Gamma Densitometry Technique for Quantifying Void Fraction in Cavitating Flows

Cavitation in liquid rocket engine turbopumps can degrade performance, damage hardware, and generate vibration that impacts the entire vehicle. Many types of cavitation can occur within the operating envelope, and their presence complicates the design process. Cavitation models remain invalidated due to the lack of direct measurements of cavitation. Presence of cavitation is typically indirectly inferred through head falloff and measurements of casing static pressure and temperature. An experimental tool that can measure void fraction and directly quantify cavitation would improve the understanding of cavitation and allow validation computational tools. ORBITEC proposes to develop a gamma tool to quantify in-situ void fractions in turbopump systems. A novel twin-detector setup will yield a data rate of hundreds of Hz, much faster than the state of the art. Specialized calibrations will allow the technique to take measurements through moving blades. Phase I work will develop the twin detector gamma tool, establish its metrics through controlled laboratory tests, and perform proof-of-concept tests in Aerospace Corporation’s cavitation test facility. Phase II work would be an extensive experimental program including tests on controlled bubbly flow and hydrofoil and inducer testing in the Aerospace cavitation test facility.