IGTC-118 Behavior of Tip Leakage Flow in a Diagonal Flow Impeller with High Specific Speed(Organized Session III TIP CLEARANCE FLOW)

概要

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The behavior of tip leakage flow in a diagonal flow impeller with high specific speed has been investigated by analyzing experimental and numerical results. Velocity and pressure fields which were ensemble-averaged and phase-locked by the periodic multi-sampling technique were measured downstream of the impeller and on the casing wall, respectively, for various tip clearances at various flow rates. A Navier-Stokes flow simulation with a high-resolution upwind scheme was performed for a large tip clearance at a design flow rate. Near the casing wall, there is a very large accumulation of low energy fluids due to the tip leakage flow. In the inlet region of the impeller passage the tip leakage vortex is formed. At the aft part of the passage, however, the tip leakage vortex disappears, and no rolling-up of the tip leakage vortex is observed in the secondary flow field downstream of the impeller. In contrast to the axial flow impeller, as the tip clearance increases, and/or the flow rate decreases, the accumulation region of low energy fluids due to the tip leakage flow moves from the pressure side to the suction side.
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