Research on transition corridor boundary of distributed propulsion VTOL fixed wing

分布式推进垂直起降固定翼的过渡走廊边界研究

School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China

Received: 22 December 2021

Abstract

The transition state is the most critical and dangerous state of the VTOL fixed wing aircraft in the whole flight process. In this paper, a transition corridor for a distributed propulsion VTOL fixed-wing aircraft is studied based on the lift characteristics of the wing and the power constraints of the power unit. Firstly, according to the sliding flow theory, the dynamic characteristics models of the lift fan system in the front part of the fuselage and the distributed duct system in the rear part of the fuselage were established by introducing the influence factor of the duct, and verified with the test data. Secondly, according to the lift characteristics of the wing, the transition curves of the aircraft at different angles of attack are calculated, in which the transition curves corresponding to the zero-lift attack angle and stall attack angle constitute the lift characteristics transition corridor of the distributed propulsion VTOL fixed-wing aircraft. Finally based on the dynamic performance of the power unit model, calculate the lift characteristic transition each state point in corridor corresponding power demand, according to the power limit of the lift fan system, distributed duct system and power unit total power limitation, get distributed to promote vertical take-off and landing a fixed wing aircraft power limitation in lifting features and power unit under the condition of complete transition corridor. The final results show that the minimum forward velocity is inversely proportional to the attack angle. The power required by the tail distributed duct system will exceed the limit when the aircraft is in low speed and small dip angle transition. For the power limit boundary required, the power limit condition of individual component is stricter than the total power limit condition. The research results of this paper can provide some reference for the transition corridor research of such VTOL fixed-wing aircraft, and on this basis, the subsequent work such as parameter sensitivity analysis and control system design of transition corridor can be carried out.

摘要

过渡状态是垂直起降固定翼飞行器在整个飞行过程中最关键和最危险的状态。针对一种分布式推进垂直起降固定翼飞行器, 基于机翼升力特性和动力单元需用功率的限制条件进行了过渡走廊研究。根据滑流理论, 引入涵道影响因子, 建立了机身前部升力风扇系统和机身尾部分布式涵道系统的动力特性模型, 并结合试验数据进行了验证; 根据机翼的升力特性, 计算得到飞行器在不同迎角下的过渡曲线, 其中零升迎角和失速迎角对应的过渡曲线组成了分布式推进垂直起降固定翼飞行器的升力特性过渡走廊; 基于动力单元的动力特性模型, 计算得到升力特性过渡走廊内各状态点对应的需用功率, 根据升力风扇系统需用功率限制、分布式涵道系统需用功率限制以及动力单元总需用功率限制, 得到分布式推进垂直起降固定翼飞行器在升力特性和动力单元需用功率限制条件下完整的过渡走廊。最终结果表明: 完成过渡所需要的最小前飞速度与过渡状态迎角呈反比; 飞行器在低速、小倾转角过渡时尾部分布式涵道系统的需用功率会出现严重的超限现象; 对于需用功率限制边界而言, 单部件的功率限制条件比总功率限制条件更加严格。文中的研究成果可以为这类垂直起降固定翼飞行器的过渡走廊研究提供一定的参考借鉴, 并可在此基础上进行过渡走廊的参数敏感性分析、控制系统设计、总体参数优化等后续工作。