Numerical Study of the Flow in Axial Cascade with Tip Clearance
LI Wei, WANG Guo qiang (School of Naval Architectre & Ocean Eng., Shanghai Jiaotong Univ., Shanghai 200030, China)
An artificial compressibility approach was applied for the numerical simulation of the turbulent flow field in an axial cascade with tip clearance. The numerical results indicate that the process of the tip vortex formation is delayed with the decreasing of the tip clearance. Its strength weakens rapidly. The range of its influence becomes smaller. The core of the tip vortex moves from the suction surface to the pressure surface along the direction of the flow. The coefficient of the pressure at the blade surface is reduced to some extent due to the existence of the tip clearance, especially near the tip of the blade. The effect of the vortex becomes smaller at the region of center and the root of the blade when the clearance decreases. The existence of clearance will result in the decreasing of the main stream and increasing of the secondary velocity near the tip of the blade obviously. The significant influence upon the characeteristics of the flow occurs when the clearance is from 2% chord to 5% chord.