CN104494842A - Rising wingtip design method - Google Patents

Abstract

The invention belongs to the field of aircraft pneumatic layout design, and relates to a rising wingtip design method. The method comprises the steps of: building a vorticity calculating method for reducing the wingtip vortex streaming by using the wingtip reverse streaming vortex; designing a rising wingtip to partially counteract the circular reactor of the wingtip vortex to reduce the loss of wingtip three-dimensional streaming so as to achieve the purposes of reducing the whole aircraft resistance and improving the whole aircraft lift; calculating the position and the feature size of a space-inclined curved surface through the fluid mechanics to perform optimal adjustment and selection; and further performing the verification and the optimization for the design through a wind tunnel test. The rising wingtip design method creatively builds the resistance-reducing and lift-improving design principle of the wingtip reverse streaming vortex, and initiates the rising wingtip design principle and method capable of improving the lift while reducing the structural weight and simplifying the structural design.

Description

A kind of lift-rising tip design method

Technical field

The invention belongs to civil aircraft aerodynamic arrangement design field, relate to a kind of lift-rising tip design method.

Background technology

In aircraft aerodynamic arrangement designs process, engineers is continuous all the time struggles for improving lift reduction flight resistance.True aircraft is subject to the restriction of spanwise extent, produces Three dimensional Flow, make the lift of true wing be significantly less than dimensional airfoil in wing wing ending position.To increase and lift reduction to reduce the resistance that wingtip vortex causes, the various winglet of pneumatic design engineers design, and achieve positive effect.

In modern aircraft design, all to stretch out obliquely upward in host wing outer end, a little fin is feature to winglet major part, major technique hand principle is all the generation stopping and reduce wingtip vortex, plays and increases the identical effect of wing length.This type of winglet effectiveness comparison is obvious, but also gains in weight simultaneously, increases manufacturing process complexity.

Summary of the invention

Technical matters to be solved by this invention is: by setting up a kind of brand-new lift-rising principle, provide a kind of lift-rising tip design method, to increase airplane ascensional force, to reduce resistance, and simplified manufacturing technique, expendable weight simultaneously.

Technical scheme of the present invention is: a kind of lift-rising tip design method, is characterized by described method and comprise following steps:

Step one, set up the vorticity method of calculating utilizing wing tip oppositely to stream whirlpool to stream to reduce wingtip vortex, its formula is:

Γ _always=Γ _{wing tip}-Γ _lift-rising

In formula, Γ _alwaysfor wing tip total after lift-rising tip design streams vorticity, Γ _{wing tip}for the wing tip under common smooth transition wing tip state streams vorticity, Γ _lift-risingoppositely vorticity is streamed for what obtain through this lift-rising tip design method;

Step 2, design lift-rising wing tip, makes the circular rector of wingtip vortex be able to partial offset, thus reduces the loss of wing tip Three dimensional Flow, reaches and reduces the object that full machine resistance increases full machine lift, comprising:

2.1) stream vorticity according to airplane design flying speed and lift-rising wing tip, choose the average sweepback angle of wing tip, the size of sweepback angle is between 5 ° ~ 30 °;

2.2) according to the concrete aerofoil profile feature of aircraft wing, relative thickness and camber and the average sweepback angle of wing tip, the tilting curved surface of usage space clips one section of wing tip, becomes the lift-rising wing tip that can produce and oppositely stream whirlpool;

Step 3, by hydrodynamics method to step 2.2) in the position of the tilting curved surface in space and characteristic dimension be optimized adjustment and select;

Step 4, carries out checking with preferred to design further by wind tunnel test.

Beneficial effect of the present invention is: by the present invention, and initiative establishes wing tip and oppositely streams whirlpool drag reduction lift-rising principle of design, has initiated lift-rising tip design principle and the method that can also increase lift while alleviating structural weight, simplified structure design; There is provided one to improve wing tip and stream state, thus increase lift and reduce resistance, but do not increase and even alleviate wing weight, do not increase the method for designing of airfoil member manufacturing process complexity; The winglet designed by the present invention can ensure that wing area is constant, obviously plays the effect of drag reduction lift-rising when reducing wing tip weight.

Accompanying drawing explanation

Fig. 1 is that three-dimension curved surface is cut sth. askew lift-rising wingtip vortex inventive principle figure.

Fig. 2 is that three-dimension curved surface is cut sth. askew lift-rising wing tip geometric configuration schematic diagram.

Fig. 3 is that three-dimension curved surface is cut sth. askew lift-rising wing tip geometric configuration schematic diagram.

Fig. 4 is that the common wing tip of smooth transition and three-dimension curved surface lift-rising wing tip lift coefficient of cutting sth. askew contrasts figure line (results of wind tunnel).

Fig. 5 is that the common wing tip of smooth transition and three-dimension curved surface lift-rising wing tip drag coefficient of cutting sth. askew contrasts figure line (results of wind tunnel).

Detailed description of the invention

Below by specific embodiment, also the present invention is described in further detail by reference to the accompanying drawings.

Step of the present invention comprises:

With winglet, step one, mainly stopped that wingtip vortex streamed difference with former lift-rising tip design, first set up a kind of theory utilizing wing tip oppositely to stream whirlpool to stream to reduce wingtip vortex completely newly.New vorticity computing formula is:

Γ _always=Γ _{wing tip}-Γ _lift-rising

After special formed lift-rising tip design, the circular rector of wingtip vortex is able to partial offset, thus reduces the loss of wing tip Three dimensional Flow, reaches and reduces the object that full machine resistance increases full machine lift;

Step 2, choose the average sweepback angle of suitable wing tip according to airplane design flight M number, the size of sweepback angle is between 5 ° ~ 30 °;

Step 3. according to the concrete aerofoil profile feature of aircraft wing, relative thickness and camber and the average sweepback angle of wing tip are designed corresponding wing tip and are intercepted scheme, the round platform curved surface that such as space is tilting, waist drum curved surface etc.

Step 4, is optimized adjustment and selection by CFD calculating to the position of curved surface of cutting sth. askew and characteristic dimension, several preferred version can be provided alternative;

Step 5, carries out checking with preferred to design further by wind tunnel test.

Here applies the embodiment of lift-rising tip design method of the present invention.

In the design of RX1P two-seater ultra light aircraft, have employed three-dimension curved surface and to cut sth. askew lift-rising tip design.

RX1P two-seater ultra light aircraft is high mounted wing normal arrangement, employing straight wing of Denging designs, and wing area 11.42m2, wing span 9263mm, Average aerodynamic power chord length is 1250mm.With certain stagger angle and the dihedral angle.Wing tip is with certain sweepback.Wing tip place transverse cross-sectional shape adopts half-round curve smooth transition under normal circumstances.

Utilizing principle and the technology of this invention, when not changing wing planform and every basic specification size, drag reduction lift-rising optimal design being carried out to wing tip.Utilize three-dimensional optimized curved surface to cut sth. askew to the outer bottom of former wing tip, make to stream the reverse vorticity of generation, thus reach drag reduction lift-rising, alleviate the effect of structural weight simultaneously.Specific design step is as follows:

Step one, RX1P two-seater ultra light aircraft design cruising speed is 216 kilometers/hour, and adopt straight wing, aerofoil profile is NASA3010, and confirmation can adopt this method design lift-rising wing tip to carry out drag reduction lift-rising to full machine;

Step 2, choose the average sweepback angle of suitable wing tip according to RX1P two-seater ultra light aircraft design flight M number, the size of sweepback angle is between 5 ° ~ 30 °, and this example design wing tip average sweepback angle expected value is 20 °;

Step 3. according to the concrete aerofoil profile feature of RX1P two-seater ultra light aircraft wing, relative thickness and camber and the average sweepback angle of wing tip are designed corresponding wing tip and are intercepted scheme, adopt the round platform curved surface that space is tilting, wing tip is intercepted, the axis of small circle 400mm of round platform, axis of great circle 480mm, round platform height 2089mm, wing tip is intercepted with certain space angle (direction vector for 0.98,0.028,0.196).

Step 4, by carrying out CFD calculating to RX1P two-seater ultra light aircraft, the wing tip scheme of cutting sth. askew obtained in step 3 has significant drag reduction lift-rising effect, and is that main scheme is optimized adjustment and selection to the position of curved surface of cutting sth. askew and characteristic dimension with it, provides 2 alternativess;

Step 5, is verified design further by wind tunnel test, confirms that this method of designing is effective, obviously improves the aeroperformance of RX1P two-seater ultra light aircraft.

Provide below in conjunction with accompanying drawing and further illustrate.Fig. 1 and Fig. 2,3 sets forth cut sth. askew lift-rising wingtip vortex schematic diagram and three-dimension curved surface of three-dimension curved surface and to cut sth. askew lift-rising wing tip geometric configuration schematic diagram.

Fig. 4 and Fig. 5 sets forth cut sth. askew lift-rising wing tip lift coefficient and drag coefficient of the common wing tip of smooth transition and three-dimension curved surface and contrasts figure line (results of wind tunnel).

As can be seen from contrast figure line, maximum lift coefficient improves 5%.When the angle of attack is 0 °, the drag coefficient of common sweepback wing tip is 0.03375, and the drag coefficient of sharp sweepback wing tip is 0.02906, and drag coefficient reduces by 0.005, and reduce by 1/6th, drag-reduction effect is fine.Amount to into the lift increment under identical resistance, lift increase about 17% under cruising speed.The angle of attack is very little close to resistance increase during 13 ° of maximum lift states, and the angle of attack increases resistance again and is significantly increased, but now resistance has not been subject matter.

Three-dimension curved surface lift-rising wing tip of cutting sth. askew has obvious drag reduction lift-rising effect, obviously can reduce cruise drag and improve maximum lift.

Claims (1)

1. a lift-rising tip design method, is characterized by described method and comprises following steps:

Step one, set up the vorticity method of calculating utilizing wing tip oppositely to stream whirlpool to stream to reduce wingtip vortex, its formula is:

Г _always=Г _{wing tip}-Г _lift-rising

In formula, Г _alwaysfor wing tip total after lift-rising tip design streams vorticity, Г _{wing tip}for the wing tip under common smooth transition wing tip state streams vorticity, Г _lift-risingoppositely vorticity is streamed for what obtain through this lift-rising tip design method;

Step 2, design lift-rising wing tip, makes the circular rector of wingtip vortex be able to partial offset, thus reduces the loss of wing tip Three dimensional Flow, reaches and reduces the object that full machine resistance increases full machine lift, comprising:

2.1) stream vorticity according to airplane design flying speed and lift-rising wing tip, choose the average sweepback angle of wing tip, the size of sweepback angle is between 5 ° ~ 30 °;

2.2) according to the concrete aerofoil profile feature of aircraft wing, relative thickness and camber and the average sweepback angle of wing tip, the tilting curved surface of usage space clips one section of wing tip, becomes the lift-rising wing tip that can produce and oppositely stream whirlpool;

Step 3, by hydrodynamics method to step 2.2) in the position of the tilting curved surface in space and characteristic dimension be optimized adjustment and select;

Step 4, carries out checking with preferred to design further by wind tunnel test.