Dynamic Transfer Function Measurements for Cavitating Pumps

The Phase I effort demonstrated the feasibility of measuring cavitating inducer dynamic transfer functions using an upgraded Concepts NREC pump test facility. As there are no analytical tools or experimental facilities in the world today that can quantify a cavitating inducer?s dynamic transfer function, developing this capability is crucial for the safety, reliability and competitiveness of the American Space Industry. An innovative experimental technique that uses mappings of inlet and exit flow and pressure fluctuations to quantify a cavitating inducer?s dynamic transfer function is proposed. A cavitating inducer can be a source of instability in a rocket vehicle. Due to cavitation dynamics, inlet flow perturbations maybe amplified by the inducer resulting in very large flow and pressure fluctuations in the fuel system. The resulting dynamic couplings can lead to vehicle instability (POGO) as well as generate intense dynamic loadings on the turbopump. The feasibility of implementing the proposed measurement technique on an upgraded Concepts NREC water flow test loop was demonstrated in the Phase I effort. Implementation of the test loop upgrades and demonstration of the transfer function measurement technique on a scaled inducer with a historical pedigree will occur in the proposed Phase II effort.