悬停状态剪刀式尾桨气动/噪声特性优化分析

建立了一套基于CFD(computational fluid dynamics)方法和FW-H(Ffowcs Williams-Hawkings)方程的剪刀式尾桨气动噪声预估技术和组合优化算法的尾桨外形参数设计方法。基于嵌套网格方法采用雷诺平均Navier-Stokes(RANS)方程作为尾桨流场求解控制方程,采用了一套适用于剪刀式尾桨悬停气动特性模拟的高效CFD方法。在流场分析的基础上,采用FW-H方程预测剪刀式尾桨在典型观察位置处的气动噪声。分别在控制总距以及控制拉力系数不变的情况下,以提高尾桨悬停效率同时降低气动噪声为目标,对剪刀式尾桨的剪刀角和轴间距两个主要外形参数进行优化设计。将基于拉丁超立方(LHS)方法和径向基函数(RBF)的代理模型方法与遗传算法过程相结合,建立了一种有效的组合优化算法。结果表明:剪刀角和轴间距的不同组合可以通过削弱桨-涡干扰现象从而实现降低旋翼桨-涡干扰噪声的目的。在当前的计算状态下,优化得到的剪刀式尾桨的悬停效率比常规尾桨高16%,其平均声压级比常规尾桨降低了2.3 dB。 

Optimization analysis for aerodynamic noise characteristics ofscissors tail rotor in hover

A structure parametric design method of scissors tail rotor was established, in combination with areodynamic noise prediction technique based on CFD(computational fluid dynamics)/FW-H(Ffowcs Williams-Hawkings) equations and combinatorial optimization algorithm. The embedded grid method was developed to predict the flowfield of scissor tail rotor in steady flow. Based on the Navier-Stokes (RANS) equations, a high-effciency CFD simulation method was adopted for aerodynamic characteristics prediction of scissor tail rotor in hover. Based on the previous flowfield calculations, FW-H equations was established to predict the aerodynamic noise of scissor tail rotors. Then, to improve the hover efficiency and reduce the aerodynamic noise, optimization design for structural parameters of scissor tail rotor (scissors angle and shaft spacing) with constant thrust coefficient and constant pitch was conducted respectively. The genetic algorithm and surrogated model based on latin hypercube sampling (LHS) design and radial basis function (RBF) were combined as a hybrid optimization technique. The noise reduction mechanism of the tail rotor was obtained by these results. And the results show that, different combinations of scissors angle and shaft spacing can reduce the blade-vortex interaction phenomenon to cut down rotor blade-vortex interaction noise. Under the current calculation state, compared with conventional rail rotor, the hover efficiency of the optimized tail rotor increased by 16%, and the average sound pressure level decreased by 2.3 dB.