Investigation of Impeller Backface Cavity Flowfield Using CFD and a One-Dimensional Flow Solver

Abstract This article aims at the investigation of impeller backface cavity flowfield using Computational Fluid Dynamics (CFD) and one-dimensional flow solver for a representative backface cavity. For initial validation the test rig data from Hart and Turner [5 and 6] is employed at various leakage flows and inlet swirl ratios. For impeller backface cavity in consideration, rather than covering a wide range of impeller leakage flows, which is irrelevant for engine operations, different rotational speeds representing different phases of engine running conditions are varied. The cavity flowfield is composed of two flows entering the cavity, impeller leakage and Compressor Discharge Pressure (CDP) seal leakage flows. The flowfield displays the dominant character of torques induced by the stator and the rotor for the majority of the cavity, towards the lower radii radially inward flow starts to gain swirl and when CDP seal leakage flow mixes with this flow, swirl ratios reach nearly unity. A fraction of mixture flow leaves the cavity thru the outlet and remaining circulates at bottom left corner and gets pumped up by the backface surface.