Investigation Of The Effect Of The Tip Leakage Flow Control On Compressor Rotating Instability

Rotating instability is one of the aerodynamic instabilities in the compressor.The investigation of the effect of the tip leakage flow control on compressor rotating instability is essential for the further study on the mechanism of the rotating instability and the improvement of the compressor stability.The present thesis is based on a one-stage low-speed axial compressor.Experiments and time-accurate simulations were applied,combined with the dynamic pressure acquisition,spectrum analysis,modal decomposition and numerical analysis,to investigating the influence of the active control of tip injection and passive control of casing treatment on the frequency and modal characteristics of the rotating instability and unsteady flow of the rotor tip region.So the aim is to explain the flow mechanism of the two type of control strategies influencing the rotating instability.Specifically,the main research of this study are as follows:(1)The one-stage low-speed axial compressor casing was treat with the arc-curve skewed slot and tip injection system respectively.The experimental and numerical results showed that the two type of control strategies effectively improve the stall margin of the compressor.(2)Experiments were conduct with the arc-curve skewed slot casing treatment.By analysing the pressure fluctuation of the tip region with spectrum analysis,modal decomposition and cross-correlation,the results showed that the passive control is an effective strategy to suppress the rotating instability.(3)Two different injection massflow were select in the active control experiments.Using the spectrum analysis,modal decomposition and cross-correlation to analysis the dynamic pressure signal,and finding the massflow of the injection had limited impact on the rotating instability.(4)The numerical results of casing treatment showed that the arc-curve skewed slot had influence on the unsteady flow of the rotor tip region.The trajectory of the tip leakage vortex was changed,and the onset of the tip leakage flow was postponed.The detailed analysis results indicated that the low energy flow which blocks the tip region was removed by the reversed flow in the slot and the flow condition of the tip region was improved.(5)The numerical analysis of tip injection showed that tip injection had effect on the unsteady tip clearance flow.Moreover,the flow condition was improved more effectively with 0°axial injection angle,which push the axial movement of the tip leakage flow to avoid circumferential developing over the adjacent blade.At the same time,above the 80% span of the blade,the load and the total pressure loss were reduced.