高速飞行复合式直升机旋翼受上洗时的驱转特性

Driving rotation characteristics of a compound helicopter's rotor undergoing upwash in high-speed flight

为研究高速飞行时复合式直升机旋翼受上洗时的驱转特性,在已有的直升机飞行性能模型基础上建立复合式直升机配平模型。以X3直升机为样例,探讨在旋翼受上洗流作用的驱转状态下升力分配和旋翼变转速对旋翼和直升机飞行性能的影响。研究表明:旋翼受上洗流作用时,从气流中吸收的能量随速度增加而增多,旋翼阻力功率增大。上洗流作用下的桨盘叶素扭矩分布与低速时的不同,产生驱转扭矩的区域明显增加,阻转扭矩较高的区域由后行侧变为前行侧。减小机翼安装角会降低机翼的升力占比,使旋翼阻力功率增加,对旋翼吸收气流能量有利,提升受上洗流作用时旋翼和直升机的性能。速度为400 km/h时,机翼安装角为8°的旋翼阻力功率比安装角为10°时高11.2%,旋翼和直升机升阻比分别增加了35.7%和2.6%。中高速飞行时,过度降低旋翼转速会导致机体抬头,旋翼吸收的气流能量增加。速度大于340 km/h后,机体保持水平,旋翼阻力功率减少,降旋翼转速不利于气流提供能量。然而,高速飞行时复合式直升机旋翼转速降低有利于减少旋翼功率消耗、提升飞行性能。

To study the driving rotation characteristics of a compound helicopter's rotor undergoing the upwash in high-speed flight,a compound helicopter trim model is established on the basis of an existing helicopter flight perfor-mance model.With a helicopter example similar to x helicopter,the effects of lift share and variable rotor speed on the flight performance of the rotor and helicopter are analyzed in the driving rotation state undergoing the upwash.The results show that the energy absorbed from the airflow increases with the increase of speed due to the upwash,and the rotor drag power increases.The torque distribution is different from that in low speed flight.The blade elements that produce the driving torque increase significantly,and the area with larger resistance torque shifts from the retreat-ing blade to the advancing blade.Decreasing the incidence angle of the wing reduces the proportion of the wing lift,which results in an increase in the rotor drag power.This is beneficial for the rotor to absorb energy from the airflow and improve the performance of the rotor and helicopter as the rotor undergoes an upwash flow.At 40o km/h,the ro-tor drag power with the wing incidence angle of 8°is 11.2%higher than that of 10°,and the lift-to-drag ratios of the ro-tor and helicopter increase by 35.7%and 2.6%,respectively.In medium-or high-speed flight,excessive reduction of the rotor speed causes the fuselage to pitch up,and the energy absorbed from the airflow by the rotor increases.As the flight speed is larger than 34o km/h,the fuselage remains horizontal,and the rotor drag power is reduced.Reduc-ing the rotor speed is not beneficial for the airflow to provide energy.However,reducing the rotor speed of the com-pound helicopter in high-speed flight is beneficial for reducing the rotor power consumption and improving the flight performance.