Enhancement of the Thermodynamic Suppression Effect of Cavitation in a Hydrofoil With a Slit

Abstract

The occurrence and growth of cavitation are suppressed in cryogenic fluids used as propellants for liquid rockets, and this phenomenon is called the thermodynamic suppression effect of cavitation. This effect is attributed to the temperature drop around the cavity caused by the latent heat of evaporation. Further, a method to suppress oscillation phenomena called cavitation instabilities by cutting off a part of the inducer blade (referred to as a slit inducer) has been proposed by the authors. Although the suitability effect was confirmed for suppressing the cavitation oscillation, there is a need to demonstrate that the slit does not inhibit the thermodynamic suppression effect of cavitation even when it is installed in the inducer of the liquid rocket turbopump. In this study, the thermodynamic suppression effect of cavitation is examined in an experiment with a NACA0009 hydrofoil with and without a slit in a hot-water cavitation tunnel as a preliminary step in the investigation of a slit inducer. The temperature drops and the distribution inside the cavity were measured by our direct temperature measurement method with unsteady temperature estimation method under T∞ = 90 °C to investigate the small difference in the thermodynamic suppression effect that does not appear in the cavity length. The expanded uncertainty of the temperature probe using thermistor is 17 mK. As a result, it was found that the cavity suppression amount in the region downstream of the slit inside the cavity increased under the condition of unsteady cavitation in the hydrofoil with a slit.