基于因果网络分析的扩压叶栅波浪形前缘控制机理

Flow control mechanism of diffuser cascade with wavy leading-edge based on causal network analysis

分离与涡运动是限制压气机性能提升的关键,波浪形前缘结构能有效扩大压气机工作范围。在扩压叶栅上实施波浪形前缘造型,通过多目标优化算法构造以牺牲微小设计点性能为代价,大幅度降低失速点损失的波浪形前缘造型。采用数据挖掘方法——因果网络分析探究在波浪形前缘控制参数的变化下,扩压叶栅内部流场流动机制。优化结果表明当幅波比在0.05~0.15区间时,有更适合于流动控制的前缘涡涡量强度,且能在牺牲最少设计点性能的情况下,使失速点损失获得大幅下降。通过因果网络模型与流场分析验证,从涡运动的角度出发,波浪形前缘产生前缘涡对,前缘涡对的发展通过不同途径削弱了通道涡和尾缘涡流的发展;从分离的角度出发,波浪形前缘通过改变前缘气流不均匀度与二次流动能,改善低能流体堵塞来减弱角区分离所引起的损失。

Separation and vortex motion are key factors limiting the performance improvement of compressors,while the wavy leading-edge can effectively expand the working range of the compressor.This study implements the wavy leading-edge shape on the diffuser cascade,and uses a multi-objective optimization algorithm to construct a wavy leading-edge that significantly reduces the stall point loss at the expense of minimum design point performance.A data mining method,causal network analysis,is used to investigate the flow mechanism of the internal flow field of the diffuser cascade with variation in the wavy leading-edge control parameters.The optimization results show that the strength of the leading-edge vortex pairs increases as the amplitude-wave ratio decreases,and that the stall point loss can be significantly reduced at the expense of minimum design point performance with the amplitude-wave ratio range within 0.05-0.15.The causal network model and flow field analysis verify that,from the vortex motion perspective,the wavy leading-edge generates leading-edge vortex pairs,and the development of the leading-edge vortex pairs weakens that of the channel vortex and trailing-edge vortex flow through different ways;from the separation perspective,the wavy leading-edge weakens the loss caused by the corner region separation by changing the leading-edge airflow inhomogeneity and secondary flow energy and improving the low-energy fluid blockage.