合成射流控制高速扩压叶栅二次流的数值模拟

数值研究了合成射流控制高速扩压叶栅角区分离，并揭示其推迟分离、降低损失的作用机理。研究发现:合成射流可以显著改善叶栅内流场的时空结构，叶栅出口时均总压损失系数最大降低19.8%，静压系数也提高了近8.8%。合成射流通过周期性地吹/吸气有效控制角区分离，吹气阶段的高动量射流流体增大了吸力面附面层及角区流体的能量，吸气阶段则借助于附面层抽吸作用有效减少了高熵、低能流体的堆积，从而增强了角区流体抵抗流向逆压力梯度的能力、并推迟流动分离，且吸气阶段的流动控制效果明显更好。射流角度和射流动量是影响合成射流作用效果的重要参数，近切向的合成射流有利于向附面层注入动量，增大射流动量也有助于增强流动控制效果。析因设计研究表明，射流角度的影响效应更为显著，但与射流动量之间并不存在交互作用。 

Numerical simulation of secondary flow control on high-speed compressor cascade with synthetic jets

A simulation study on the use of synthetic jets for the corner separation control on a high-speed compressor cascade was conducted. The mechanisms of the active flow control on delaying flow separation and reducing flow losses were analyzed in detail. Results showed that the space-time structure of the flow field in the blade passage was improved significantly with a maximum loss reduction of 19.8%, while the static pressure rise increment of 8.8% was gained. By periodically adding or removing fluid to or from the boundary layer, synthetic jets could effectively control the corner separation. In the blowing phase, synthetic jets remarkably increased the energy level of the blade suction surface boundary layer and the corner region, while the accumulation of high entropy and low energy fluid towards the corner region was effectively suppressed in the suction phase. The above two contributed to enhancing the resistance to streamwise adverse pressure gradient and thus reducing flow separation. It was worthy to mention that the flow control effect during the suction phase was much more pronounced. Both jet angle and jet momentum were important parameters for the flow control effect. When the jet convected tangentially downstream, the flow control was very efficient in injecting high momentum fluid into the boundary layer, accounting mainly for the resistance to streamwise adverse pressure gradient. In addition, increasing the jet momentum could further improve the cascade time-averaged aerodynamic performance. Factorial design studies indicated that the effect of jet angle was much more pronounced than that of jet momentum, while there was no evidence to support the interaction between jet angle and jet momentum.