Numerical Investigation Of Loss Characteristics For A Dimpled Compressor Rotor Cascade

With the development of modern aero engines,higher requirements for compressor efficiency and load are put forward.But the increase of load brings greater separation and loss,which in turn restricts the performance of the compressor.The roots of air compressed are often in complex flow conditions,and the root zone is at the starting point of separation.The accumulation of low-energy fluid is serious and the loss is large.The passive flow control technology-the dimpled cascade,can effectively improve the blade loss near the root and restrain the development of the boundary layer.In this paper,the flow characteristics of the original cascade with different flow incidence angles and mach numbers are studied by using the CFD method,and the mechanism of the loss is analyzed.First,the numerical method is verified by experiments,and the reliability of the numerical method is verified.It is found that the mechanism of the dent in the dimple is analyzed.It is found that the vortex induced external fluid into the dimple increases the turbulent kinetic energy in the dimple,and the flow ability of the wall is enhanced,and the effect of "rolling bearing" on the gas air contact reduces the friction loss.The dent increases the loss near the exit end of the cascade,but the wake loss of the exit part is significantly reduced,and the total loss of the exit section decreases.After the calculation,the parameters of the dimple are changed,including the dimple location,the depth of the dimples,the ratio of the depth to the diameter of the dimples and so on.The influence of the change of the geometric parameters on the loss characteristics of the cascade is analyzed.It is found that the position of vortex core in the dimple changes in the dimple when the geometric parameters of the dimple change,and the flow condition in the downstream of the dimples is changed.By analyzing the loss characteristics of the outlet,it is determined that the best position of the dimple is the chord length of 75%?100%,the best depth of dimple is 0.2mm,and the depth to diameter ratio of dimple is 1/4.Finally,the variable conditions of the original cascade and the dimpled cascade are analyzed.The variable conditions include the incoming angle and the incoming machnumber.By analyzing the surface streamline and the loss characteristics of the outlet section under the variable conditions,it is found that the total loss of the cascade outlet section is lower only at the partial incidence angle,and the total loss of the section is reduced under all calculated mach numbers.The loss characteristics of dimple cascade under variable conditions are summarized,and the application value of dimple drag reduction technology is proved.