等离子体气动激励复合横向槽结构提高气膜冷却效率的数值研究

Numerical Simulation on Improving Film Cooling Effectiveness with Plasma Aerodynamic Actuation Coupling Transverse Slot Structure

关键词:  等离子体气动激励  横向槽  肾形涡对  反肾形涡对  气膜冷却效率

Key words:  Plasma aerodynamic actuation  Transverse slot  Kidney-vortices  Anti-kidney-vortices  Film cooling effectiveness

摘要:

基于横向槽结构和等离子体气动激励的新型流场调节方法，采用RNG k-ε湍流模型，数值计算分析了常规圆形孔、带横向槽以及带等离子体气动激励等不同气膜冷却结构的流场特性、温度场特性和冷却效率，揭示了等离子体激励器复合横向槽新型气膜冷却结构的冷却机理及规律。结果表明:圆形孔气膜冷却结构，气膜孔出流与主流混合强烈，在流场中形成了肾形涡对，冷流被逐渐抬离壁面，热流被卷吸到冷流下方，壁面的冷却效果最差；冷流经过等离子体激励器的气动激励后，产生了反肾形涡对，使得肾形涡对的平均涡量减小了42.64%，同时诱导冷流贴壁流动；横向槽的存在使得气膜孔出流在展向分布更宽，更贴近壁面，肾形涡对的强度较弱；在横向槽和等离子体气动激励的共同作用下，反肾形涡对的强度最大，使冷流的展向分布区域更大并贴近壁面流动。与圆形孔气膜冷却结构相比，在吹风比M=1.0下，带等离子体激励器、带横向槽和“等离子体激励器+横向槽”等三种气膜冷却结构的全局平均气膜冷却效率分别提高了181.6%，73.5%和200.5%。

Abstract:

Based on the new methods of flow field adjustment，such as transverse slot structure and plasma aerodynamic actuation，the flow field characteristics，temperature characteristics and cooling effectiveness were analyzed for different film cooling structures: the common circle-hole，transverse slot structure and plasma actuator film cooling structure with RNG k-ε turbulence model. The cooling mechanism and law of plasma actuator & transverse slot structure were revealed. The results show that in circle-hole film cooling structure，kidney-vortices，which lifted the cooling flow and entrain the hot flow，was formed，therefore the cooling effectiveness was the lowest. In the plasma actuator structures，anti-kidney-vortices was formed and induced the cooling flow near to the wall，and average vorticity value of kidney-vortices decrease 42.64%. The film outflow distributes wider in lateral and more near to the wall because of the characteristics of transverse slot structure，the intensity of kidney-vortices is much lower as well. The anti-kidney-vortices reached its maximum，the film outflow distributes wider in lateral and more near to the wall under interaction of transverse slot and plasma actuator structure. Compared with the common circle-hole film cooling structure，the overall film cooling effectiveness of plasma actuator structure，transverse slot structure and plasma actuator & transverse slot structure improve 181.6%，73.5% and 200.5% respectively at blow ratio=1.0.