Impeller Fluid Forces

Abstract

This paper addresses the issue of the steady and unsteady forces which may be imparted to a pump impeller by the through flow. The historical trend to increase the power density and speed of turbomachines has inevitably led to an increase in the number of fluid/structure interaction problems because the fluid forces scale like the square of the speed and thus become increasingly important relative to the structural strength. The present paper focuses on the radial forces acting on the impeller of a pump. Under the sponsorship of NASA, the authors have, over the past few years, conducted an extensive investigation of these forces and the associated hydrodynamically induced rotordynamic coefficients. A new facility, called the Rotor Force Test Facility was designed and constructed for the experimental component of this program. Measurements of the forces and rotordynamic coefficients have been made for a range of different impeller and volutes and include tests with the impeller of the high pressure oxygen turbopump (HPOTP) in the Space Shuttle Main Engine. Furthermore, tests have been conducted with different leakage flow geometries and, with different levels of pump cavitation. The paper will summarize these experimental measurements and the results of some theoretical analyses.

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