倾转三旋翼飞行器地面效应风洞试验

倾转旋翼飞行器在近地悬停或低速前飞时有明显的地面效应,对飞行器的气动载荷有强烈影响。针对倾转三旋翼(TTR)飞行器的地面效应问题,采用0.5 的缩比模型,在低速回流式开口风洞中设计了可移动地面平台,模拟TTR飞行器悬停和低速前飞时的离地高度,利用杆式天平测量机体所受载荷大小并使用粒子图像测速(PIV)技术捕捉机体下方的动态流场。试验结果表明:当TTR飞行器悬停离地高度在1.25倍旋翼直径以下时,地面效应影响显著,机体受到的最大上载荷约为旋翼总推力的4%,并观测到明显的涡旋喷泉流现象;在低速前飞状态,受旋翼尾流和前向来流影响,相对于悬停状态机体所受上载荷明显减小,喷泉流中心后移。试验结果对TTR无人飞行器动力系统选择,控制増稳系统设计以及借助地面效应优势提高承载能力具有一定参考价值。

Ground effect test of tri tilt-rotor aircraft in wind tunnel

Tilt-rotor aircraft has an obvious ground effect in hover or low-speed forward flight near ground, which has a strong effect on the aircraft aerodynamic loads. According to the ground effect problems of tri tilt-rotor (TTR) aircraft, a 0.5-scale TTR aircraft model is used in tests, a movable plat is designed to simulate the height of TTR vehicle above the ground in low-speed opening wind tunnel, a rod balance is used to measure the loads on the body and particle image velocimetry (PIV) is applied to the shot of dynamic flow field underneath the body. The test results show that with the influence of ground effect, the maximum upload on the body is about 4% of the thrust of total rotors when the TTR aircraft hovers height is less than 1.25 times of the rotor diameter, and the vortex fountain flow phenomenon is observed; in low-speed forward flight, with the influence of rotor wake flow and forward flow, the upload on the body significantly reduces with respect to the hover state, and the fountain flow center shifts afterward. The test results provide a reference for the TTR unmanned aerial vehicle power system selection, design of control systems and improvement of carrying capacity by using the advantage of ground effect.