Numerical calculation and analysis of aero-acoustic characteristics of tilt rotor in different tilt angles

不同前倾角度倾转旋翼噪声数值计算分析

National Key Laboratory of Helicopter Aeromechanics, China Helicopter Research and Development Institute, Jingdezhen 333000, China

Received: 28 March 2023

Abstract

The numerical calculation model for the aero-acoustic analysis of a tilt rotor was established by combining the free wake method and the FW-H (Ffowcs Williams-Hawkings) equation. The numerical method was validated by using the tilt rotor′s aero-acoustic test results. The aero-acoustic characteristics of dual tilt rotors that take into account the force and moment trim of an aircraft in its typical transition path were calculated. The unsteady air load of a rotor blade and its noise data in different observational positions were acquired. The acoustic directivity and sound pressure level of the tilt rotor in its different tilt angles were analysed. The results show that: the acoustic directivity characteristics of an isolate tilt rotor and dual tilt rotors were quite different due to the superposition and offset during noise radiation; the sound pressure level first increases and then decreases along with the rotor′s tilt angle; the maximum sound pressure level occurs at the tilt angle of 30 degree; the acoustic directivity and sound pressure level in different tilt angles vary due to multiple factors such as the Mach number at the rotor tip, air load and rotor orientation.

摘要

基于自由尾迹结合FW-H(Ffowcs Williams-Hawkings)方程的方法建立了倾转旋翼气动噪声计算模型, 并采用倾转旋翼模型噪声试验数据验证了计算分析方法的有效性。选取典型过渡路径, 进行考虑配平的倾转双旋翼气动噪声特性计算, 获得了旋翼桨叶剖面非定常气动载荷以及不同测点气动噪声等计算结果, 分析了倾转旋翼在不同前倾角下噪声指向性和噪声声压级的变化。结果表明：由于双旋翼噪声在传播中的叠加和抵消, 倾转双旋翼和孤立单旋翼的噪声指向特性存在较大的不同; 倾转旋翼噪声随前倾角增加总体上呈现先增加后减小的变化趋势, 在前倾角30°附近噪声最强; 不同前倾角下噪声声压级和指向性的变化与旋翼桨尖马赫数、气动载荷和桨盘角度等多种因素相关。