脉冲射流对环量控制翼型气动性能的影响

定常射流在大迎角下气动性能较差，借助脉冲射流能够有效改善大迎角下的气动性能，并减少射流所需质量流量。采用非定常数值模拟的方法进行了脉冲射流作用下的环量控制翼型气动特性计算和流场分析。总结了占空比和频率分别对时均升力和升力脉动幅值的影响趋势；分析了不同迎角下的脉冲射流流动机理；进一步指出了射流动量系数的影响规律，并借助脉冲射流和定常射流的叠加效应有效缓解了升力脉动现象。结果表明:低占空比、同等升力系数下，脉冲射流可大幅度减小质量流量，但升力脉动幅值较大；小迎角下随频率增大，升力系数先增大后减小，但整体变化幅度不大，大迎角下随频率增大，升力系数持续性增大；脉冲射流能够推迟失速迎角，扩宽环量控制技术的可用迎角，并且随动量系数增大，这种优势更加明显；借助脉冲射流与定常射流的叠加效应，能够有效缓解脉冲射流作用下的升力脉动现象，达到飞行使用条件。 

Effect of pulsed jet on aerodynamic performance of circulation control airfoil

The aerodynamic performance of steady jet is poor at high angle of attack. With the help of pulsed jet, the aerodynamic performance at high angle of attack can be effectively improved and the mass flow rate of jet can be reduced. The unsteady numerical simulation method is used to calculate the aerodynamic characteristics and analyze the flow field of the circulation control airfoil under pulsed jet. The effects of duty cycle and frequency on the amplitude of time-averaged lift and lift pulsation are summarized. The flow mechanism of pulsed jet at different angles of attack is analyzed. Furthermore, the influence law of jet momentum coefficient is pointed out, and the lift pulsation phenomenon is effectively alleviated with the help of the superposition effect of pulsed jet and steady jet. The results show that, under low duty cycle, the pulsed jet can greatly reduce the mass flow rate under the same lift coefficient, but the amplitude of lift pulsation is larger at the same time. At low angle of attack, the lift coefficient increases at first and then decreases with the increase of frequency, but the overall change is not obvious, and at high angle of attack, the lift coefficient increases continuously with the increase of frequency. The pulsed jet can delay the stall angle of attack and widen the angle of attack, and this advantage becomes more obvious with the increase of momentum coefficient. With the help of the superposition effect of the pulsed jet and the steady jet, the lift pulsation under the pulsed jet can be effectively alleviated and the flight conditions can be achieved.