Study On Unsteady Flow Field Characteristics And Flow Control Of Compressor Under Supersonic Flow Condition

The new generation of high-performance compressors needs to be developed to lower losses,and wider and stable operating ranges.Therefore,it is of great significance to conduct in-depth exploration and research on compressors with higher single-stage pressure ratio under supersonic flow conditions.Under supersonic conditions,shock waves appear in the flow passage of the compressor,and the shock wave has a good supercharging effect.However,excessive shock wave and flow separation caused by the shock wave/boundary layer interaction(SWBLI)will bring about a large flow loss.Which also has a high degree of unsteady characteristics,in order to gain a deeper understanding of the unsteady flow field characteristics,get the inherent mechanism of flow control,need to further study the characteristics of unsteady flow in the blade passage,and find a feasible flow control solutions.In this paper,firstly we use the unsteady method to calculate the post-flow step model,and compare the unsteady simulation results with the experimental results to verify the reliability of the numerical method.Use this method to calculate the twodimensional compressor cascades,it is found that the suction surface of the blade is not only a high-loss region but also has strong unsteady characteristics.Through the frequency spectrum analysis,it is found that the dominant frequency of the measurement point of the SWBLI's separation zone is f=6784Hz.The dominant frequency of the downstream measuring point is mostly below 9000 Hz.By using the POD method,f=6634 Hz is the dominant frequency of the unsteady(second and third modes)of the flow field.In order to choose an effective flow control scheme,different jet flow-control schemes were carried by steady-state calculations.We found that when the jet width is 3.5 mm,the jet position is at x/ c(28)0.65 and the angle of jet flow is 64°,which is the best flow control scheme.Unsteady calculations were used to study the flow control of twodimensional cascade,Two schemes of jets include pulsed jets and constant jets.The total pressure loss factor of 0.0854 for the constant jet scheme is reduced by 10.3% compared with the prototype loss,and the total pressure loss factor for the pulsating jet is 0.0884,which is a 9.8% reduction compared to the equivalent constant jet scheme.Through POD analysis,it can be known that the jet flow controls can turn the kinetic energy of the fluid more into the mean flow field,so that the kinetic energy of the fluid can be more concentrated in the mode with lower orders and the flow field is more orderly.The jet flow controls will also cause the vortex of the downstream flow field to converge to the lower modes,increasing the order of the flow field.To a certain extent,the jets also reduce the flow separation caused by the channel's normal shock wave and the pressure surface of the blade.In this respect,the effect of the constant jet is more obviously.