Modeling of the Gas Dynamic Processes with Different Equations of State

Abstract

The work is devoted to the study of the features of gas-dynamic processes at the high pressures. The flows of air, hydrogen and water vapor are considered. The results obtained using the ideal gas equation and two real gas equations - van der Waals and Soave-Redlich-Kwong are analyzed. The comparison has been done on the numerical simulation results for the safety valve operation problem. The problem was solved in a three-dimensional non-stationary formulation using the finite volume method. Numerical solution method was built on the basis of the Godunov’s method. The results of a comparison of isotherms for each media are presented. Those are obtained using the considered equations of state in the regions when the gases thermodynamic parameters are changed. The influence of the gas model on the processes in the safety valve has been studied in detailsfor hydrogen. A detailed comparison of the local distributions of pressure, temperature, density, and flow velocity has been made. The complex impact of the flow parameters was studied using the integral characteristics - the gas-dynamic force acting on the disk and the gas flow rate. It has been found the gas-dynamic forces obtained within the framework of ideal gas model and the Soave-Redlich-Kwong gas are close to each other in magnitude and exceed the force for the van-der-Waals gas. However, the flow rate of ideal gas significantly exceeded that for both real gases. It is due to a twofold increase in density, which is not compensated by a decrease in the flow velocity. Thus, to obtain accurate data on the dynamic and velocity effects of gas flows on technical devices at high pressures it is necessary to use the real gas equations of state.