单介质阻挡放电等离子体激励对平板气膜冷却性能的影响

Influence of Single Dielectric Barrier Discharge Plasma Actuation on Film Cooling Effect at Plain Surface

为了研究单介质阻挡放电(SDBD)等离子体激励对平板气膜冷却性能的影响,采用数值求解耦合等离子体电动激励力的雷诺时均Navier-Stokes(RANS)方程组的方法,利用已有的实验数据考核了等离子体线性化激励模型和数值求解方法的有效性,获得了6种归一化激励强度、5种归一化激励频率和3种吹风比条件下,存在SDBD等离子体激励时壁面的气膜冷却效率分布及其附近的流场结构,并与无等离子体激励的气膜冷却工况进行了对比。研究结果表明:与无SDBD等离子体激励时相比,施加SDBD等离子体激励显著提升了平板气膜冷却性能,抑制了气膜孔下游肾形涡对的发展,使近壁面流向速度梯度增大、流向速度峰值提升、冷气沿展向及流向的覆盖范围均扩大。当归一化激励强度由40增至140时,平板气膜冷却效率显著提高;当归一化激励强度为100时,中心线及展向平均气膜冷却效率的极值分别比无SDBD等离子体激励的工况提高了105%及200%。当归一化激励频率由1.25增至6.25时,平板气膜冷却效率也逐渐提升;与无SDBD等离子体激励的工况相比,当归一化激励频率为3.75时,中心线及展向平均气膜冷却效率极值分别提升了75%及100%。平板气膜冷却性能随吹风比的增大逐渐恶化;当吹风比由0.5增至1时,壁面中心线及展向平均气膜冷却效率的极值分别降低了23.9%及49.2%。

By solving the RANS equations coupled with plasma actuation forces,the influence of single dielectric barrier discharge(SDBD)plasma actuation on film cooling effect at plain surface was numerically investigated.With the experiment data,the reliabilities of linearized plasma force model and numerical methods were validated.Under six different dimensionless actuation strengths,five different dimensionless actuation frequencies and three blowing ratios,the film cooling effects on plain wall surface were predicted.The computed film cooling effectiveness distributions and flow structures near the film cooled surface with SDBD plasma actuation were compared with the cases without plasma actuation.The numerical results show that compared with the case without SDBD actuator,the film cooling effect on plain wall surface is significantly enhanced.With SDBD plasma actuation,the development of counter-rotating kidney vortex pair downstream the cooling hole is suppressed,resulting in a larger near-wall streamwise velocity gradient,higher peak value of near-wall streamwise velocity,and wider coolant coverage along both spanwise and streamwise directions,than the case without plasma actuation.As the dimensionless actuation strength increases from 40 to 140,the film cooling effect on plain wall surface is improved significantly.As the dimensionless actuation strength is equal to 100,the maximum centerline and laterally averaged film cooling effectiveness are increased by 105%and200%respectively,compared with the case without plasma actuation.As the dimensionless actuation frequency increases from 1.25 to 6.25,the film cooling effectiveness on plain wall surface is kept increasing.When the dimensionless actuation frequency is equal to 3.75,the maximum centerline and laterally averaged film cooling effectiveness on plain wall surface are higher than the case without plasma actuation by 75%and 100%respectively.As the blowing ratio increases,the film cooling effect on plain wall surface is decreased correspondingly.As blowing ratio increases from 0.5 to 1.0,the maximum centerline and laterally averaged film cooling effectiveness on plain wall surface are decreased by 23.9%and 49.2%,respectively.