临近空间摆线桨低雷诺数非定常流动机理研究

The development of high-efficiency propulsion system is one of the key technologies to develop the near space airship. Cycloidal propellers can obtain higher propulsion efficiency than traditional propeller at low Reynolds number, which is expected to greatly improve the performance of the propulsion system of near space airship. In this project, accurate unsteady numerical simulation methods are used to simulate the unsteady flow of pitching airfoil at low Reynolds number and investigate the flow mechanism of near space cycloidal propeller. The research are mainly consist of: (1) Firstly, considering the particularity of low Reynolds number unsteady flow, transition models for unsteady flow separation and Low Reynolds number turbulence model considering rotation effect will be studied; (2) Secondly, dynamic Stall Characteristic and Unsteady Flow Mechanism of Pitch Airfoil at Low Reynolds Number will also be investigated; (3) Thirdly, flow Mechanism and Flow Field Structure Evolution Mechanism of Pitching airfoil and blades with Low Reynolds Number in Rotating Motion will be studied; (4) Finally, unsteady Flow of near space Cycloidal Propeller with Multi-blade Coupling Interference will be discussed, then the influence of different parameters on the aerodynamic characteristics of cycloidal propeller in will be analyzed. Through the study of this project, an in-depth understanding of the unsteady flow mechanism of cycloid propellers can be formed, and theoretical basis for the design of high efficient near space cycloidal propeller will be provided.

高效推进器研制是实现临近空间飞艇长时驻空的关键技术之一。摆线桨在低雷诺数下可获得比螺旋桨更高的推进效率和工况适应范围,有望大幅提升临近空间飞艇推进系统性能。项目拟针对摆线桨低雷诺数非定常流动尚待揭示的关键问题，在提高流动求解精度的基础上，揭示多种非定常效应对摆线桨气动特性的影响及耦合作用，阐述摆线桨低雷诺数高气动效率形成机理，内容包括：（1）针对低雷诺数非定常流动特殊性，开展适用于非定常分离流动的转捩判断模型以及考虑旋转效应的低雷诺数湍流模型研究;（2）研究俯仰振荡翼型低雷诺数动态失速特性和非定常流动机理;（3）研究俯仰振荡翼在旋转运动中的低雷诺数流动机制和流场结构演化机理;（4）研究摆线桨多桨叶耦合干扰下的非定常流动机理；分析不同参数对临近空间摆线桨气动特性影响规律。通过项目研究，为临近空间摆线桨设计提供理论指导，推动我国临近空间飞艇高效推进系统研制及创新发展。

临近空间是跨接航空和航天的新领域，临近空间科学探索与开发利用对我国实现创新发展战略具有重大意义。高效推进器研制是实现临近空间飞艇长时驻空的关键技术之一。摆线桨在低雷诺数下可获得比螺旋桨更高的推进效率和工况适应范围,有望大幅提升临近空间飞艇推进系统性能。项目针对摆线桨低雷诺数非定常流动尚待揭示的关键问题，在提高流动求解精度的基础上，揭示了非定常效应对摆线桨气动特性的影响及耦合作用，阐述了摆线桨低雷诺数流动机理。针对低雷诺数非定常流动的特殊性，开展了适用于非定常流动的转捩模型及低雷诺数湍流模型研究，采用嵌套网格开展数值模拟，提高计算收敛性或计算精度，并通过算例对比验证了数值方法的有效性；研究了俯仰振荡翼型低雷诺数动态失速特性和非定常流动机理，对翼型厚度、俯仰轴位置等参数对流动特性和气动特性的影响进行了分析；研究了俯仰振荡翼在旋转运动中的低雷诺数流动机制和流场结构演化机理，分析了等效弯度效应对俯仰振荡翼流场及气动特性的影响;研究了无自由来流和有自由来流情况下摆线桨多桨叶耦合干扰下的非定常流动机理，分析了桨叶运动过程中的动态特性和相互影响；研究了桨叶数、俯仰角等不同参数对临近空间摆线流场、瞬时合推力、时均推力、瞬时扭矩、时均扭矩、功耗以及桨叶气动力的影响规律。本项目研究成果可为临近空间摆线桨设计提供一定的理论指导，推动我国临近空间飞艇高效推进系统研制及创新发展。