CN112896503B

CN112896503B - Helicopter rotor blade capable of restraining tip vortex of blade

Info

Publication number: CN112896503B
Application number: CN202110291176.7A
Authority: CN
Inventors: 林麒; 陈晨; 张涛; 刘汝兵
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2021-03-18
Filing date: 2021-03-18
Publication date: 2022-12-13
Anticipated expiration: 2041-03-18
Also published as: CN112896503A

Abstract

The application discloses a helicopter rotor blade capable of inhibiting tip vortex, which comprises a blade body and at least one plasma jet generator; the plasma jet generator is embedded in the blade body and jets plasma jet through jet holes corresponding to the plasma jet generator and opened in the end face of the blade tip. By adopting the technical scheme, the blade tip vortex can be effectively inhibited, and the blade-vortex noise is reduced. Furthermore, the blade tip end face is constructed into a wave shape by utilizing bionics, and the position of the jet hole is arranged at the top end of the wave crest, so that blade tip vortex is more effectively inhibited through a main way and a passive way, and blade-vortex interference noise is more obviously reduced.

Description

Helicopter rotor blade capable of restraining tip vortex of blade

Technical Field

The application relates to the field of helicopters, in particular to a helicopter rotor blade capable of restraining blade tip vortexes.

Background

The helicopter has the unique performances of vertical take-off and landing, hovering, low-altitude low-speed flight and the like, so that the helicopter is increasingly applied to the fields of national defense and civil use. However, the helicopter has the defect of excessive noise, so that the stealth of the helicopter is insufficient in military, the track is easily exposed too early, and the battlefield defense and the survival capability of the helicopter are greatly influenced; in the civil aspect, the excessive noise not only affects the riding comfort of passengers, but also causes serious noise pollution, and does not meet the requirement of environmental protection.

Helicopter noise is primarily derived from aerodynamic noise of the helicopter rotor blades, which is generated by unsteady air flows caused by the interaction of the air with the helicopter rotor blades rotating at high speed. Research shows that the paddle-vortex interference phenomenon is one of main factors for generating aerodynamic noise, and is a physical interference phenomenon which is specific to a helicopter and is formed by collision of a rotating blade and a tip vortex of a front blade which falls off.

The invention patent application with publication number CN106741922 discloses a rotor noise suppression method, which is based on the principle that the airflow at the front edge of a rotor blade is guided to a blade tip in a manner of forming a hole at the front edge of the blade tip, so that the airflow is emitted perpendicularly to the end surface of the blade tip, and the strength of a blade tip vortex is weakened, thereby achieving the effect of reducing the interference noise of the blade-vortex. However, this method changes the tip airflow, increases flow losses, and reduces tip efficiency.

Disclosure of Invention

An object of the present application is to overcome the above-mentioned drawbacks or problems in the background art and to provide a helicopter rotor blade capable of suppressing the tip vortex of the blade, which can effectively suppress the tip vortex of the blade and reduce the blade-vortex noise.

In order to achieve the purpose, the following technical scheme is adopted:

a helicopter rotor blade capable of suppressing tip vortices, said helicopter rotor blade rotating about a rotational axis, characterized by comprising a blade body and at least one plasma jet generator; the plasma jet generator is embedded in the blade body, the blade body is provided with jet holes which are equal to the plasma jet generator in number and correspond to the plasma jet generator in number one by one, and openings of the jet holes are distributed along a first direction from the front edge to the rear edge; one end of each jet hole is communicated with the corresponding plasma jet generator, and the other end of each jet hole is opened at the end face of the blade tip so as to jet plasma jet along the span direction of the blade body.

Further, the plasma jet generator comprises a generator body and two electrodes; the generator body is embedded in the paddle body and is provided with a plasma generation cavity communicated with the jet hole; the two electrodes are externally connected with a power supply capable of generating pulse voltage and respectively extend into the plasma generating cavity.

Further, the extending direction of the jet hole is the same as the extending direction of the blade body.

Furthermore, if an intersection line exists between the end face of the blade tip and any plane passing through the rotating shaft, the intersection line is a line segment or a smooth curve.

Further, any one of the intersecting lines is a line segment parallel to the rotation axis.

Further, the number of the plasma jet generators is four.

Further, a first projection of the tip end surface on a plane perpendicular to the rotation axis is wavy in a first direction.

Further, the first projection comprises at least one wave crest and a wave trough which are alternately arranged, the number of the jet holes is equal to that of the wave crests, and the openings of the jet holes are correspondingly arranged at the top end, farthest from the rotating shaft, of the wave crest.

Further, the first projection includes four peaks and three valleys alternately arranged.

Compared with the prior art, the scheme has the following beneficial effects:

the end face of the blade tip is provided with a jet hole for jetting plasma jet, and the jet hole has an interference effect on the formation of the blade tip vortex. On one hand, the speed of the tip end face of the blade is reduced, so that the value of the tip end face vortex is reduced to inhibit the strength of the tip vortex at the trailing edge of the blade tip; on the other hand, the jet flow inhibits the formation and development of the tip vortex at the rear edge of the tip by inhibiting the formation and development of the tip end surface and the vortex above the tip, so that the tip vortex can be effectively inhibited, and the interference noise of the blade-vortex is reduced.

The intersection line of the end face of the blade tip and any plane passing through the rotating shaft is a line segment or a smooth curve, so that the end face of the blade tip does not change suddenly in the thickness direction, the wavy structure is integrated with the blade body, and the structural strength of the blade tip cannot be reduced.

The first projection of the blade tip end face on the plane perpendicular to the rotating shaft is in a wave shape along the first direction, the opening of the jet hole is arranged at the top end of the wave crest, the bionic principle is fully utilized, blade tip vortexes are more effectively inhibited through a main path and a passive path, the strength of the blade tip vortexes is weakened, and therefore blade-vortex interference noise is more remarkably reduced.

Drawings

In order to more clearly illustrate the technical solution of the embodiments, the drawings needed to be used are briefly described as follows:

FIG. 1 is a partial top view of a rotor blade for a helicopter in accordance with a first embodiment;

FIG. 2 is a front view of a rotor blade according to one embodiment of the present invention;

FIG. 3 is an enlarged partial sectional view of portion A of FIG. 1;

FIG. 4 is a partial top view of a rotor blade according to a second embodiment of the present invention;

FIG. 5 is a front view of a rotor blade of a helicopter according to a second embodiment;

FIG. 6 is an enlarged partial cross-sectional view of portion B of FIG. 4;

FIG. 7 is a top view of a helicopter rotor blade according to the comparative example;

FIG. 8 is a front view of a helicopter rotor blade according to a comparative example;

FIG. 9 is a top view of a helicopter rotor blade according to a comparative example;

FIG. 10 is a front view of a helicopter rotor blade according to a comparative example;

FIG. 11 is a schematic view of the tip vortex cross-sectional location;

FIG. 12 is a schematic sectional view of a tip vortex of a comparative example I;

FIG. 13 is a schematic cross-sectional view of a tip vortex according to the first embodiment;

FIG. 14 is a schematic tip vortex cross-sectional view of a comparative example;

FIG. 15 is a schematic cross-sectional view of the tip vortex of the second embodiment;

FIG. 16 is a blade tip vortex tangential velocity distribution diagram in the X-axis direction at a cross section for each simulation calculation example;

fig. 17 is a schematic view of the rotational angular velocity of the tip vortex core of each simulation calculation example.

Description of the main reference numerals:

a helicopter rotor blade 1; a blade body 2; a leading edge 3; a trailing edge 4; a tip end face 5; a plasma jet generator 6, a generator body 61, a plasma generating cavity 62 and an electrode 63; a jet hole 7; an incoming flow V; plasma jet V _j (ii) a Blade tip vortex core cross section flow velocity V _x (ii) a Maximum flow velocity V of cross section of vortex core of tip vortex of propeller _xmax (ii) a A chord length c; a first plane P.

Detailed Description

In the claims and specification, unless otherwise specified the terms "first", "second" or "third", etc., are used to distinguish between different items and are not used to describe a particular order.

In the claims and specification, unless otherwise limited, the terms "central," "transverse," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," "counterclockwise," and the like are used in a generic sense only to identify certain features of the device or element, and not to identify particular features of the device or element.

In the claims and the specification, unless otherwise defined, the terms "fixedly" or "fixedly connected" are to be understood in a broad sense as meaning any connection which is not in a relative rotational or translational relationship, i.e. including non-detachably fixed connection, integrally connected and fixedly connected by other means or elements.

In the claims and specification, unless otherwise defined, the terms "comprising", "having" and variations thereof mean "including but not limited to".

In the claims and in the description, unless otherwise defined, the term "undulated" means that the first projection comprises at least one peak and at least one valley arranged alternately in the first direction, the peak being further away from the axis of rotation than the valley. The distance from the top end of the wave crest to the rotating shaft is gradually increased along the first direction, and the distance from the top end of the wave crest to the rotating shaft is gradually decreased along the first direction. The bottom end of the wave trough is closest to the rotating shaft, the distance from the starting point of the wave trough to the bottom end of the wave trough to the rotating shaft is gradually reduced along the first direction, and the distance from the bottom end to the terminal point of the wave trough to the rotating shaft is gradually increased.

The technical solution in the embodiments will be clearly and completely described below with reference to the accompanying drawings.

Example one

Referring to fig. 1, 2 and 3, fig. 1, 2 and 3 show a helicopter rotor blade 1 according to a first embodiment, the helicopter rotor blade 1 being rotatable about an axis of rotation. As shown, a helicopter rotor blade 1 comprises a blade body 2 and four plasma jet generators 6.

In this embodiment, the blade body 2 is Clark YH wing with a chord length of 150mm. The blade body 2 is provided with a front edge 3, a rear edge 4 and a tip end surface 5 positioned between the front edge and the rear edge, in the embodiment, the tip end surface 5 is perpendicular to the span direction of the blade body 2, so if an intersection line exists between the tip end surface 5 and any plane passing through the rotating shaft, the intersection line is a line segment parallel to the rotating shaft. In other embodiments, the intersection may be non-parallel to the axis of rotation or may be smoothly curved.

The blade body 2 is provided with four jet holes 7 corresponding to the four plasma generators 6 one by one. As shown in fig. 2, the four jet holes 7 are arranged in a first direction from the leading edge 3 to the trailing edge 4, which in the present embodiment is parallel to the chord length direction of the blade body 2. One end of each jet hole 7 is communicated with the corresponding plasma jet generator 6, the other end of each jet hole is opened at the tip end face 5 and is positioned at a position close to the lower surface of the blade, and the diameter of each opening is 2mm. The extension direction of the jet hole 7 is the same as the span direction of the blade tip body 2, namely, the jet hole is vertical to the blade tip end surface 5. The distance between the axes of the adjacent jet holes 7 is 40mm, the distance between the axis of the jet hole 7 closest to the front edge 3 and the front edge 3 is 15mm, and the distance between the axis of the jet hole 7 closest to the rear edge 4 and the rear edge 4 is 15mm.

As shown in fig. 3, each plasma jet device 6 includes a generator body 61 and two electrodes 63. The generator body 61 is made of a high-temperature-resistant insulating material, is embedded in the blade body 2, and is provided with a plasma generation chamber 62 communicated with the corresponding jet hole 7. The two electrodes 63 have different polarities and may be made of tungsten-copper alloy. The two electrodes 63 are respectively externally connected with a power supply capable of generating pulse voltage and respectively extend into the plasma generating chamber 62. The ends of the two electrodes 63 that extend into the plasma-generating chamber 62 are spaced apart by a distance that is determined based on the parameters associated with the power supply. The electrode 63 and the generator body 61 are fixed by high temperature resistant silica gel. The power supply is used for generating a pulsed excitation voltage, and in the present embodiment, four plasma generators 6 share one power supply. After voltage is applied, air between the two electrodes 63 can be highly ionized to form plasma and generate expansion, and the plasma passes through the jet hole 7 communicated with the plasma generation cavity 62 and along the bladeSpanwise projecting plasma jet V of the body 2 _j . When the voltage value is zero, the gas flow flows into the plasma generation chamber 62 from the outside through the jet hole 7 due to the negative pressure formed in the plasma generation chamber 62.

Example two

Referring to fig. 4, 5 and 6, fig. 4, 5 and 6 show a helicopter rotor blade 1 according to a second embodiment. As shown, the helicopter rotor blade 1 of the second embodiment differs from the helicopter rotor blade of the first embodiment by:

a first projection of the tip end surface 5 of the blade body 2 in the second embodiment on a plane perpendicular to the rotation axis is waved in the first direction. The first projection comprises four wave crests and three wave troughs which are alternately arranged and smoothly transited, the distance between every two adjacent wave crests is the wavelength, the wavelength is 40mm in the embodiment, the distance between the bottom end, closest to the rotating shaft, of each wave trough and the top end, farthest from the rotating shaft, of each wave crest along the extending direction of the blade body 2 is the amplitude, and the amplitude in the embodiment is 9mm; the distance from the top of the peak closest to the leading edge 3 to the leading edge in the chord length direction is 15mm, and the distance from the top of the peak closest to the trailing edge 4 to the trailing edge in the chord length direction is 15mm. Therefore, the openings of the four jet holes 7 are respectively positioned at the topmost ends of the four wave crests.

In the embodiment, the blade tip part of the blade body is uniform in the thickness direction, the wavy structure is integrated with the blade body, and the structural strength of the blade tip is not reduced.

In order to verify the effect of the first embodiment and the second embodiment on inhibiting the tip vortex, simulation calculation was also performed on the first embodiment and the second embodiment as well as the first comparative example and the second comparative example. The blade tip vortex suppression effect can be evaluated from three dimensions of a blade tip vortex central vortex value, a vortex core diameter of a blade tip vortex and a rotation angular velocity of a blade tip vortex core. The ratio of the central vortex volume value of the tip vortex in the embodiment is smaller, the ratio of the vortex core diameter of the tip vortex is larger, the ratio of the rotation angular velocity of the tip vortex core is smaller, and the inhibition effect of the tip vortex is better.

Comparative example 1

Referring to fig. 7 and 8, the comparative example one differs from the example one in that there are no four plasma ejectors 6, and there are no four ejection holes 7 on the blade body 2. Therefore, the first comparative example can examine the tip vortex suppression effect of the first example relative to the first comparative example. Comparative example one the tip vortex suppression effect of the two comparative examples versus comparative example one can also be examined.

Comparative example No. two

Referring to fig. 9 and 10, the comparative example b is different from the example b in that there are no four plasma ejectors 6 and no four ejection holes 7 on the blade body 2. Thus, the tip vortex suppression effect of the two comparative examples can be examined compared to the two comparative examples. The second comparative example also serves as a comparison of the tip vortex suppression effect of the first example.

In the simulation calculations of the first comparative example, the first example, the second comparative example and the second example, the incoming flow V is parallel to the chord length direction of the helicopter, i.e. perpendicular to the span direction of the blade body 2. The incoming flow V velocity is 100 m/s.

Through simulation calculation, as shown in fig. 11, on a first plane P perpendicular to the incoming flow direction at a position of a chord length behind the blade body 2, the section of the tip vortex of the blade in the first comparative example is shown in fig. 12, the section of the tip vortex of the blade in the first comparative example is shown in fig. 13, the section of the tip vortex of the blade in the second comparative example is shown in fig. 14, and the section of the tip vortex of the blade in the second example is shown in fig. 15. It is apparent that the tip vortex center vortex value of the comparative example one is the largest, the tip vortex center vortex value of the example two is the smallest, which is about 30% of the tip vortex center vortex value of the comparative example one, and the tip vortex center vortex value of the example one is smaller than the tip vortex center vortex value of the comparative example one and larger than the tip vortex center vortex value of the comparative example two.

Fig. 16 shows the tip vortex core cross-sectional flow velocity V in the X-axis direction parallel to the span direction of the blade body 2 on the first plane P _x . As shown in fig. 16, the tip vortex core diameter of the first comparative example was 29.4mm, the tip vortex core lift of the first example was 35.4mm, the tip vortex core diameter of the first comparative example was 44.5mm, and the tip vortex core diameter of the second example was 74.1mm. It can be seen that the tip vortex core of the first example is the smallest and smallest diameter, while the tip vortex core of the second example is the largest in vertical liftAlso, the tip vortex core diameter of example one is larger than that of comparative example one and smaller than that of comparative example two.

FIG. 16 also shows the tip vortex core cross-sectional flow velocity V of the four simulation calculations _x And the maximum flow velocity of the cross section of the tip vortex core is V _xmax . Wherein V of comparative example I _xmax 44.8m/s, V of example one _xmax V of 42.9m/s, comparative example one _xmax 31.2m/s, V of example two _xmax Is 29m/s. Thus, V of the first embodiment _xmax V relative to comparative example one _xmax Reduced by 4.7%, V of comparative example II _xmax V relative to comparative example one _xmax The V of example two is reduced by 30.2 percent _xmax V relative to comparative example one _xmax The reduction is 35.1%.

FIG. 17 shows the tip vortex core rotational angular velocities for four simulated calculated examples. As shown in fig. 17, the rotational angular velocity of the tip vortex core of the first comparative example is 3048rad/s, the rotational angular velocity of the tip vortex core of the first example is 2424rad/s, the rotational angular velocity of the tip vortex core of the second comparative example is 1402rad/s, and the rotational angular velocity of the tip vortex core of the second example is 782rad/s.

From the comparison of the above four simulation calculation examples, it can be known that the jet holes 7 formed in the blade tip end surface 5 jet the plasma jet, which has an interference effect on the formation of the blade tip vortex. On the one hand the plasma jet V _j The speed of the tip end face of the blade tip is reduced, so that the value of the tip end face vortex is reduced to inhibit the strength of the tip vortex at the trailing edge of the blade tip; plasma jet V on the other hand _j The formation and development of the tip vortex at the trailing edge of the tip are inhibited by inhibiting the formation and development of the tip end surface 5 and the vortex above, so that the tip vortex can be effectively inhibited, and the interference noise of the blade-vortex is reduced.

The blade tip end face 5 is in a wave shape, the jet hole 7 is formed in the top end of the wave crest of the blade tip end face 5 to jet plasma jet, the bionic principle can be fully utilized, blade tip vortex can be effectively restrained through a main way and a passive way, the strength of the blade tip vortex is further limited, and therefore blade-vortex interference noise is reduced more remarkably.

The description of the above specification and examples is intended to be illustrative of the scope of the present application and is not intended to be limiting.

Claims

1. A helicopter rotor blade capable of suppressing tip vortices, said helicopter rotor blade rotating about a rotational axis, characterized by comprising a blade body and at least one plasma jet generator; the plasma jet generator is embedded in the blade body, the blade body is provided with jet holes which are equal to the plasma jet generator in number and correspond to the plasma jet generator in number one by one, and openings of the jet holes are distributed along a first direction from the front edge to the rear edge; one end of each jet hole is communicated with the corresponding plasma jet generator, and the other end of each jet hole is opened on the end face of the blade tip so as to jet plasma jet along the span direction of the blade body.

2. A helicopter rotor blade according to claim 1 wherein said plasma jet generator comprises a generator body and two electrodes; the generator body is embedded in the paddle body and is provided with a plasma generation cavity communicated with the jet hole; the two electrodes are externally connected with a power supply capable of generating pulse voltage and respectively extend into the plasma generating cavity.

3. A helicopter rotor blade according to claim 1 wherein said jet holes extend in the same direction as the span-wise direction of said blade body.

4. A helicopter rotor blade according to claim 1 wherein the intersection of said tip end surface with any plane passing through said axis of rotation is a line segment or a smooth curve if any.

5. A helicopter rotor blade according to claim 4, wherein any said intersection line is a line segment parallel to said axis of rotation.

6. A helicopter rotor blade capable of suppressing tip vortices according to claim 1 wherein said plasma jet generators are four in number.

7. A helicopter rotor blade according to any of claims 1 to 5 wherein a first projection of said tip end surface onto a plane perpendicular to said axis of rotation is undulating in a first direction.

8. The helicopter rotor blade according to claim 7 wherein said first projection comprises at least one peak and one valley arranged in an alternating pattern, said plurality of jet holes being equal to said number of peaks and said openings of each jet hole opening in a one-to-one correspondence at the top of said peak furthest from said axis of rotation.

9. A helicopter rotor blade according to claim 8 wherein said first projection comprises four peaks and three valleys in an alternating pattern.