Unsteady Numerical Investigation of Blade Tip Leakage,Part 1: Time-Averaged Results

摘要

In today's modern gas turbine engines, the region between the rotor and the stationary shroud has the most extreme fluid-thermal conditions in the entire turbine and is characterized by a periodically unsteady three-dimensional flowfleld. The purpose of the present work is to conduct an unsteady study of the tip leakage flow adjacent to the shroud in real gas turbine engines using an in-house industrial computational fluid dynamics code. Both time-averaged and time-dependent data for the velocity, temperature, and mass flow rate in the tip clearance region are presented in parts 1 and 2, respectively. In part 1, it was found that near the pressure side of the tip clearance region and near the blade tip on the suction side, the leakage flow is dominant, whereas opposing flows entering through the suction side dominate near the shroud and at the suction side. This opposing flow is the combined effect of the shroud relative motion and the crossflow originating from the adjacent blade passage on the suction side. A small recirculation region was observed above the rotor passage and was attributed to the blade-passage crossflow interacting with the high-pressure region found at the suction side of the blade. This high-pressure region is caused by the combined effect of the crossflow with the shroud boundary-layer flow interacting with the tip leakage flow inside the tip clearance region.