Comparison between the calculated subsonic inviscid three-dimensional flow in a centrifugal impeller and measurements

The paper reports the results of a comparison between measurements in centrifugal impellers and those from a fully three-dimensional inviscid calculation method based on Wu's (1952) theory, predicting the flow in turbo impellers and using the finite element method for solving the principal equations. Three impellers, identical except for shroud contours and inducer section blading, were used: impeller A (separated flow) having an impeller exit/impeller inlet velocity ratio of 0.6; impeller B (attached flow) a ratio of 1.0; and impeller C (attached flow) an accelerated velocity ratio of 1.4. Measured and calculated static pressure distribution around the blade surface on three stream surfaces (1/8, 4/8, and 7/8) of each impeller are presented. Results indicate that inviscid flow prediction methods for subsonic flow, even when formulated for fully three-dimensional flow, can be used with confidence only when the flow is not separated; the present technique yields good agreement with measured velocity profiles in the case of impellers with attached flow.