Unsteady Numerical Investigation of Blade Tip Leakage, Part 2: Time-Dependent Parametric Study
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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 2 of the present work, the effect of tip clearance height, inlet turbulence intensity, inlet total temperature, and rotor angular velocity on the tip leakage flow pattern is investigated. It is found that the separation bubble is always present near the pressure side of the blade tip at all times and that its size varies with flow conditions. For smaller tip clearance heights, the mass flow rate entering the tip clearance region is lower, due to the smaller area, which results in a smaller separation bubble. At higher stagnation temperatures, the separation bubble size is also reduced, due to the flow's higher velocity, which allows the leakage flow to dominate over the bubble growth. Also, at lower angular velocities, the effect of the shroud relative motion is reduced, and so more leakage flow is allowed to enter, thereby suppressing the growth of the separation bubble. Copyright 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
