Double-layer horizontal tail structure supported by truss and design method

Abstract

The invention belongs to the technical field of aerodynamic design of helicopters, and particularly relates to a design method of a truss-supported double-layer horizontal tail. The lower-layer horizontal tail is obliquely installed, the root of the lower-layer horizontal tail is connected with the fuselage, the tip of the lower-layer horizontal tail is connected with the upper-layer horizontal tail to form a truss supporting structure, and the upper-layer horizontal tail, the lower-layer horizontal tail and the fuselage form a closed force bearing frame.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of helicopter aerodynamic design, and particularly relates to a design method of a double-layer horizontal tail supported by a truss. BACKGROUND

[0002] The horizontal tail is one of the important aerodynamic components of a helicopter, and provides the longitudinal stability of the helicopter in the forward flight state. When the helicopter flies in the transition speed segment, the downwash of the rotor acting on the horizontal tail will increase sharply, causing sudden changes in the aerodynamic load of the horizontal tail, sudden changes in the pitch attitude of the helicopter, and an increase in the rotor load, which adversely affects the flight quality and flight load of the helicopter. Due to the reduction of the rotor radius of modern helicopters, the rotor induction increases, and the interference problem between the rotor and the horizontal tail in the transition speed segment is more prominent, so the rotor / horizontal tail aerodynamic interference problem is becoming more and more serious in the design of helicopters.

[0003] To alleviate the problem of aerodynamic interference between the rotor and the horizontal tail in the transition speed segment, the S-70 helicopter of Sikorsky Company adopts a full-motion horizontal tail technology, which changes the installation angle of the horizontal tail to reduce the change in the aerodynamic angle of attack of the horizontal tail caused by the downwash of the rotor, and controls the change in the aerodynamic load of the horizontal tail, but this method is complex in structure, heavy in weight, and high in cost. The Chinese Helicopter Design Institute proposed a double-layer horizontal tail configuration for reducing the influence of aerodynamic interference in a design method for a helicopter horizontal tail (Patent Publication No. CN115758575A), which is two horizontal tails arranged independently and in parallel, greatly reducing the chord length of the single-layer horizontal tail, and greatly increasing the aspect ratio of the horizontal tail. The slender horizontal tail brings adverse effects to the structural design. SUMMARY

[0004] The present application provides a horizontal tail design configuration and method that reduces the downwash effect of the rotor on the horizontal tail in the transition speed segment while meeting the longitudinal stability requirements of the helicopter.

[0005] In a first aspect, the present application provides a double-layer horizontal tail configuration supported by a truss, the lower horizontal tail is installed obliquely, the root of the lower horizontal tail is connected to the fuselage, the tip of the lower horizontal tail is connected to the upper horizontal tail, forming a truss support structure, and the upper horizontal tail, the lower horizontal tail and the fuselage form a closed load-bearing frame.

[0006] Further, the upper horizontal tail is arranged on the load-bearing frame at the upper and rear parts of the tail section to determine the longitudinal and vertical installation positions of the root of the upper horizontal tail; and the lower horizontal tail is arranged at the lower part of the tail section to reduce the aerodynamic interference between the upper and lower horizontal tails and determine the vertical installation position of the root of the lower horizontal tail.

[0007] Further, in the heading direction, the lower horizontal tail is located below and rearward of the upper horizontal tail.

[0008] In a second aspect, the present application also provides a design method of a truss-supported double-layer tail, comprising: S1, establishing a flight dynamics model of the helicopter, preliminarily determining the areas of the upper and lower horizontal tails to ensure that the longitudinal forward flight stability requirements of the helicopter are met, preliminarily determining the installation angles of the upper and lower horizontal tails to ensure that the attitude angle of forward flight and the load are within a reasonable range, and preliminarily determining the connection points of the upper and lower horizontal tails to ensure that the aerodynamic force distribution of the horizontal tail is reasonable and the force on the joint of the horizontal tail and the tail section is reasonable. S2, establishing an interference calculation model including the rotor, the fuselage, the upper horizontal tail and the lower horizontal tail of the helicopter, calculating and analyzing the interference flow field of the rotor on the upper and lower horizontal tails at each forward flight speed, and determining the strong interference state of the rotor on the upper and lower horizontal tails. S3, obtaining the rotor wake inclination angle χ at the position of the upper and lower horizontal tails in the strong interference state. S4, adjusting and determining the longitudinal installation position of the root of the lower horizontal tail, so that the angle between the line connecting the 1 / 4 chord line points of the upper and lower horizontal tails at the same spanwise position and the horizontal plane is equal to the rotor wake inclination angle χ. S5, adjusting the chord length of the upper and lower horizontal tails while keeping the total area of the upper and lower horizontal tails unchanged, so that the aerodynamic interference of the rotor on the upper and lower horizontal tails in the strong interference state is minimized.

[0009] Further, the method further comprises: S6, carrying out a scaled fuselage wind tunnel test: obtaining the fuselage aerodynamic characteristic data including the double-layer tail and the blade root through the scaled fuselage wind tunnel test, and calculating and evaluating the flight load and flight quality of the helicopter according to the above data; by adjusting the area and installation angle of the double-layer tail, changing the fuselage aerodynamic characteristics, so that the flight load and flight quality of the helicopter meet the design requirements, and further determining the area and installation angle of the truss-supported double-layer tail.

[0010] Further, the method further comprises: S7, carrying out a rotor-to-fuselage interference test: capturing the strong interference state of the rotor on the double-layer tail in the transition speed range through the rotor-to-fuselage interference test, adjusting the chord length of the double-layer tail, the longitudinal installation position of the root of the lower horizontal tail, and the connection points of the upper and lower horizontal tails, so that the aerodynamic interference of the rotor on the double-layer tail is minimized, and further determining the chord length of the truss-supported double-layer tail, the longitudinal installation position of the root of the lower horizontal tail, and the connection points of the upper and lower horizontal tails.

[0011] Further, the method further comprises: S8, flight test: through flight test, the effect of the double flat tail of the truss support in strong interference state on reducing the interference of the rotor on the double flat tail is verified, and the parameters of the double flat tail configuration are optimized according to the flight test in the whole flight envelope, and finally the design parameters of the double flat tail of the truss support are determined.

[0012] In summary, the beneficial effects of the present application are as follows: The new flat tail configuration provided by the present application can generate sufficient aerodynamic force to ensure the longitudinal stability of the helicopter when flying at medium and high speeds, can weaken the rotor / flat tail aerodynamic interference when flying at the transition speed, can reduce the attitude change amount of the fuselage and the increase of the flight load caused by the rotor downwash on the flat tail, and has simple structure, reasonable force transmission path and good economy. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is the truss-supported double flat tail structure involved in the present application; 1 is a part of the tail structure of the helicopter, 2 is the upper flat tail, 3 is the lower flat tail, 4 is the connecting joint of the upper flat tail and the tail of the helicopter, 5 is the connecting joint of the lower flat tail and the tail of the helicopter, and 6 is the connecting joint of the upper flat tail and the lower flat tail; Figure 2 is the plan view of the truss-supported double flat tail involved in the present application; Figure 3 is the side view of the truss-supported double flat tail involved in the present application; Figure 4 is the rear view of the truss-supported double flat tail involved in the present application. DETAILED DESCRIPTION

[0014] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings.

[0015] The present application aims at the problem that the rotor downwash acting on the flat tail will increase sharply when the helicopter flies at the transition speed, causing sudden change of the flight attitude of the helicopter and sudden increase of the rotor load, and proposes a truss-supported double flat tail design configuration. When flying at medium and high speeds, the upper and lower flat tails generate aerodynamic lift and drag at the same time, meeting the longitudinal stability requirements of the helicopter. When flying at the transition speed, the shielding effect of the upper flat tail on the rotor downwash is utilized to reduce the interference of the rotor downwash on the lower flat tail. The lower flat tail is installed obliquely, the root of the flat tail is connected with the fuselage, and the tip is connected with the upper flat tail, forming a truss support structure. The upper flat tail, the lower flat tail and the fuselage form a closed force-bearing frame, and the force transmission path is more reasonable.

[0016] Technical solution: The double-layer flat tail supported by the truss is composed of an upper flat tail arranged horizontally or nearly horizontally, a lower flat tail arranged obliquely, a connecting piece of the upper flat tail and the lower flat tail, a connecting joint of the upper flat tail and the fuselage, and a connecting joint of the lower flat tail and the fuselage. The design method comprises the following steps: According to the configuration of the helicopter, the tail section structure and the structural force transmission path, the upper flat tail is arranged on the load-bearing frame at the upper and rear parts of the tail section as much as possible without interfering with other components, and the longitudinal and vertical installation positions of the root of the upper flat tail are determined; the lower flat tail is arranged at the lower part of the tail section as much as possible to reduce the aerodynamic interference between the flat tails, and the vertical installation position of the root of the lower flat tail is determined. Further, a flight dynamics model of the helicopter is established, the areas of the upper and lower flat tails are preliminarily determined to ensure that the longitudinal forward flight stability requirements of the helicopter are met, the installation angles of the upper and lower flat tails are preliminarily determined to ensure that the attitude angle of forward flight and the load are within a reasonable range, and the connection points of the upper and lower flat tails are preliminarily determined to ensure that the aerodynamic force distribution of the flat tails is reasonable and the stress of the flat tails and the tail section joints is reasonable. Further, an interference calculation model including the helicopter rotor, the fuselage and the flat tail is established, the rotor / flat tail interference flow field at each forward flight speed from hovering to the non-surmountable speed is calculated and analyzed, and the strong interference state of the rotor to the flat tail is determined. Further, the rotor wake inclination angle χ at the position of the flat tail under the strong interference state is obtained. Further, the longitudinal installation position of the root of the lower flat tail is adjusted and determined, so that the angle between the line connecting the 1 / 4 chord line points of the upper flat tail and the lower flat tail at the same spanwise position and the horizontal plane is equal to the rotor wake inclination angle χ, and the shielding effect of the upper flat tail on the rotor downwash is maximized, so that the rotor downwash acts as little as possible on the lower flat tail, thereby reducing the interference effect of the rotor downwash in the transition speed range. Further, under the premise of keeping the total area of the upper and lower flat tails unchanged, the chord lengths of the upper and lower flat tails are optimized and adjusted to minimize the rotor / flat tail aerodynamic interference under the strong interference state.

[0017] The above steps preliminarily determine the area, installation angle, installation position of the fuselage and connection point of the upper flat tail and the lower flat tail of the double-layer flat tail supported by the truss through theoretical calculation. Further steps are needed to finally determine the design configuration.

[0018] Further, a scale model fuselage wind tunnel test is carried out. The fuselage aerodynamic characteristic data including the flat tail and the blade root are obtained through the scale model fuselage wind tunnel test, and the flight load and flight quality of the helicopter are calculated and evaluated according to the above data. By adjusting the area and installation angle of the flat tail, the fuselage aerodynamic characteristics are changed, so that the flight load and flight quality of the helicopter meet the design requirements, and the area and installation angle of the double-layer flat tail supported by the truss are further determined.

[0019] Further, the rotor / fuselage interference test is carried out. The strong interference state of the rotor to the horizontal tail in the transition speed section is captured through the rotor / fuselage interference test, the chord length of the horizontal tail, the longitudinal installation position of the root of the lower horizontal tail and the connecting point of the upper and lower horizontal tails are adjusted, so that the aerodynamic interference of the rotor to the horizontal tail is minimized, and the chord length of the truss-supported double horizontal tail, the longitudinal installation position of the root of the lower horizontal tail and the connecting point of the upper and lower horizontal tails are further determined.

[0020] Further, the flight test is carried out. The effect of the truss-supported double horizontal tail on reducing the rotor / horizontal tail interference in the strong interference state is verified through the flight test, the horizontal tail configuration parameters are optimized according to the flight test in the whole flight envelope, and finally the design parameters of the truss-supported double horizontal tail are determined.

[0021] The truss-supported double horizontal tail configuration of the present application has the following technical effects: In the transition speed section, the change amount of the fuselage attitude and the increase amount of the flight load caused by the rotor downwash acting on the horizontal tail can be reduced; The horizontal tail can generate sufficient aerodynamic force to meet the requirements of the forward flight longitudinal stability of the helicopter at medium and high speeds; The aspect ratio of the horizontal tail is improved, and the aerodynamic efficiency of the horizontal tail is improved; The root of the lower horizontal tail is connected with the fuselage, the tip is connected with the upper horizontal tail, a truss support structure is formed, the upper horizontal tail, the lower horizontal tail and the fuselage constitute a closed force-bearing frame, and the force transmission path is reasonable.

[0022] The structure is simple, there is no any moving part, and the economy is good.

Claims

1. A twin-tail configuration of a truss-supported biplane characterized in that, The lower horizontal tail is obliquely installed, the root of the lower horizontal tail is connected with the fuselage, and the tip of the lower horizontal tail is connected with the upper horizontal tail, forming a truss support structure, and the upper horizontal tail, the lower horizontal tail and the fuselage constitute a closed force-bearing frame.

2. A twin-tail configuration of a truss-supported double-decker aircraft in accordance with claim 1, characterized by The upper horizontal tail is arranged on the force-bearing frame at the upper and rear part of the tail section to determine the longitudinal and vertical installation positions of the root of the upper horizontal tail; and the lower horizontal tail is arranged at the lower part of the tail section to reduce the aerodynamic interference between the upper and lower horizontal tails and to determine the vertical installation position of the root of the lower horizontal tail.

3. A twin-tail configuration of a truss-supported double decked tailplane as claimed in claim 1, characterized in that, In the heading direction, the lower horizontal tail is located below and rearward of the upper horizontal tail.

4. A method of designing a twin-tail design with truss support, characterized by, The method is used for designing the double-layer horizontal tail configuration as claimed in any one of claims 1-3, and the method comprises: S1, establishing a flight dynamics model of the helicopter, preliminarily determining the areas of the upper and lower horizontal tails to ensure that the longitudinal forward flight stability requirements of the helicopter are met, preliminarily determining the installation angles of the upper and lower horizontal tails to ensure that the attitude angle of forward flight and the load are within a reasonable range, and preliminarily determining the connection points of the upper and lower horizontal tails to ensure that the aerodynamic force distribution of the horizontal tail and the force borne by the horizontal tail and the tail section joint are reasonable; S2, establishing an interference calculation model comprising the rotor, the fuselage and the upper and lower horizontal tails of the helicopter, calculating and analyzing the interference flow field of the rotor on the upper and lower horizontal tails at each forward flight speed to determine the strong interference state of the rotor on the upper and lower horizontal tails; S3, obtaining the rotor wake tilt angle χ at the position of the upper and lower horizontal tails in the strong interference state; S4, adjusting and determining the longitudinal installation position of the root of the lower horizontal tail, so that the included angle between the line connecting the 1 / 4 chord line points of the upper and lower horizontal tails at the same spanwise position and the horizontal plane is equal to the rotor wake tilt angle χ; S5, keeping the total area of the upper and lower horizontal tails unchanged, adjusting the chord lengths of the upper and lower horizontal tails, so that the aerodynamic interference of the rotor on the upper and lower horizontal tails in the strong interference state is minimized.

5. A truss supported twin tail design method as claimed in claim 4, wherein, The method further comprises: S6, carrying out a scale model fuselage wind tunnel test: obtaining the fuselage aerodynamic characteristic data comprising the double-layer horizontal tail and the blade root through the scale model fuselage wind tunnel test, and calculating and evaluating the flight load and flight quality of the helicopter according to the above data; by adjusting the areas and installation angles of the double-layer horizontal tail, changing the fuselage aerodynamic characteristics, so that the flight load and flight quality of the helicopter meet the design requirements, and further determining the areas and installation angles of the double-layer horizontal tail supported by the truss.

6. A truss supported twin tail design method as claimed in claim 5, wherein, The method further comprises: S7, carrying out a rotor-to-fuselage interference test: capturing the strong interference state of the rotor on the double-layer horizontal tail in the transition speed range through the rotor-to-fuselage interference test, adjusting the chord lengths of the double-layer horizontal tail, the longitudinal installation position of the root of the lower horizontal tail and the connection points of the upper and lower horizontal tails, so that the aerodynamic interference of the rotor on the double-layer horizontal tail is minimized, and further determining the chord lengths of the double-layer horizontal tail supported by the truss, the longitudinal installation position of the root of the lower horizontal tail and the connection points of the upper and lower horizontal tails.

7. A truss supported twin tail design method as claimed in claim 6, wherein, The method further comprises: S8, flight test is carried out: the effect of the double flat tail with the truss support in the strong interference state on reducing the interference of the rotor on the double flat tail is verified through the flight test, and the parameters of the double flat tail configuration are optimized according to the flight test in the whole flight envelope, and finally the design parameters of the double flat tail with the truss support are determined.

8. A helicopter characterized by The helicopter is arranged with the double flat tail configuration with the truss support as claimed in any one of claims 1-3.

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