Abstract
A technique for high-accuracy predicting performance curve instability in pumps and clarification of the phenomenon in order to control the instability are required for designing high performance pumps. We analyzed internal flow of a test mixed-flow pump by using Large Eddy Simulation (LES) and clarified that euler's head drop caused by stall near the tip of impeller blade is a dominant factor of this test pump's instability. When the head drops, stall fields cover whole blade passages. Angular momentum drop caused by the stall on leading edge exceeds angular momentum increment caused by decreasing in flow rate on trailing edge. The stall cell rotates between impeller blade passages every almost 20 revolution on the occasion of the head drop. The stall field in the blade passage grows caused by increasing attack angle, and the blade passage is recovered from the stall caused by decreasing pressure gradient and increasing flow rate.
