倾转旋翼机机翼向下载荷的计算方法及参数影响分析

Calculated method and parametric effect investigation of wing download of tiltrotor aircraft

针对悬停和前飞时旋翼下洗流对机翼的气动干扰影响,建立了机翼向下载荷的计算模型。该模型中,旋翼在机翼处产生的诱导速度以及对机翼干扰的旋翼尾迹边界基于Weissinger-L升力面理论和自由尾迹方法计算,以考虑倾转旋翼桨叶的大负扭转和尖削带来的较大三维影响,机翼表面流则区分为弦向流及展向流,以分别计算向下载荷。以缩比的V-22模型旋翼为算例,计算了悬停时旋翼下方的下洗速度分布和机翼的向下载荷,与可得到的实验结果进行了对比,验证了计算模型的有效性。然后,应用该计算模型,研究了襟翼偏角、旋翼倾转角、前飞速度、旋翼/机翼间距等参数对机翼向下载荷的影响。结果表明:机翼的襟翼偏斜角对有效减小机翼向下载荷有重要作用,随旋翼从悬停向前飞倾转,机翼向下载荷减小。

A calculated model for predicting wing download of the tihrotor in hover and forward flight was given according to the aerodynamic interaction effect of the rotor downwash flow on the wing. In the model, the calculations of induced velocities by rotor at wing and the boundary of tihrotor wake were based on the Weissinger-L lifting-surface theory and free-vortex method so as to represent better the 3-D effect of the tihrotor blade with large twist and taper. The surface flow over the wing is classified into the chordwise flow and spanwise flow so as to calculate their individual contribution on the wing download. The V-22 tiltrotor model was taken as examples, and the downwash velocity distribution below tihrotor and the download on wing in hover were calculated and compared with available experimental data to show the capability of the method. Then, using the model, the effects of the parameters such as flap angle, rotor tilting angle, forward-flight velocity and space between rotor and wing on the wing download were investigated. The analytical results show that the flap angle of wing has important effect on reducing wing download and the wing download decreases with the tilting of rotors from hover to forward flight.