含杂质二氧化碳实际气体干气密封性能研究

Effects of the real-gas characteristics of carbon dioxide with impurities on the dry gas seal performance

基于EOS-CG模型和GERG-2008模型计算含杂质二氧化碳混合气体的密度,基于CO2-Pedersen模型计算混合气体的黏度。利用模型计算数据拟合获得含杂质二氧化碳混合气体密度、黏度与压力的关系式,用以描述混合气体的实际行为以及黏度随压力变化的规律。采用有限差分法求解稳态雷诺方程,得到了纯二氧化碳和含杂质二氧化碳干气密封开启力、泄漏率以及气膜刚度,并分析了杂质对二氧化碳干气密封性能(开启力、泄漏率、气膜刚度)的影响。考虑的变量有端面平均线速度、气膜厚度、进口温度以及进口压力等。结果表明:当进口压力为15.26 MPa,进口温度为363.15 K,线速度为74.030 m/s,气膜厚度为3.05μm时,含杂质二氧化碳干气密封开启力和泄漏率都小于纯二氧化碳干气密封开启力和泄漏率,且杂质含量越多,差别越明显;杂质对二氧化碳干气密封开启力、泄漏率、气膜刚度的影响随端面平均线速度的增大而增大;对泄漏率、气膜刚度的影响随气膜厚度的增加而减小;对开启力、泄漏率、气膜刚度的影响随进口温度的增大而减小;对开启力的影响随进口压力的增大先减小,再增大,最后减小,对泄漏率的影响随进口压力的增大先增大后减小,对气膜刚度的影响随进口压力的增大先减小后增大。

Based on the EOS-CG model and GERG-2008 model, the density of the mixed carbon dioxide gas containing impurities is calculated, and the viscosity of the mixed gas is calculated based on the CO2-Pedersen model. The relationship between density, viscosity and pressure of pure carbon dioxide and mixed gas are obtained by fitting the calculated data of these models to describe the real gas behavior and the law of viscosity changing with pressure of pure carbon dioxide and mixed gas. The steady-state Reynolds equation is solved by using the finite difference method, and the opening force, leakage rate and film stiffness of the dry gas seal lubricated by pure carbon dioxide or carbon dioxide with impurities are obtained, and the influence of impurities on the performance(opening force, leakage rate, film stiffness) is also analyzed. The variables considered include the average linear velocity of the end face, film thickness, inlet temperature, and inlet pressure. The results show that when inlet pressure is 15.26 MPa, and inlet temperature is 363.15 K, and linear velocity of the end face is 74.030 m/s, and film thickness is 3.05 μm, both the opening force and leakage rate of the dry gas seal lubricated by carbon dioxide with impurities are lower than those of pure carbon dioxide dry gas seal. The more impurities content, the more obvious the difference. The effect of impurities on the opening force, leakage rate, and film stiffness of the carbon dioxide dry gas seal increases with the increasing of the averaged linear velocity of the end face. The effect on the leakage rate and film stiffness decreases with the increasing of the film thickness. The effect on the opening force, leakage rate, and film stiffness decreases with the increasing inlet temperature. The influence on the opening force of carbon dioxide dry gas seal decreases firstly, then increases, and finally decreases with the increasing of the inlet pressure,and the influence on the leakage rate of carbon dioxide dry gas seal increases firstly and then decreases with the increasing of the inlet pressure, and the influence on the film stiffness decreases firstly and then increases with the increasing of the inlet pressure.