Dynamic Transfer Function Measurements for Cavitating Pumps

There are no analytical tools or experimental facilities in the world today that can quantify the dynamic transfer function for a cavitating inducer. The goal of this research is to fill this void. An innovative experimental technique is proposed where by a cavitating inducer's dynamic transfer function is quantified by mapping the flow and pressure fluctuations at the inducer exit as a function of harmonic perturbations at the inlet. A cavitating inducer can be a source of instability in a rocket engine. 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 technique on the Concepts NREC water flow test rig will be demonstrated in Phase I of the project. Implementation of the technique and inducer transfer function identification will occur in Phase II. The proposed dynamic transfer function characterization methodology is applicable to any high energy density turbomachine subject to impeller induced flow instabilities, such as boiler feed pumps or re-injection pumps and compressors.