Study On Temperature Stratification Of Cryogenic Fluid During Outflow And Cryogenic Cavitation Characteristic

Thermal stratification is found in cryogenic tank that contains cryogenic fluid such as liquid hydrogen and liquid oxygen, which may lead to pressure rising in the tank, and it will not only make the quality of emission fluid worse, but also produce potential dangerous during outflow. Cavitation phenomenon can easily occur when fluid flows within pipes at very high speed, which can destroy the pipes seriously. So it is of significance to study temperature characteristic of cryogenic fluid during outflow and cryogenic cavitation phenomenon, which is helpful to improve the safety of cryogenic fluid applications and performance of energy power plants that cruise on liquid oxygen and hydrogen fuel. In order to make a more particular knowledge of thermal stratification and cavitation of cryogenic fluid, numerical studies were performed on a liquid oxygen horizontal tank during pressurization discharge with electrical heating and liquid hydrogen cavitation through elbow pipe. Main jobs in this paper are as follows:(1) Conducting a numerical simulation on a small liquid oxygen horizontal tank during discharging by electrical heating based. The flow field and temperature distribution of liquid oxygen inside the tank were obtained, it is found that the existence of the heater will have obvious inhibition effect on the development of thermal stratification.(2) To take thermodynamic effect into account, the thermodynamic effect term was developed based on Rayleigh-Plesset bubble equation by solving the equations of heat diffusion and bubble equilibrium, and a modified cryogenic cavitation model considering thermodynamic effect was presented. Comparing numerical simulation on isothermal condition and condition considering thermal effect were conducted to verify the modified model and analyze the role thermodynamic effect plays on cryogenics cavitation.(3) Numerical studies were performed on liquid hydrogen cavitation through elbow pipe, relationship between liquid hydrogen cavitation and inlet velocity, and outlet pressure were studied, the structure of cavity, distribution of temperature and pressure inside the cavity, and length of cavity for different inlet velocity and outlet pressure were obtained. Cases for different turbulent viscosity ratios were simulated to make sence of the influence turbulent viscosity ratios play on liquid hydrogen cavitation, relation between turbulent viscosity ratio and thermal effect was analyzed. Differences in liquid hydrogen cavitation were studied while the angles of elbow pipe were changed. The results show that before the flow of liquid hydrogen comes to steady state, the inlet velocity and outlet pressure have obvious impacts on cavitation process. To increase the inlet velocity or lower the outlet pressure can both strengthen the cavitation process. The turbulent viscosity ratio has fewer effects on cavitation process of liquid hydrogen, but increase of turbulent viscosity ratio can enhance the thermal effect. Besides, it is also found that pipe bending Angle is smaller, the cavitation occurs more easily, and the degree of cavitation development are more fully.