PIV measurements of supersonic slot-film cooling with shock/cooling-film interaction
PIV measurements of supersonic slot-film cooling with shock/cooling-film interaction
复制标题
具有冲击/冷却膜相互作用的超音速槽膜冷却的 PIV 测量
DOI：
--
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
M. Klaas
中科院分区：
文献类型：
--
作者：
Pascal Marquardt;F. Michaux;M. Klaas
超音速槽膜冷却是一种很有前途的冷却概念，可用于降低发动机部件的表面温度。如果这些部件中存在激波，它们与冷却膜的相互作用可能会改变需要冷却的表面附近的流场的基本结构，这反过来可能会降低冷却效率。本文的研究范围是分析冷却油膜的喷射马赫数和冲击强度对激波/冷却-气膜相互作用的影响。在自由流马赫数Ma∞=2.45时，通过二维缝式喷嘴，在湍流边界层下分别喷射了两种不同的冷却液膜，其注入马赫数分别为1.2和1.8。β=5°和8°的气流偏转都会产生不同强度的冲击波，冲击到冷却油膜上。利用高速粒子图像测速仪对激波/冷却-气膜相互作用的流场进行了研究，分析了三种流型的时均速度场和雷诺应力分布。较高的喷射马赫数和较低的冲击强度相结合，表明冲击对冷却油膜的影响是适度的。降低喷注马赫数或增大激波强度都会导致大分离气泡的高度扰动流动。在这种情况下，冷却气膜和外部流动之间的热量和动量的湍流传输大大增加。将低冲击强度情况下的计算结果与大涡模拟结果进行了比较。在激波冲击位置附近的流动结构、激波诱导的层流缝隙边界层的转变以及湍流输运的增加等方面，本文的研究结果与数值模拟结果基本一致。
Supersonic slot-film cooling is a promising cooling concept for surface temperature reduction of engine components that experience high thermal loads. If shocks are present in these components, their interaction with the cooling film may change the fundamental structure of the flow field in the vicinity of the surfaces that require cooling, which in turn can reduce the cooling effectiveness. The scope of this study is to analyze the influence of the injection Mach number of the cooling film and the shock strength on the shock/cooling-film interaction. Two different cooling films with injection Mach numbers of Mai = 1.2 and 1.8 are injected beneath a turbulent boundary layer through a twodimensional slot nozzle at a freestream Mach number of Ma∞ = 2.45. Flow deflections of either β = 5° or 8° generate shock waves with different strength which impinge upon the cooling film. The flow field of the shock/cooling-film interaction is investigated by means of high-speed particle-image velocimetry, and the timeaveraged velocity fields and the Reynolds stress distributions are analyzed for three flow configurations. A high injection Mach number in combination with a low shock intensity shows moderate influence of the shock impingement on the cooling film. Lowering the injection Mach number or increasing the shock intensity leads to a highly disturbed flow with large separation bubbles. In these cases, the turbulent transport of heat and momentum between the cooling film and the outer flow is greatly increased. The results of the low shock strength cases are compared with large-eddy simulations. There is a reasonable agreement between the present study and the simulations with respect to the flow structure in the vicinity of the shock impingement position, the shock-induced transition of the laminar slot boundary layer, and the increase in turbulent transport.