纳秒脉冲气动激励无人机流动控制风洞试验

等离子体流动控制作为一种新型的主动流动控制技术,可显著提升飞行器的气动性能。采用纳秒脉冲气动激励进行了某型无人机流动分离控制实验。实验结果表明:纳秒放电和毫秒放电的激励电压几乎相等,但是纳秒放电产生的电流(30A)比毫秒放电电流(0.1A)大得多;纳秒脉冲气动激励在流场中诱导产生近似向上的冲击波,最大诱导速度不超过0.5m/s;纳秒放电的快速温升效应在静止空气中诱导产生冲击波,冲击波的持续时间约为80μs,传播速度约为380m/s;当激励电压大于一定阈值时,纳秒脉冲气动激励使得该型无人机上表面的流动分离得到抑制,临界失速迎角从20°提升至27°,最大升力系数增大11.24%。探究放电频率对流动控制效果的影响规律,结果表明:最佳激励频率是使得施特劳哈尔数为1的频率值;在附面层流动控制方面,纳秒脉冲气动激励较毫秒脉冲气动激励更加有效;纳秒脉冲等离子体流动控制的主要机制是冲击效应,在高速流动控制中,冲击效应比动力效应更加有效。

A Wind Tunnel Experimental Investigation on Flow Control of UAV with Nanosecond Pulse Pneumatic Actuation

Being a new type of active flow control technology, the plasma flow control can significantly improve the aerodynamic performance of aircraft. In this paper, the flow separation control of a UAV is studied by nanosecond plasma aerodynamic excitation. The experimental results show that the nanosecond discharge and the millisecond discharge are almost equal in excitation voltage, but the current generated by nanosecond discharge (30 A) is much larger than that generated by millisecond discharge (0.1 A). The induced effect of nanosecond plasma is similar to an upward shock wave produced in the flow field, and the maximum induced velocity is less than 0.5 m/s. The rapid temperature rise effect of nanosecond discharge induces a shock wave in the still air. The shock wave lasts about 80 microns and travels at a speed of about 380 m/s. Withthe nanosecond plasma aerodynamic excitation being used, when the excitation voltage is greater than a certain threshold value, the flow separation on the suction surface of the UAV can be suppressed. The critical stall Angle of attack can be increased from 20° to 27°, and its maximum lift coefficient increases by 11.24%. Furthermore, the optimal excitation frequency of nanosecond plasma aerodynamic excitation is the value to make the dimensionless numbers 1. In the boundary layer flow control, the nanosecond plasma aerodynamic excitation is more effective than the millisecond plasma aerodynamic excitation. The main mechanism of nanosecond plasma flow control is impact effect. The impact effect is more effective than the dynamic effect in high speed flow control.