扫频式射流对设计工况压气机叶栅流动分离影响的数值研究

高负荷压气机中的大尺度流动分离是导致其性能下降的主要原因,通过数值方法研究了扫频式射流控制角区分离、减小气动损失的效果,并以模型方程代替实际射流器,讨论了扫频式射流的基本控制参数对压气机叶栅流场控制效果及气动性能的影响。结果表明:扫频式射流使得流场呈现出稳定的周期性变化趋势,且存在一个扫频频率,使得超过该频率后的控制效果趋于稳定;合理选择扫频激励参数对实现流动分离的控制至关重要。在本文的方案中,采用较小的扫频射流角和射流流速能取得较好的控制效果,而更大的最大扫频摆角能强化这种控制效果,时均总压损失最大减小6.1%;扫频式射流能够在更大范围内提高吸力面边界层低能流体的动能,以更好地限制角区分离沿叶高方向发展,从而改善对角区分离的控制效果。

Numerical Study for Effects of Sweeping Jets on Separation in a Compressor Cascade at Designed Condition

Large scale separation is responsible for the performance deterioration of highly-loaded compressors. Numerical method was employed to study the effect of the sweeping jet to manage the corner separation and reduce aerodynamic losses. The actual sweeping jet actuator was replaced with governing equations to provide further discussions of the influence of several governing parameters on the aerodynamic performance enhancement and flow field improvements. The results supported the following conclusions. Firstly, a steady periodic variation existed under the flow field with sweeping jets. A governing excitation frequency could be found that with excitation frequencies larger than the governing excitation frequency, the total pressure loss reduction in the compressor cascade with sweeping jets turned out to be similar. Besides, appropriate excitation parameter arrangements were crucial to the control of separation. The sweeping jets with a smaller excitation jet angle to the suction surface and a smaller excitation jet velocity obtained better flow control performance against the corner separation. The effectiveness of the flow control was enhanced with larger sweeping angle with a 6.1% reduction of total pressure loss at most. Finally, the aerodynamic improvements mechanism with sweeping jet were pointed out to be larger excited region of low momentum fluids in the suction side boundary layer and stronger restriction of the development of the corner separation toward blade spanwise.