A method for tail rotor aerodynamic force prediction under rotor interference based on coupled momentum source and blade element theory

耦合动量源和叶素理论的旋翼干扰下尾桨气动力预测方法

¹ School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
² 飞行器基础布局全国重点实验室, 陕西 西安 710072 --> National Key Laboratory of Aircraft Configuration Design, Xi'an 710072, China
³ Jiangxi Hongdu Aviation Industry Group Co., Ltd., Nanchang 330021, China
⁴ National Key Laboratory of Science and Technology on Aerodynamic Design and Research, Xi'an 710072, China
⁵ Key Laboratory of Rotor Aerodynamics, China Aerodynamics Research and Development Center, Mianyang 621000, China
⁶ China Helicopter Research and Development Institute, Jingdezhen 333001, China

Received: 8 January 2025

Abstract

Due to the influence of slip flow and wake, the tail rotor of a helicopter may produce strong unsteady aerodynamic force in its main rotor interference flow field, which may affect the helicopter control and lead to structural failure. Although the unsteady flow field simulation method can capture the details of the flow field, the calculation amount is large. Therefore, this paper presents a fast method of tail rotor aerodynamic force prediction based on coupled momentum source and blade element theory. The momentum source model takes into account the disturbance of the flow field of a main rotor to that of a tail rotor. The induced velocity of the tail rotor is extracted from the flow field, and its quasi-steady aerodynamic force is solved iteratively with the blade element theory. In order to verify the accuracy of the method, this paper carries out the prediction of the tail rotor's aerodynamic characteristics under the main rotor's interference with different sideslip angles. In the range of 0° to 30° sideslip angles, the error of the tail rotor's average pull coefficient obtained with the fast prediction method is 2.31% to 4.50% compared with the wind tunnel experiment. Compared with the experiment, the error of the unsteady flow simulation method using the sliding grid is -4.50% to 1.20%, but the calculation amount of the experiment is only 9.61%. In the forward flight state of a small sideslip, regardless of whether the rotor slip sweeps the tail rotor, compared with the tail rotor's average pull predicted with the unsteady flow simulation method, the error of the fast prediction method is -6.19% to 6.15%. The average value of the unsteady pull coefficient of a single blade and the peak value of the first and second order blade passing frequency are close to those of the unsteady flow simulation method.

摘要

由于滑流和尾迹的影响, 直升机尾桨在旋翼干扰流场中可能会产生强烈的非定常气动力, 严重时会影响直升机操纵, 导致结构失效。非定常流场仿真方法虽然能够捕捉流场细节, 但计算量大。因此, 提出了一种耦合动量源和叶素理论的尾桨气动力快速预测方法。利用动量源模型考虑旋翼对尾桨流场的干扰作用, 提取尾桨诱导速度, 并通过叶素理论迭代求解尾桨的准定常气动力。为验证其准确性, 开展了不同侧滑角旋翼干扰下尾桨气动力特性预测, 在0°~30°侧滑角范围内, 快速预测方法得到的尾桨平均拉力系数相对风洞实验的误差为2.31%~4.50%, 非定常流场仿真方法相对实验的误差为-4.50%~1.20%, 但前者计算量仅为后者的9.61%。在小侧滑的前飞状态下, 不论旋翼的滑流是否扫掠尾桨, 相比于非定常流场仿真方法预测的尾桨平均拉力, 快速预测方法的误差为-6.19%~6.15%, 单片桨叶的非定常拉力系数的平均值、峰谷值、一阶和二阶叶片通过频率处的峰值都与非定常流场仿真方法接近, 验证了耦合方法的气动力特性预测精度。