阅读说明：本技术 一种具有低阻高发散马赫数的共轴双旋翼高速直升机桨尖翼型 (Coaxial dual-rotor high-speed helicopter tip airfoil with low resistance and high divergence Mach number ) 是由 高正红 赵欢 夏露 于 2020-12-14 设计创作，主要内容包括：本发明设计了一种具有低阻高发散马赫数的共轴双旋翼高速直升机桨尖翼型,翼型前缘半径为0.00679,翼型最大厚度为0.0700,位于翼型43.3％弦长处,最大弯度为0.003260,位于翼型17.7％弦长处,后缘夹角为2.20度。本发明翼型在设计的高、中、低马赫数范围内,低速特性损失不大的情况下,高速特性提升显著且更加稳健。其中在高速零升状态下及其附近范围内,相对于对比法国经典OA系列翼型OA407发明翼型具有非常低的阻力系数显著降低,且更加稳健,同时发明翼型阻力发散马赫数显著提高,在宽马赫数范围内保持了更低的阻力系数和低阻范围,并在整个包线范围内保持了相对于经典OA407翼型更好的力矩特性,为共轴双旋翼高速直升机桨尖翼型的设计奠定了基础。(The invention designs a tip airfoil of a coaxial dual-rotor high-speed helicopter with low resistance and high divergence Mach number, the radius of the front edge of the airfoil is 0.00679, the maximum thickness of the airfoil is 0.0700 and is positioned at the chord length of 43.3 percent of the airfoil, the maximum camber is 0.003260 and is positioned at the chord length of 17.7 percent of the airfoil, and the included angle of the rear edge is 2.20 degrees. The high-speed characteristic of the airfoil is improved remarkably and more stably under the condition that the loss of the low-speed characteristic is not large in the designed high, medium and low Mach number ranges. Compared with the French classical OA series airfoil OA407, the airfoil of the invention has the advantages that the drag coefficient is remarkably reduced and is more stable in a high-speed zero-lift state and in a near range, meanwhile, the drag divergence Mach number of the airfoil is remarkably improved, the lower drag coefficient and the low-drag range are kept in a wide Mach number range, the better moment characteristic compared with the classical OA407 airfoil is kept in the whole envelope range, and a foundation is laid for the design of the tip airfoil of the coaxial dual-rotor high-speed helicopter.)

1. A coaxial dual rotor high speed helicopter tip airfoil with low resistance and high divergence Mach number, characterized by: the radius of the front edge of the airfoil is 0.00679, the maximum thickness of the airfoil is 0.0700, the maximum camber is 0.003260 and is located at the chord length of the airfoil of 43.3%, and the included angle of the rear edge is 2.20 degrees.

2. A coaxial twin rotor high speed helicopter tip airfoil with low drag and high divergence mach number according to claim 1 further comprising: the geometrical coordinate expressions of the upper surface and the lower surface of the airfoil are respectively

Wherein z is_u(x) And z_l(x) Respectively is the vertical coordinate position of the upper surface and the lower surface of the unit airfoil profile, x is the horizontal coordinate position of the profile point of the unit airfoil profile, A_u，iAnd A_l，i(i is 0,1,2 …,7) is the wing profile upper and lower surface fitting coefficient in the wing profile expression, z is_te0.00100; the coefficient of fit of the upper and lower surfaces of the airfoil profile is

3. A coaxial twin rotor high speed helicopter tip airfoil with low drag and high divergence mach number according to claim 2 further comprising: the fitting coefficients of the upper surface and the lower surface of the airfoil profile are as follows:

4. a coaxial twin rotor high speed helicopter tip airfoil with low drag and high divergence mach number according to claim 1 further comprising: the upper and lower surface data of the airfoil profile are:

airfoil upper surface data

Airfoil lower surface data

Technical Field

The invention relates to the technical field of blade airfoil design of coaxial dual-rotor high-speed helicopters, in particular to a tip airfoil of a coaxial dual-rotor high-speed helicopter, which has low resistance and high divergence Mach number.

Background

The conventional configuration helicopter is limited by the fact that the rotor backward blades have a large separation flow phenomenon under the condition of high-speed forward flight at about 300km/h, and even reach 85% of the radial region of the blades when the separation is serious, so that the backward blades have poor aerodynamic characteristics and cannot generate lift force and forward thrust, the forward blades and the backward blades meet the matching of the aerodynamic characteristics of the rotors, and the blade profiles of the forward blades cannot work in the range of attack angles corresponding to high lift-drag ratios, so that the aerodynamic efficiency of the helicopter during high-speed large forward ratio flight is seriously influenced.

In order to break through the speed limit of helicopters, new configurations and new concepts of helicopters are explored and researched in all countries in the world. Existing high-speed helicopter configurations mainly include compound, tilt, and stall modes. The combined type comprises a coaxial dual-rotor helicopter and a helicopter with an auxiliary propulsion or lift device configured by an conventional rotor/Advancing Blade Concept (ABC) rotor. The ABC rotor system proposed in 1964 by western corss corporation of america, which included a pair of counter-rotating, coaxial, completely rigid, hingeless rotors with the forward blades of the upper and lower rotors providing the main lift during forward flight at high speed, and the aft blades unloading, producing little lift, thereby slowing or even eliminating the separation of the air flow in the reverse flow region of the aft blades, and ensuring forward flight at high speed. This configuration has been continuously developed and validated by western skiy corporation for the last 50 years as proposed by ABC rotor. In 1970, a 40-foot ABC test rotor was manufactured by Western Corkski and tested in a NASA-AMES wind tunnel. In 1972, the united states army signed a contract with western costas corporation, asking him to design, manufacture and test for an ABC rotorcraft XH-59A. In 1973, the first flight was achieved, and during the subsequent trial flight for a total of 170 hours, the maximum flat flight speed reached 238kt (about 441 km/h). In 2008, the western costky company introduced an X2 validation machine that employed a coaxial rigid rotor with a propeller added to the tail. The maximum flat flight speed of the X2 in the test flight of 2010 reaches 250kt (about 460km/h), which is twice that of the active eagle helicopter and 1.5 times that of the 'Apache' helicopter. In 2015, an S-97 composite high-speed helicopter developed by western science foundation and based on an ABC rotor wing smoothly flies for the first time, and the designed hourly speed of the helicopter reaches 260kt (480 km/h). A large number of wind tunnel tests and demonstration machine argumentations show that the high-speed helicopter adopting the ABC rotor wing has hovering and high-speed flight capabilities, has the characteristics of compact structure, good aerodynamic performance, maneuverability and the like, and represents the development trend of the high-speed helicopter.

The rotor is a key component for generating lift and thrust of a helicopter, and the performance of the rotor is mainly determined by the performance of an airfoil, which significantly influences the forward flight speed, the quick maneuvering performance, the take-off and landing performance, the control quality and the flight efficiency of all flight phases of the helicopter. The working mechanism of the coaxial rigid rotor wing is quite different from that of the traditional single rotor wing, and the requirement on the aerodynamic performance of the wing profile is greatly different. Helicopter rotors need to provide sufficient drag to perform hover, maneuver, and forward flight operations. For a single-rotor helicopter, in order to maintain the balance of the helicopter body, the resultant force of the pulling forces generated by the forward side and the backward side of the blades needs to act on the rotating shaft. The incoming flow speeds of the forward side and the backward side are greatly different, so that the conventional rotor wing profile needs to have low-speed high-lift characteristics, high-speed low-resistance characteristics and the like. For the coaxial rigid rotor wing, the upper rotor wing and the lower rotor wing perform contra-rotating movement, so that forward blades are arranged on two sides of a paddle disc, sufficient pulling force can be provided by fully utilizing high dynamic pressure of the forward blades, and the backward blades do not need to provide the pulling force; the retreating blades can be unloaded during high-speed forward flight to avoid the resistance and noise surge caused by a large-range reverse flow area, so that the coaxial rigid rotor helicopter can generally obtain higher forward flight speed. And the increase of the forward flight speed leads to the harsher flow field environment of the backward blades, and the X2TD of the Western scientific base verifies that the backward blades are even more than 80 percent in a reverse flow zone when the aircraft flies forward at a high speed. Therefore, the coaxial rigid rotor wing profile needs to have good high-speed low-resistance characteristics, the blade tip profile needs to have high resistance divergence Mach number, and the root profile needs to have flow separation resistance and low-resistance characteristics in a reverse flow region. The whole performance and working state of the rotor wing require that the rotor wing profile has a high maximum lift coefficient in a low Mach number to medium subsonic speed state, and has a small zero lift resistance coefficient and a high resistance divergence characteristic in a transonic speed state. At the same time, the rotor wing profile also needs to have a small pitching moment in order to reduce the torque and handling loads. In addition, in order to ensure the hovering characteristic of the helicopter, the lift-drag ratio in the hovering state should be high. Therefore, the design of the rotor wing profile is a comprehensive optimization design problem with multiple design points, multiple targets and multiple constraints.

Disclosure of Invention

In order to solve the problems in the prior art, the invention designs the coaxial dual-rotor high-speed helicopter tip airfoil with low resistance and high divergence Mach number, the radius of the front edge of the airfoil is smaller, and the proper accelerated flow and the lower suction peak value of the front edge are ensured; the curvature of the upper surface of the airfoil changes slowly from the front edge, the camber of the front edge is reduced remarkably, the change is gentle after the flow is accelerated to a suction peak, the shock wave resistance is reduced remarkably by a lower pressure recovery point and a designed double weak shock wave pressure distribution form, the robustness of the airfoil resistance characteristic to the change of states such as Mach number is enhanced, the resistance divergence Mach number reaches 0.875, and the resistance coefficient of a divergence point is 0.00710.

Compared with the classical OA407 wing profile of the high-speed rotor wing profile with the same thickness, the wing profile has the advantages that the radius of the front edge is smaller, the maximum camber is smaller, the maximum thickness is moved backwards, so that the suction peak value generated by the upper surface and the lower surface of the wing profile is not high, the typical weak shock wave pressure distribution form is developed, and the development of shock waves is controlled. Meanwhile, the camber is reduced from the front edge of the airfoil to the position of 90 percent of chord length, the camber of the rear edge is increased (recurved), and the maximum thickness position moves backwards, so that the moment coefficient (absolute value) of the airfoil is remarkably small, and the good moment characteristic in the whole high-speed and low-speed range is maintained.

Specifically, the technical scheme of the invention is as follows:

the tip airfoil of the coaxial dual-rotor high-speed helicopter with low resistance and high divergence number has a leading edge radius of 0.00679, a maximum thickness of 0.0700, a maximum camber of 0.003260 and a trailing edge included angle of 2.20 degrees, and is positioned at the chord length of 43.3% of the airfoil.

Further, the geometrical coordinate expressions of the upper surface and the lower surface of the airfoil are respectively

Wherein z is_u(x) And z_l(x) Respectively is the vertical coordinate position of the upper surface and the lower surface of the unit airfoil profile, x is the horizontal coordinate position of the profile point of the unit airfoil profile, A_u,iAnd A_l,i(i is 0,1,2 …,7) is the wing profile upper and lower surface fitting coefficient in the wing profile expression, z is_te0.00100; the coefficient of fit of the upper and lower surfaces of the airfoil profile is

Further, the fitting coefficients of the upper surface and the lower surface of the airfoil are preferably as follows:

further, the data of the upper and lower surfaces of the tip airfoil of the coaxial dual-rotor high-speed helicopter with low resistance and high divergence mach number are given in the following table:

airfoil upper surface data

Coordinates of the lower surface

Advantageous effects

The invention provides a tip airfoil profile of a coaxial dual-rotor high-speed helicopter with low resistance and high divergence Mach number. The high-speed characteristic of the airfoil is improved remarkably and more stably under the condition that the loss of the low-speed characteristic is not large in the designed high, medium and low Mach number ranges. Compared with the French classical OA series airfoil OA407, the airfoil of the invention has the advantages that the drag coefficient is remarkably reduced and is more stable in a high-speed zero-lift state and in a near range, meanwhile, the drag divergence Mach number of the airfoil is remarkably improved, the lower drag coefficient and the low-drag range are kept in a wide Mach number range, the better moment characteristic compared with the classical OA407 airfoil is kept in the whole envelope range, and a foundation is laid for the design of the tip airfoil of the coaxial dual-rotor high-speed helicopter.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a view of the airfoil geometry of the present invention.

FIG. 2 is a pressure profile plot at design points for an airfoil of the present invention.

FIG. 3 is a comparison of the airfoil geometry of the present invention with an OA407 airfoil geometry.

FIG. 4 is a comparison of the airfoil geometry camber of the present invention with an OA407 airfoil geometry camber.

FIG. 5 is a comparison of airfoil geometry of the present invention and OA407 airfoil geometry thickness.

FIG. 6 is a comparison graph of the pressure profile distribution at a survey point for the airfoil of the present invention and OA407 airfoil.

FIG. 7 is a comparison of the resistance-divergence curves of the airfoil of the present invention and OA407 airfoil (CL 0.00, Re/Ma 7.20e 6).

FIG. 8 is a comparison of the moment characteristics of the airfoil of the present invention and OA407 airfoil (CL 0.00, Re/Ma 7.20e 6).

Fig. 9 is a comparison of the low speed lift characteristics of the airfoil of the present invention and the OA407 airfoil (Ma 0.30 and Re 2.16e 6).

FIG. 10 is a comparison of the low speed lift characteristics of the airfoil of the present invention and the OA407 airfoil (Ma 0.40, Re 2.88e 6).

FIG. 11 is a comparison of the low speed lift characteristics of the airfoil of the present invention and the OA407 airfoil (Ma 0.50 and Re 3.60e 6).

Detailed Description

The conventional configuration helicopter is limited by the fact that a phenomenon of large separation flow exists in the backward-moving blades of the rotor under the condition of high-speed forward flight at about 300km/h (large forward ratio), when the separation is serious, even the separation reaches 85% of the radial region of the blades, so that the aerodynamic characteristics of the backward-moving blades are poor, the lift force and the forward thrust cannot be generated, the forward-moving blades and the backward-moving blades are matched for meeting the aerodynamic characteristics of the rotor, the blade profiles (wing profiles) of the forward-moving blades cannot work in the range of attack angles corresponding to the high lift-drag ratio, and the aerodynamic efficiency of the helicopter during high-speed large forward ratio flight is seriously influenced.

Therefore, according to the special task requirements of different helicopters in different periods, the high-performance rotor wing profiles meeting different performance requirements are designed according to the characteristics of the unsteady flow field of the helicopter rotor and the motion rule of the blades. The coaxial rigid rotor high-speed helicopter based on the forward-moving blade concept is a high-speed helicopter layout which is innovated and systematically researched by western costas company in the United states. Compared with the conventional helicopter, the flight speed of the coaxial dual-rotor helicopter is remarkably improved, for example, the flight speed of an S-97 helicopter can reach 482km/h, and the coaxial dual-rotor helicopter has potential application value. Rotor wing profile design research is slow relative to fixed wing aircraft wing profiles, primarily due to the complex design requirements and constraints of rotor wing profiles. The airfoil profile as a main element of the rotor blade largely determines the performance of the helicopter, so that the design of the high-performance rotor airfoil profile is particularly important for further improving the overall performance of the helicopter.

The coaxial dual-rotor high-speed helicopter tip airfoil with the low resistance and the high divergence Mach number, which is proposed in the embodiment, has the high-speed investigation state that the Mach number is 0.87, the lift coefficient is 0.00, the Reynolds number is 6.264e6, the turbulence degree is 0.5%, and the turbulence viscosity ratio is 10. The radius of the front edge of the airfoil is 0.00679, the maximum thickness of the airfoil is 0.0700, the maximum camber is 0.003260 and is located at the chord length of the airfoil of 43.3%, and the included angle of the rear edge is 2.20 degrees. It should be noted that, in the field of airfoil design, parameter descriptions are described by using dimensionless quantities, so that the leading edge radius, the maximum thickness, the maximum camber and subsequent airfoil coordinate descriptions are described by using dimensionless quantities, and the dimensionless process is based on the airfoil chord length c.

The geometrical coordinate expressions of the upper surface and the lower surface of the specific airfoil profile are respectively

Wherein z is_u(x) And z_l(x) The vertical coordinate positions of the upper surface and the lower surface of the unit wing profile are respectively, x is the horizontal coordinate position of the outline point of the unit wing profile, and certainly, in the field of wing profile design, the range of the horizontal coordinate of the outline point of the unit wing profile is 0-1 according to dimensionless quantity expression; a. the_u,iAnd A_l,i(i is 0,1,2 …,7) is the fitting coefficient of the upper and lower surfaces of the airfoil expression, z is_te0.00100; the above expression of the airfoil profile has fitting coefficients of

And through numerical calculation, the airfoil profile obtained by the coefficient within the range of the upper and lower fluctuation not more than 0.5 percent has better performance.

The data for the upper and lower surfaces of the tip airfoils of the coaxial dual rotor high speed helicopter of this embodiment having a low resistance and high divergence mach number are given in tables 1 and 2 below

TABLE 1 airfoil top surface data

TABLE 2 lower surface coordinates

Comparing the aerodynamic performance calculation of the airfoil with that of a classical OA407 airfoil, it can be seen that the high-speed resistance divergence characteristic of the airfoil is improved remarkably, the basic resistance is reduced remarkably, and the moment characteristic is better in all states under the condition that the loss of the low-speed characteristic is not large at the design point and near the design point.

TABLE 3 aerodynamic characteristics of the airfoil of the invention

Ma	Cl	Cd	Cm
				0.800	0.0000	0.00655	-0.00159
0.820	0.0000	0.00701	-0.00141
				0.840	0.0000	0.00720	-0.00060
0.850	0.0000	0.00722	-0.00079
				0.855	0.0000	0.00717	-0.00093
0.860	0.0000	0.00702	-0.00079
				0.865	0.0000	0.00669	-0.00065
0.870	0.0000	0.00674	-0.00346
				0.875	0.0000	0.00710	-0.00668
0.880	0.0000	0.00927	-0.00747
				0.885	0.0000	0.01262	-0.00795
0.890	0.0000	0.01675	-0.00916

TABLE 4 aerodynamic characteristics Table for comparative airfoils (classic OA407 airfoils)

Ma	Cl	Cd	Cm
				0.800	0.0000	0.00775	-0.00584
0.820	0.0000	0.00794	-0.00600
				0.840	0.0000	0.00787	-0.00758
0.850	0.0000	0.00782	-0.01098
				0.855	0.0000	0.00800	-0.01419
0.860	0.0000	0.00853	-0.01870
				0.865	0.0000	0.00944	-0.02400
0.870	0.0000	0.01084	-0.02948
				0.875	0.0000	0.01289	-0.03468
0.880	0.0000	0.01559	-0.03879
				0.885	0.0000	0.01913	-0.04364
0.890	0.0000	0.02318	-0.04685

As shown, the airfoil of the embodiment has a smaller leading edge radius (A) relative to a comparison OA series airfoil 407 of a French classical same-thickness high-speed rotor airfoil, so that the suction peak value is kept lower after the airflow around the leading edge of the airfoil is accelerated, and the suction peak point (A') is kept appropriate to help reduce the pressure recovery point of the trailing edge of the airfoil. Then starting from the front edge (A) of the airfoil, the curve section B where the upper surface of the airfoil is located keeps small and slow camber change and proper and low curvature increase, the camber of the upper surface of the front edge of the airfoil is remarkably reduced until reaching the maximum thickness position, so that the pressure distribution of the upper surface of the airfoil is gently changed from the position A ', a classical' double weak shock wave 'pressure distribution form appears when reaching the position B', the shock wave intensity is remarkably reduced, and the corresponding shock wave on the lower surface of the flow field of the airfoil is also weak. The pressure distribution form of the design not only obviously reduces the resistance of the airfoil flow field, but also greatly enhances the robustness of the airfoil flow field after changing along with the Mach number and the attack angle, thereby maintaining the low resistance characteristic of the airfoil in a certain Mach number range and obviously improving the resistance divergence Mach number.

The airfoil of the invention is designed from the position C to the trailing edge of the airfoil and the thickness is not changed any more, the integral area generated by the pressure distribution at the position C' controls the increase of the low head moment of the airfoil (the moment reference point is 1/4 chord line position), so that the airfoil moment coefficient is better than that of an OA407 airfoil under the same state, the absolute value is far less than 0.02, namely the moment characteristic of the airfoil of the high-speed rotor is effectively improved, and the trim resistance is reduced. Natural transition state calculations show that in the high speed zero rise state (Ma 0.87, CL 0.00, Re 6.264e6) and its vicinity, the airfoil of the present invention has a very low drag coefficient, which is 0.00673 at the point of investigation, which is a 41.1counts reduction over the drag coefficient 0.01084 of the comparative OA407 airfoil. Meanwhile, the resistance divergence Mach number of the airfoil profile is 0.875, which is 0.021 higher than that of the OA407 airfoil profile which is 0.854, and a lower resistance coefficient and a lower low resistance range are kept in a wide Mach number range. And maintains better torque characteristics over the classic OA407 airfoils throughout the high, medium and low mach number (Ma 0.2 to Ma 0.87).

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.