Overall design scheme of light tilting rotorcraft

Abstract

The invention belongs to the field of aviation, and discloses an overall design scheme of a light tilting rotorcraft. The overall design of the light tilting rotorcraft comprises weight distribution and flight performance calculation, isolated rotor design and performance analysis design, wing design, horizontal tail and vertical tail design, aircraft fuselage design and the like. The light tilting rotorcraft designed by the invention can realize vertical take-off and landing, hovering and flying in any direction, has the characteristics of light weight and capability of carrying people, meets the future requirements of continuously increasing civil market requirements and gradually opening low-altitude airspace, and has higher use value.

Description

Technical Field

[0001] This invention belongs to the field of aviation and discloses an overall design scheme for a lightweight tiltrotor aircraft. Background Technology

[0002] Traditional single-rotor helicopters suffer from many drawbacks: the rotor needs to simultaneously provide lift, thrust, and the force required to control the helicopter; shock waves can occur on the advancing blades at high forward speeds, and dynamic stall can occur on the retreating blades. This makes it difficult for traditional single-rotor helicopters to achieve high speeds. Tiltrotors, through their unique structural design, can achieve vertical takeoff and landing and hovering; simultaneously, in fixed-wing mode, the rotor nacelle tilts forward, at which point the rotor acts like a propeller, generating forward thrust to achieve high-speed forward flight. However, currently, existing tiltrotor aircraft are all heavy or medium-sized, and there are no lightweight tiltrotor aircraft, making it difficult to meet the increasing demands of the civilian market. Therefore, it is essential to develop a lightweight tiltrotor aircraft design, and we propose a general design scheme for this purpose. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an overall design scheme for a lightweight tiltrotor aircraft.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A general design scheme for a lightweight tiltrotor aircraft includes: weight distribution and flight performance calculation, isolated rotor design and performance analysis design, wing design, horizontal and vertical tail design, and fuselage design.

[0006] Further, the weight of each system of the tiltrotor aircraft is parametrically modeled to establish a weight distribution and subsystem weight analysis model that meets the characteristics of a lightweight tiltrotor aircraft. A power calculation model for the lightweight tiltrotor aircraft and a flight performance calculation model for helicopter mode are established using momentum theory and blade element theory. A flight performance calculation model for aircraft mode is established by introducing drag characteristics and the relationship between engine fuel consumption rate and speed.

[0007] Furthermore, the weight analysis model and flight performance calculation model are combined using a linear weighting method. The NSGA-II algorithm is adopted, with weight efficiency and flight performance as objective functions, to establish an overall parameter optimization model for a lightweight tiltrotor aircraft. The initially determined overall parameter scheme for the lightweight tiltrotor aircraft is optimized to determine the optimal overall scheme for the lightweight tiltrotor aircraft.

[0008] Further design was carried out on the rotor twist angle distribution, chord length distribution and blade airfoil configuration. The aerodynamic performance of the isolated rotor was numerically simulated using CFD software with nested meshes.

[0009] The further wing airfoil is NACA 65(4)-421, with an upward dihedral angle of 5° and a forward sweep angle of 4°.

[0010] Furthermore, the tail volume method was used to design the geometric parameters of the tail fin. A T-tail was adopted, and the airfoils for the horizontal and vertical tails were selected as NACA2415 and NACA0018, respectively. Referring to the general aircraft fuselage design method, a human body data model was established, and the fuselage parameters were designed in detail in combination with the characteristics of the light tiltrotor aircraft. The aerodynamic characteristics of the wings, tail fin and fuselage were numerically simulated using CFD software.

[0011] The beneficial effects of this invention are as follows:

[0012] 1. A design scheme for the overall parameters of a four-seat lightweight tiltrotor aircraft is provided, which is beneficial to the design of lightweight tiltrotor aircraft, meets the needs of low-altitude development, and has practical application value.

[0013] 2. An overall parameter optimization model is provided, and the optimization parameters are selected based on weight efficiency and the required power in both vertical and horizontal flight states, which improves the evaluation indicators such as the aircraft's economy and effectiveness. Attached Figure Description

[0014] Figure 1 Schematic diagram of fuel ratio balance method

[0015] Figure 2 Schematic diagram of weight distribution model

[0016] Figure 3 Diagram for overall parameter optimization Specific Implementation

[0017] In the embodiments, the design requirements for the lightweight tiltrotor aircraft are shown in Table 1:

[0018] Table 1 Performance Indicators of Four Light Tiltrotor Aircraft

[0019]

[0020] The overall parameters of the light tiltrotor aircraft were initially determined by combining the "statistical analysis method" and the "prototype design method". After evaluating the main flight performance and analyzing the relevant parameters, the overall parameters of the light tiltrotor aircraft were preliminarily determined as shown in Table 2.

[0021] Table 2 Overall Parameters of Light Tiltrotor Aircraft

[0022]

[0023]

[0024] The total weight of the lightweight tiltrotor aircraft was determined using the fuel ratio balance method, the flowchart of which is shown below. Figure 1 As shown, the rotor parameters, wing parameters, and engine power have been preliminarily estimated.

[0025] The weight distribution model for tiltrotor aircraft is calculated using the AFDD weight model, such as... Figure 2 As shown. The takeoff weight W0 of a light tiltrotor aircraft is determined by its empty weight W. empty Fuel weight W fuel and mission payload W payload Composition, including the mission payload W payload and fuel weight W fuel The weight can be determined according to design requirements. Therefore, the most important aspect of weight analysis for light tiltrotor aircraft is the analysis of the empty weight. Based on the layout and characteristics of light tiltrotor aircraft, the empty weight can be divided into three main parts for analysis: propulsion system weight, structural weight, and system and equipment weight. The propulsion system of a light tiltrotor aircraft consists of the engine system, fuel system, and braking system. The structural weight includes the rotor, fuselage, tail, landing gear, engine nacelles, etc. The system and equipment weight model includes the flight control system weight, hydraulic system weight, and other system weights. The flight performance calculation model includes vertical flight performance (hovering ceiling, vertical climb rate) and forward flight performance (lift-drag characteristics, maximum forward speed), as well as range and flight time.

[0026] After completing the weight distribution model and the flight performance model of the lightweight tiltrotor aircraft, optimization design can be carried out. The optimization method uses the NSGA-II algorithm, and the process is as follows: Figure 3 As shown, five main overall parameters are selected as optimization variables: rotor radius R, rotor solidity σ, blade tip speed variation coefficient ΔΩR, wing area S, and fuel mass W. fuel ,Right now:

[0027] X=[R,σ,ΔΩR,S,W fuel ] T

[0028] The optimization model is constrained by the presence or absence of ground effect hovering ceiling H. h Maximum vertical climb rate V ⊥max The maximum level flight speed Vmax, range L, and flight time T are calculated. The optimization objectives are weight efficiency Z and the power required P for hovering at an altitude of 2000 meters in vertical flight mode. rh Power required P at an altitude of 2000 meters and a forward speed of 500 km / h in horizontal flight mode rf The comparison before and after optimization is shown in Table 3:

[0029] Table 3 Comparison of results before and after optimization

[0030]

[0031]

[0032] After completing the overall optimization, the distribution of blade twist angle and blade chord length for the lightweight tiltrotor aircraft was designed. CFD was used for aerodynamic performance calculations. Then, the wing and other components were designed, with the wing airfoil being NACA 65(4)-421, anhedral angle of 5°, and forward sweep angle of 4°. The conventional tail design, including the horizontal and vertical tail, was carried out using the tail capacity method. The design parameters are shown in Table 4.

[0033] Table 4 Tail fin shape parameters

[0034]

[0035]

[0036] The fuselage design adopts a tadpole-shaped form as its basic shape, and the dimensions are shown in Table 5.

[0037] Table 5. External Dimensions of the Airframe

[0038]

[0039] CFD was used to calculate the aerodynamic performance of the wings, tail, and fuselage.

Claims

1. A general design scheme for a lightweight tiltrotor aircraft, characterized in that, include: Weight distribution and flight performance calculations; isolated rotor design and performance analysis; wing design; Horizontal and vertical tail design; Aircraft fuselage design, etc.

2. The overall design scheme of the lightweight tiltrotor aircraft according to claim 1, characterized in that: The weight of each system of the tiltrotor aircraft is parametrically modeled to establish a weight distribution and subsystem weight analysis model that meets the characteristics of a lightweight tiltrotor aircraft. A power calculation model for the lightweight tiltrotor aircraft and a flight performance calculation model for helicopter mode are established using momentum theory and blade element theory. A flight performance calculation model for aircraft mode is established by introducing drag characteristics and the relationship between engine fuel consumption rate and speed.

3. The overall design scheme of the lightweight tiltrotor aircraft according to claim 1, characterized in that: The rotor twist angle distribution, chord length distribution, and blade airfoil configuration were designed. The aerodynamic performance of the isolated rotor was numerically simulated using CFD software with nested meshes.

4. The overall design scheme of the lightweight tiltrotor aircraft according to claim 1, characterized in that: Design the wing airfoil, dihedral angle, and forward sweep angle.

5. The overall design scheme of the lightweight tiltrotor aircraft according to claim 1, characterized in that: The tail volume method was used to design the geometric parameters of the tail fin, and the airfoils of the horizontal and vertical tail were selected. Referring to the general aircraft fuselage design method, a human data model was established, and the fuselage parameters were designed in detail in combination with the characteristics of the light tiltrotor aircraft. The aerodynamic characteristics of the wing, tail fin and fuselage were numerically simulated using CFD software.

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