Abstract
The paper describes the results of recent experiments carried out in the Cavitating Pump Rotordynamic Test Facility for the dynamic characterization of cavitation-induced flow instabilities as simultaneously observed in the stationary and rotating frames of a high-head, three-bladed axial inducer with tapered hub and variable pitch. The flow instabilities occurring in the eye and inside the blading of the inducer have been detected, identified, and monitored by means of the spectral analysis of the pressure measurements simultaneously performed in the stationary and rotating frames by multiple transducers mounted on the casing near the inducer eye and on the inducer hub along the blade channels. An interaction between the unstable flows in the pump inlet and in the blade channels during cavitating regime has been detected. The interaction is between a low frequency axial phenomenon, which cyclically fills and empties each blade channel with cavitation, and a rotating phenomenon detected in the inducer eye.
Highlights
Hawaii, Maui absolute and relative frames by multiple transducers mounted on the casing near the impeller eye and on the inducer hub along the blade channels
The RAPDUD inducer tested in the present campaign is a three-bladed, high-head, axial inducer with tapered hub and variable pitch
The static pressure rise has been measured between IPT1 and OPT1 stations and cavitation in the inducer flow has been suppressed by properly adjusting the inlet pressure well above the inception conditions
Summary
Turbopump-fed rocket engines represent the most weight-effective solution for launch propulsion systems of modern space vehicles that make use of large amounts of liquid propellants In these applications the turbopumps are required to develop both the high head and superior suction performance necessary to supply the propellant stored in low-pressure, light-weight tanks to the engine’s combustion devices that operate at very high pressures. Present experiments focused on refining the characterization of the cavitation phenomena developing inside the inducer blade channels and their interactions with the flow instabilities occurring in the impeller eye Earlier experiments to this purpose, like those carried out by Yoshida and his collaborators ([38], [39], [40]), suitably multiplexed at the frequency of the impeller rotation the measurements of pressure transducers flush-mounted on the impeller casing in order to extract the information on the flow behavior in the blade channels. The pressure taps of the hub-mounted transducers have been located at several stations along the midline of the blade channels from the leading to the trailing edges of the blades for better investigating the nature and behavior of the flow instabilities developing or extending deep inside the impeller
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