CN214084760U

CN214084760U - Helicopter blade capable of restraining tip vortex of blade

Info

Publication number: CN214084760U
Application number: CN202120027338.1U
Authority: CN
Inventors: 林麒; 陈晨; 张涛; 陶逸萌; 刘汝兵
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2021-01-06
Filing date: 2021-01-06
Publication date: 2021-08-31
Anticipated expiration: 2031-01-06

Abstract

The application discloses a helicopter blade capable of inhibiting tip vortex, which utilizes the bionics principle to design the outer edge of the tip of the helicopter blade into a wave shape, a wavy shape, a sawtooth shape or a feather tip shape along the direction from a front edge to a rear edge, does not need to add a mechanical structure, and can effectively inhibit the tip vortex interference without injecting extra energy.

Description

Helicopter blade capable of restraining tip vortex of blade

Technical Field

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

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 mainly derived from aerodynamic noise of the helicopter blades, which is generated by unsteady movements and flows caused by the interaction of the air with the helicopter blades rotating at high speed. Research has shown that the paddle-vortex interference phenomenon is one of the major factors in generating aerodynamic noise. The paddle-vortex interference phenomenon is a physical interference phenomenon peculiar to a helicopter, which is formed by collision of a rotating blade and a tip vortex of a blade falling off from the front blade.

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 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 the vortex of the blade tip is weakened, so as to achieve the effect of reducing the interference noise of the blade-vortex. The method changes the airflow flow of the blade tip, increases the flow loss and reduces the blade tip efficiency.

The invention patent with publication number CN108216617B discloses a method for suppressing interference noise of helicopter blade-vortex, which is based on the principle that at least one synthetic jet generator is arranged at a proper position of the blade tip from the end surface, and the synthetic jet generator generates a synthetic jet which is backward and downward relative to the front direction of the blade on the lower surface of the blade tip near the trailing edge to weaken the strength of the blade tip vortex and change the falling direction thereof, so as to avoid the blade tip vortex from interfering with the subsequent blade, and achieve the effect of suppressing the interference noise of the blade-vortex. But this method requires the injection of additional energy, such as electrical energy.

SUMMERY OF THE UTILITY MODEL

The present application aims to overcome the above-mentioned defects or problems in the background art, and provides a helicopter blade capable of suppressing the tip vortex of a blade, which does not require the addition of a mechanical structure, and can effectively suppress the tip vortex of a blade without injecting additional energy.

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

a helicopter blade capable of suppressing tip vortex, said helicopter blade rotating about a first axis with a tip formed at a free end thereof, a first projection of an outer edge of said tip formed on a plane perpendicular to said first axis being in the shape of a wave, undulation, sawtooth or plume in a first direction from a leading edge of said helicopter blade to a trailing edge of said helicopter blade.

Preferably, if there is an intersection line between the outer edge of the tip and any plane of the first axis, the intersection line should be a line segment or a smooth curve.

Preferably, when the first projection is waved along the first direction, the first projection includes four peaks and three troughs which are alternately arranged and smoothly transited, and the peaks are farther from the first axis than the troughs.

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

as shown in FIG. 1, a rotating blade may generate a tip vortex F at the tip of the blade₁，Г₁The vortex line formed by the extension development of the blade falls backwards and interacts with the subsequent blade to generate blade-vortex interference noise. The invention utilizes the principle of bionics to design the plane-shaped oar tip shown in figure 1 into a feather-like (comprising a wavy shape, a sawtooth shape or a feather tip shape), and the feather-like oar tip can effectively reduce the oar tip vortex reverse₁The size of the blade tip vortex is reduced, the falling direction of the blade tip vortex can be changed, the falling blade tip vortex is far away from the following blade as far as possible, the interference of the blade vortex is avoided or weakened, and the noise is reduced. The invention can not only inhibit the tip vortex of the paddle and reduce the interference noise of the paddle-vortex without adding a mechanical structure and injecting extra energy, but also is easy to design and manufacture and can not increase the weight of the paddle.

In a preferred embodiment, the intersection of the outer edge of the tip with the plane of the first axis is a line segment or a smooth curve, so that even if the outer edge of the tip is wavy, undulating, serrated or feather-like in the first direction, it is elongated in the length direction of the blade in the thickness direction and is integral with the helicopter blade, so that the structural strength of the tip is not 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 schematic view of tip vortex formation;

FIG. 2 is a top plan view of a tip portion of a blade for a helicopter in accordance with a first embodiment;

FIG. 3 is a top plan view of a tip portion of a blade for a second embodiment of the helicopter;

FIG. 4 is a top plan view of a tip portion of a blade of a third embodiment of the helicopter;

FIG. 5 is a top plan view of a tip portion of a blade of a helicopter of an embodiment four;

FIG. 6 is a schematic view of tip vortex in the first embodiment.

FIG. 7 is a schematic view of a tip vortex in a prior art blade.

Description of the main reference numerals:

helicopter blade 1, leading edge 2, trailing edge 3, tip 4, crest 6, trough 7, peak 8, lowest point 9, repeating unit 10, start of first projection 11, end of first projection 12, first direction (incoming flow direction) V.

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 specified, the terms "central," "lateral," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," "counterclockwise," and the like are used in the orientation and positional relationship indicated in the drawings and are used for ease of description only and do not imply that the referenced device or element must have a particular orientation or be constructed and operated in a particular orientation.

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 in an alternating and smooth transition along the first direction, the peak being further away from the first axis than the valley. The peak is a smooth curve and has a highest point located in the middle of the peak, the highest point is farthest from the first axis, the distance from the starting point of the peak to the highest point and the first axis gradually increases along the first direction, and the distance from the highest point to the terminal point of the peak and the first axis gradually decreases. The trough is a smooth curve having a lowest point located in the middle of the trough, the lowest point being closest to the first axis, the distance from the starting point of the trough to the lowest point along the first direction gradually decreasing, and the distance from the lowest point to the ending point of the trough to the first axis gradually increasing. The distance between two adjacent wave crests in the first direction is the wavelength, and the difference value between the distance between the highest point of the wave crest and the first axis and the distance between the lowest point of the wave trough and the first axis in the adjacent wave crests and wave troughs is the wave height.

In the claims and the description, unless otherwise specified, the term "relief" means that the first projection has a highest point which is the farthest from the first axis, and that the distance from the start of said first projection to the highest point from said first axis increases progressively in the first direction; along the first direction, the distance from the highest point to the terminal point of the first projection and the first axis is gradually reduced.

In the claims and the description, unless otherwise specified, the term "zigzag" means that the first projection comprises at least two repeating units distributed along the first direction, each repeating unit being formed by at least two line segments connected in series, each repeating unit further comprising at least one lowest point closest to the first axis and at least one highest point farthest from the first axis.

In the claims and in the description, unless otherwise defined, the term "pinnate" means that the first projection includes at least two repeating units distributed along a first direction, each repeating unit including at least one curve that has a non-smooth transition with the curve or line segment to which it is connected. Each repeating unit further includes at least one nadir nearest the first axis and at least one apex farthest from the first axis.

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

Referring to fig. 2, fig. 2 shows a tip portion of a helicopter blade 1 according to a first embodiment. As shown in fig. 2, the helicopter blade 1 rotates about a first axis such that the leading edge 2 of the helicopter blade 1 is facing the wind and the trailing edge 3 of the helicopter blade 1 is facing the wind. A first direction V, also the incoming flow direction V, from the leading edge 2 of the helicopter blade 1 to the trailing edge 3 of the helicopter blade 1. The free end of the helicopter blade 1 forms a tip 4. The outer edge of the tip 4 forms a first projection on a plane perpendicular to the first axis. In fig. 2, the first projection is the portion of the helicopter blade in fig. 2 remaining after the removal of the leading edge 2 and the trailing edge 3 from the outer edge line. As shown in fig. 2, in the present embodiment, the first projection is waved along the first direction V, and has four peaks 6 and three troughs 7 which are alternately arranged and smoothly transited, and the peaks 6 are farther from the first axis than the troughs 7. If there is an intersection line between the outer edge of the blade tip 4 and any plane of the first axis, the intersection line is a line segment in the present embodiment, and may be a smooth curve in other embodiments. This means that the wave-like structure in the tip 4 is integral with the helicopter blade 1 in the thickness direction, rather than an attachment structure, which does not reduce the structural strength of the tip 4, and is also easy to design and manufacture without increasing the weight of the helicopter blade 1.

Specifically, the helicopter blade 1 in the present embodiment is used as a model, and the chord length of the helicopter blade 1 is set to 150 mm, the span length is set to 381 mm, and the wave of the first projection of the outer edge of the tip 4 is set to 9 mm in wavelength and 7 mm in wave height. The blade tip vortex shape and the vortex quantity isoline at a chord length position downstream of the blade tip trailing edge obtained by calculation simulation under the condition that the incoming flow Mach number is 0.3 are shown in FIG. 6. Fig. 7 is a blade tip vortex shape and vortex quantity contour line at a chord length downstream of the blade tip trailing edge, which are obtained by computational simulation under the same incoming flow condition without using the model of the outer edge of the blade tip 4 in the prior art. As can be seen by comparison, the tip vortex in fig. 6 is more relaxed than the tip vortex in fig. 7, with a large range (the vorticity is dispersed), and the vorticity value at the vortex core is reduced, and with a large range, which indicates that the tip vortex strength in fig. 6 is weaker than that in fig. 7, specifically, the tip vortex amount is reduced by 30-50%. And the core positions of the tip vortex cores in the two figures are different. Therefore, the helicopter blade 1 in the first embodiment adopts the new outer edge of the blade tip 4, so that the strength of the blade tip vortex is obviously reduced, and the shedding direction of the blade tip vortex is changed. Therefore, the helicopter blade 1 in the embodiment can suppress the blade tip vortex without adding a mechanical structure or injecting extra energy, thereby reducing the blade-vortex interference noise.

Fig. 3, 4 and 5 show the tip portions of the helicopter blade 1 in the second, third and fourth embodiments, respectively. As shown in fig. 3, in the second embodiment, the first projection formed by the outer edge of the blade tip 4 is undulated along the first direction, and has a highest point 8 farthest along the first axis, along the first direction, the distance from the starting point 11 to the highest point 8 of the first projection to the first axis gradually increases, and the distance from the highest point 8 to the end point 12 of the first projection to the first axis gradually decreases. As shown in fig. 4, the first projection formed by the outer edge of the blade tip 4 in the third embodiment is zigzag along the first direction, and in the third embodiment, the first projection has seven repeating units 10 distributed along the first direction, each repeating unit 10 is formed by two connected line segments and includes a highest point 8 farthest from the first axis and two lowest points 9 closest to the first axis and located at two sides of the highest point 8, of course, the third embodiment is only one of zigzag, and may be other shapes as well. As shown in fig. 5, the first projection formed by the outer edge of the blade tip 4 in the fourth embodiment is feather-tip-shaped along the first direction, and in the fourth embodiment, the first projection has seven repeating units 10 distributed along the first direction, each repeating unit 10 is composed of a curve facing the incoming flow and a line segment parallel to the leading edge 2 of the helicopter blade 1, the intersection point of the curve and the line segment forms a highest point 8, and the other end of the curve and the other end of the line segment form two lowest points 9, respectively. The second embodiment, the third embodiment and the fourth embodiment have the same principle as the first embodiment, and the tip shape parameters are reasonably selected through optimized design, so that the vorticity of the tip vortex can be reduced to different degrees on the premise of not adding a mechanical structure and injecting additional energy.

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 blade capable of suppressing tip vortex, said helicopter blade rotating about a first axis with a tip portion forming a tip, characterized in that a first projection of an outer edge of said tip formed on a plane perpendicular to said first axis is in the shape of a wave, undulation, sawtooth or plume in a first direction from a leading edge of said helicopter blade to a trailing edge of said helicopter blade.

2. A helicopter blade according to claim 1 wherein said tip vortex is constrained by any plane containing the outer edge of said tip and said first axis which intersects said first axis, said intersection being a line segment or smooth curve.

3. A helicopter blade according to claim 1 or claim 2 wherein said first projection when undulating in said first direction comprises four peaks and three troughs arranged alternately and in smooth transition, said peaks being further from said first axis than said troughs.