Study On Plasma Control Of Tip Clearance Flow

Plasma is a new flow control method that is suitable for controlling tip leakage flow of rotor blades due to its advantages of having a simple structure,having fast response,and needing no moving parts.A simplified model of coaxial rotating circular cylinder with circumferential pressure gradient is proposed to simulate the tip leakage flow.The momentum equation and mass conservation equation in cylindrical coordinate system are solved analytically,and the analytical solution of circumferential velocity and volumetric flow between circular cylinders is obtained.The volumetric flow rate of the leakage can be regarded as the sum of circumferential pressure gradient and coaxial rotation.The effects of changing the rotational speed and radius ratios between the inner and outer cylinders on the volumetric flow rate of the leakage are investigated.Increases in the rotational speed ratio will Increase the leakage volumetric flow rate,and increases the radius ratio will decrease the volumetric flow rate.The influence of different media and different temperature on the total volumetric flow rate is studied.The results show that the effect is mainly through changing the dynamic viscosity of the medium.The influence of rotation can be neglected in the medium with smaller viscosity,and the influence of circumferential pressure gradient can be neglected in the medium with larger viscosity.At the same time,the leakage flow between rotating cones is also studied.A two-dimensional model of the dielectric barrier discharge plasma is established using Fluent to explore the principles of plasma flow control.The model results show that plasma can control the flow by inducing a jet near the wall,the maximum induced velocity appears on the left side of the interface above the buried electrode,the induced velocity increases with increases in the excitation voltage.The effect of plasma excitation applied to the leading edge of the blade tip of an axial flow compressor is simulated numerically.The result shows that the plasma excitation injects energy into the leading edge of the blade tip to alleviate the blockage of the tip passage.With the increase of the compressor rotational speed,the effect of the plasma excitation becomes less obvious.The effects of plasma excitation on tip leakage flow in turbine cascades are investigated experimentally by analyzing the static pressure difference at both the pressure surface and suction surface of the blade tip of the turbine cascade end wall caused by plasma application.It is concluded that plasma can reduce the static pressure difference to a certain extent.A higher plasma excitation voltage will cause a greater reduction but the effect of the plasma becomes less obvious as the axial position is shifted backwards.