 4, near its free end, as shown in section AA. Figure 5 shows the primary channel 106, with the air outlet 123 at its end. The air outlet 123 is surrounded by the ejector 125, which forms the end of the secondary channel 107.

[0065] Figure 6 shows the cross-section of the drive arm 103 of Figure 4, according to section BB. The primary channel 106 is substantially cylindrical in shape. The secondary channel 107 is formed between the outer surface of the primary channel 106 and the inner wall 111 of the drive arm 103.

[0066] According to the embodiment shown in [Fig. 6], the drive arm 103 has a substantially aerodynamic cross-section with a pronounced positive angle of incidence. The drive arm 103 has an aerodynamic profile comprising an intrados and an extrados forming the transverse contour of the drive arm 103. The profile has an angle of incidence a constant positive pressure so that no delamination occurs on the lower surface.

[0067] Figure 6 also shows the airflow around the motor arm, the air circulating from From left to right in [Fig. 6]. On the outer surface of the drive arm 103, the perforated area 108 is schematically represented with one or more openings. [Fig. 6] shows the airflow around the drive arm 103 in the case where no air is drawn in through the perforated area 108.

[0068] As shown in [Fig. 6], the airflow flows from a leading edge 180 on the outer surface of the drive arm 103 to a point 181 where the boundary layer separates and can no longer follow the surface of the drive arm 103. The separation of the boundary layer results in a considerable reduction in lift and an increase in drag. Conversely, thanks to the positive angle of attack, the lower surface does not separate. On the right side of the drive arm 103 in [Fig. 6] is a zone of turbulent air 135.

[0069] Fig. 7 shows the cross-section of the drive arm 103 according to Fig. 6.

[0070] Figure 7 schematically shows the airflow over the surface of the arm motor 103 when air is drawn through the perforated area 108.

[0071] Insofar as air is drawn in through the opening 109 of the perforated area 108, the boundary layer of the air flowing along the upper surface of the motor arm 103 can follow the surface of the motor arm 103 for an extended period. Consequently, the air intake through the perforated area 108 delays or even prevents the point at which the boundary layer separates from the upper surface of the motor arm 103.

[0072] A comparison between figures 6 and 7 shows that the aspiration of air through the perforated area 108 makes it possible to use a very high-lift profile at high angle of attack without causing separation of the boundary layer on the upper surface, which provides considerable lift to the driving arms 103, 104.

[0073] Furthermore, it can be seen on [Fig.7] that the dimension of the turbulent air zone 135 is reduced when air is drawn through the perforated zone 108.

[0074] Thus, the use of ejectors 125, 126 in combination with the aspiration of an airflow through the perforated area 108 makes it possible to improve the dynamic properties of the engine arm 103 and to create efficient lift using the engine arms 103, 104, which improves the ratio between fuel consumption and lift produced.

[0075] The technical effects obtained through the presence of the ejectors and the perforated area, as mentioned above, are as follows:

[0076] - the increase in torque supplied by drive arms 103, 104 driving the rotor;

[0077] - reducing the aircraft's fuel consumption;

[0078] - the increase in the lift of the drive arms 103, 104;

[0079] - the reduction of air jet noise;

[0080] - the reduction of the infrared signature of the device. Examples

[0081] According to one embodiment of the invention, the rotating element 110 comprises drive arms 103 and 104. The turbojet 300 generates an airflow that rotates the rotating element. Thus, thanks to the presence of the ejectors 125 and 126 and the suction of air through the perforated area 108 of the drive arms 103 and 104 respectively, the two drive arms 103 and 104 can be used to create additional lift during rotation by suction of the boundary layer.

[0082] The single-blade / single-engine arm configuration according to one embodiment of the invention optimizes the concept by improving the payload that can be transported and / or the distance traveled. Indeed, the single blade must be longer than the blade of the two-bladed rotor, which improves lift by relatively reducing the losses induced at the blade tip. This configuration is simpler and lighter due to a simplified pitch-change mechanism and the elimination of one blade and one engine arm, and it improves the lift of the engine arm compared to the sum of the two arms' lift. This improved lift is due to a higher boundary layer intake airflow, as the secondary flow of the single nozzle can be twice that of a nozzle on the dual engine arm.

Claims

Claims

1. A rotor assembly (100) for a helicopter comprising a rotating element (110) adapted to rotate about an axis of rotation (150), wherein the rotor assembly (100) comprises: - at least one blade (101, 102) fixed to said rotating element (110), the angle of incidence of said at least one blade (101, 102) being adjustable upon rotation of said at least one blade (101, 102) about the axis of rotation (150), - at least one motor arm (103, 104) comprising, on the one hand, a first end connected to the rotating element (110) and an air inlet opening (113, 114) located near said first end, and on the other hand, a second free end and an air outlet opening (123, 124) located near said second free end, said at least one motor arm (103, 104) being adapted to guide an air flow from said air inlet opening (113, 114) to said air outlet opening (123, 124),said rotor assembly (100) being characterized in that said at least one motor arm (103, 104) is provided with an ejector (50, 125, 126), said ejector (50, 125, 126) being positioned circumferentially around the air outlet opening (123, 124) of said at least one motor arm (103, 104) and at a determined distance from the air outlet opening (123, 124) of said at least one motor arm (103, 104), said ejector (50, 125, 126) comprising an inlet opening (51) and an outlet opening (52), a primary air flow (Lp) flowing at a primary flow rate (Dp) from the air inlet opening (113, 114) to the air outlet opening (123, 124) of said at least one motor arm (103, 104) and a secondary air flow (Ls) flowing at a secondary flow rate (Ds) from the inlet opening (51) to the outlet opening (52) through the ejector (50, 125, 126),to form a total air flow (Lt) comprising a total flow rate (Dt) equal to the sum of the primary flow rate (Dp) and the secondary flow rate (Ds).,

2. Rotor assembly (100) according to claim 1, wherein said at least one motor arm (103, 104) comprises a primary channel (106), for example of tubular shape, for conducting the primary air flow (L1) from the air inlet opening (113, 114) to the air outlet opening (123, 124).

3. A rotor assembly (100) according to claim 1 or 2, wherein said at least one motor arm (103, 104) comprises a secondary channel (107) and a perforated area (108) to allow the passage of air from the outside of said at least one motor arm (103, 104) towards the inside of said secondary channel (107) and of said at least one motor arm (103, 104), the perforated zone (108) extending in the longitudinal direction of said at least one motor arm (103, 104).

4. A rotor assembly (100) according to claim 3, wherein the perforated area (108) is provided with one or more perforations (109).

5. A rotor assembly (100) according to claim 4, wherein the perforations (109) are arranged substantially in line.

6. A rotor assembly (100) according to claim 5, wherein the perforations (109) are arranged in two or more substantially parallel bands.

7. A rotor assembly (100) according to any one of claims 3 to 6, wherein the inner face of the perforated area (108) is connected to the inlet opening (51) of the ejector (50, 125, 126) by said secondary channel (107).

8. A rotor assembly (100) according to any preceding claim, wherein said at least one motor arm (103, 104) has a substantially aerodynamically shaped cross-section.

9. Rotor assembly (100) according to claim 8, wherein said at least one motor arm (103, 104) has an aerodynamic profile comprising a lower surface and an upper surface forming the transverse contour of said at least one motor arm (103, 104).

10. A helicopter provided with a rotor assembly (100) according to any one of claims 1 to 9.

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