Turbomachinery Rotor Forces: Final Report

Abstract

The overall objective of this contract was to experimentally and theoretically evaluate the fluid-induced forces, both steady and unsteady, acting upon an impeller of a centrifugal pump, and to investigate impeller blade-diffuser vane interaction in centrifugal pumps with vaned radial diffusers. Knowledge of the steady and unsteady forces, and the associated rotordynamic coefficients, is required to effectively model the rotordynamics of high speed turbopumps such as the High Pressure Oxygen Turbopump (HPOTP) and the High Pressure Fuel Turbopump (HPFTP) of the Space Shuttle Main Engine (SSME). Under the sponsorship of this contract, an extensive investigation of these forces and rotordynamic coefficients using different impellers in combination with volutes and vaned diffusers, and axial inducers has been conducted. These rotor forces are global, i.e., they result from the pressure distribution acting upon the complete impeller. Local forces and pressures are also important in impeller-diffuser interaction, for they may cause cavitation damage and even vane failure. Thus, in a separate investigation, impeller wake, and impeller blade and diffuser vane pressure measurements were made. This research program was begun on October 30, 1978, and completed August 30, 1988. A special test facility was designed and constructed for this work. In what follows the nature of the rotordynamic forces is discussed, the experimental facility is described, and measurements of unsteady forces and pressures are reported together with a brief and incomplete attempt to calculate these flows. A summary of all publications and reports issued under this contract is included.

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