Tip flow control performance and mechanism of axial slots in a pumpjet propulsor

Abstract

In this study, a new method for controlling the tip leakage vortex of a pumpjet propulsor is developed by adding rectangular axial slots to the inner wall of the duct. The first objective of this study is to explore the control performance of the axial slots on the tip leakage vortex. The tip leakage vortex with axial slots is compared with that without axial slots using the Improved Delayed Eddy Simulation method. The comparison results indicate that the axial slots can effectively control the tip leakage vortex, significantly increase the vortex core pressure, and have a minor effect on the thrust and torque of the propulsor. The second objective is to analyse the control mechanism of the axial slots on the tip leakage vortex. By investigating the effects of the axial slots on the pressure and velocity distributions near the tip leakage vortex, the control mechanism of the axial slots on the tip leakage vortex can be divided into two stages. In the first stage, the axial slots reduce the backflow in the blade tip clearance and decrease the strength of the tip leakage vortex. In the second stage, when the tip leakage vortex is close to the rear of the axial slots, owing to the strong suction effect of the axial slots on the tip clearance flow, the axial slots reduce the concentration of the swirling flow of the tip leakage vortex and further increase the vortex core pressure.