Visual Experimental Study on Liquid-Nitrogen Cavitating Flow on NACA 66 Hydrofoil

Cavitation is one of the main causes of failure in rocket engine cryopumps. Based on a visual experimental platform for liquid-nitrogen (LN2) cavitating flow over a NACA 66 hydrofoil, morphology evolutions of the cavity cloud for different cavitation numbers are observed with a high-speed camera. The time-averaged pressure distributions in the cavitation zone are also measured, and the maximum temperature drop is derived from the pressure data by assuming the thermodynamic equilibrium in the cavitation zone. The attached cavitation length is dependent on the cavitation number, and the relationship is investigated by image analysis using the standard-deviation method. The shedding characteristics of the cavitation cloud of LN2 and room-temperature water are compared, and the mechanism is qualitatively clarified. The research results provide valuable experimental data, which are rare in this field, and help to understand the influence of cryogenic cavitation.