等离子体气动激励对气膜冷却特性的影响

Effects of Plasma Actuation on Film Cooling Characteristics

采用大涡模拟方法研究了锯齿电极等离子体激励器气动激励对圆形孔和扇形孔平板气膜冷却效率和气动损失的影响。结果表明:锯齿电极激励器气动激励产生的动量注入效应促使边界层流体加速而提高了冷却气流向下游的延伸能力;锯齿电极激励器气动激励诱导的反肾形涡对削弱了肾形涡对的强度与尺度,减少了下游冷、热流体间的掺混,使得扇形孔的中心线和展向平均气膜冷却效率相对于圆形孔最大提高了130%和300%,肾形涡对控制区内的掺混总压损失显著减小;锯齿电极激励器气动激励导致气膜孔内的流动损失略有增大而使其成为影响总压损失的重要因素;锯齿电极激励器气动激励导致圆形孔的熵增升高了26%,但使得扇形孔的熵增减小了41%。

Large eddy simulations were conducted to investigate the influences of saw-tooth plasma actuator on the film cooling efficiency and aerodynamic loss of cylindrical and fan-shaped holes. The results show that thanks to the momentum injection effect of plasma actuation the boundary layer fluid accelerates, and thus the coolant extends further downstream. Moreover, the anti-kidney shaped vortex induced by the saw-tooth plasma actuator effectively weakens the strength of kidney shaped vortex, then the mixing process between coolant and crossflow is suppressed, the centerline and lateral-averaged film cooling efficiency of fan-shaped hole are therefore increased 130% and 300% in comparison to the cylindrical hole without plasma actuation, the mixing loss generated by the kidney shaped vortex is also greatly decreased. Since the plasma actuation strengthens the blocking effect of crossflow on the coolant, the flow loss in cooling holes increases and becomes an important source of the total pressure loss. Furthermore, due to the plasma actuation, the entropy creation of cylindrical hole is increased by 26%, but the entropy creation of fan-shaped hole is decreased by 41%.