Cavitating Flows of Varying Temperature Liquid Nitrogen in Converging-diverging Nozzle Free

The objective of this paper is to investigate the unsteady cavitating flows of varying temperature liquid nitrogen. Liquid nitrogen cavitating flows in a converging-diverging (C-D) nozzle are carried out with the temperature range from 68 K to 86K, the pressure in the tanks is within the range of 0.03 MPa∼0.30 MPa. The experimental results show that there are two typical cavitation dynamics in varying temperature liquid nitrogen, namely quasi-isothermal mode and thermo-sensitive mode. As the free-stream temperature increases, the cavity area increases to its maximum around the transition temperature and then significantly decreases. Further analysis indicates that the liquid/vapor density ratio D dominates the change of the cavitation dynamics when the temperature is below the transition temperature. The cavity tends to be mushier (smaller bubbles) and longer with the increasing temperature. However, the thermodynamic effects on cavitation, which could suppress the development of the cavitating flow, dominate the change of the cavitation dynamics when the temperature is above the transition temperature. The transition temperature of cavitating flows in liquid nitrogen is between 76 K∼78 K, and the transition temperature slightly increases with the increasing cavitation number.