DESIGN OF A NOVEL VERTICAL TAKE-OFF AND LANDING FIXED-WING AIRCRAFT
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可垂直起降的固定翼飞行器兼顾了传统旋翼飞行器和固定翼飞行器的特点，既能实现垂直起降，又能通过飞行模式的转换实现高速高效的水平巡航。随着航空领域的快速发展，可垂直起降固定翼飞行器的种类逐渐增多，其中尾座式飞行器可以在仅使用一套动力系统且不添加复杂倾转机构的情况实现垂直起降、飞行模式转换及水平前飞，因此该构型在可垂直起降固定翼飞行器领域具有更重要的应用前景和研究价值。尾座式飞行器在飞行过程中存在复合飞行模式及模式间的转换，因此如何兼顾垂向飞行阶段的稳定性，倾转过渡阶段的快速性以及水平飞行阶段的高效性成为研究尾座式垂直起降固定翼飞行器的关键问题。 针对尾座式飞行器难以兼顾各阶段飞行效率的问题，本文提出了一种双翼布局与四旋翼构型相结合的布局形式，以该布局形式为基础开展对尾座式飞行器的设计研究工作。通过总体设计初步确定机翼与机身的结构参数，结合初选翼型，对该飞行器进行三维建模，并对初步模型进行纵向及横侧向的气动数值仿真。针对初步数值仿真结果表现出的升力系数及升阻比不满足设计要求的问题开展了对该无人飞行器的气动布局优化工作。 通过气动仿真分析，探究了不同机翼参数与机身形状对于飞行器气动特性的影响，通过增大展弦比及更换翼型，将该飞行器的最大升力系数和最大升阻比在初步构型的基础上分别提高了15.2%和46%，确保实现了失速速度小于11m/s，航时大于1h的设计指标。针对更换翼型后俯仰力矩特性变差的问题，本文提出了设置外翼段扭转角与增大外翼段后掠角相结合的俯仰力矩特性优化方法，将飞行器的低头力矩减至更换翼型后的52%。根据气动布局优化后的最终仿真结果分析可得，本文所设计的尾座式垂直起降固定翼飞行器能够很好的兼顾垂向飞行、倾转过渡、固定翼飞行三个阶段的飞行效率，同时具备纵向和横航向的稳定性，实现了设计阶段的目标。
Vertical take-off and landing (VTOL) fixed-wing aircraft synthesizes the characteristics of traditional rotary-wing aircraft and fixed-wing aircraft. It can not only achieve vertical take-off and landing, but also realize high-speed and efficient horizontal cruise through the conversion of flight modes. With the rapid development of aviation field, the types of VTOL fixed-wing aircraft have increased gradually. Among all kinds of VTOL fix-wing aircraft, the tail-sitter aircraft can realize vertical take-off and landing, flight mode conversion and horizontal forward flight using only one set of power system without adding complex tilting mechanism. Therefore, this configuration has more important application prospect and research value in the field of VTOL fixed-wing aircraft. There are multiple flight modes and inter-mode conversion in the flight process of tail-sitter aircraft. Therefore, how to take into account the stability in the vertical flight stage, the rapidity in the tilting transition stage and the high efficiency in the horizontal flight stage has become the key problem in the research of the tail-sitter VTOL fixed-wing aircraft. Aiming at the problem that it is difficult for tail-sitter aircraft to take into account the flight efficiency of every stages, this paper proposes a layout form that combines a biplane configuration and a quad-rotor configuration. Based on this layout form, the design and research work of the tail-sitter aircraft is carried out. The structural parameters of the wing and the fuselage were preliminarily determined through the overall design, combined with the preliminary selection of the airfoil, the three-dimensional modeling of the aircraft was carried out, and the longitudinal lateral aerodynamic numerical simulations are performed on the preliminary model. The influence of different wing parameters and fuselage shape on the aerodynamic characteristics of the aircraft was explored through the aerodynamic simulation analysis. By increasing the aspect ratio and changing the airfoil, the maximum lift coefficient and maximum lift-drag ratio of the aircraft are increased by 18.6% and 46% respectively on the basis of the preliminary configuration, ensuring that the stall speed is less than 12m/s and the flight time is more than 1h, which the design indexes were achieved. Aiming at the problem that the characteristics of pitching moment become worse after the replacement of airfoil, an optimization method of pitching moment characteristics combining setting the torsion Angle of outer wing segment and increasing the sweep Angle of outer wing segment was proposed in this paper, so as to reduce the bow moment of aircraft to less than 50% of that after the replacement of airfoil. According to the final simulation results after aerodynamic layout optimization, it can be concluded that the tail-type VTOL fixed-wing aircraft designed in this paper can well take into account the flight efficiency of the three stages of vertical flight, tilt-transition flight and fixed-wing flight, and at the same time has the stability of longitudinal and transverse direction, which achieves the goal of the design stage.
|Department||School of Innovation and Entrepreneurship|
于淇. 新型垂直起降固定翼飞行器设计[D]. 深圳. 南方科技大学,2021.
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