实际气体对T槽干气密封动态特性的影响

目前，针对干气密封的研究一般把气体处理为理想气体，但是在高压工况下，气体的实际行为与理想气体有较大差异。采用维里方程表达气体的实际行为，获得实际气体效应修正的气体润滑雷诺方程，利用小扰动法和有限差分法求解该雷诺方程，获得压力分布，进而获得气膜刚度和气膜阻尼等表征干气密封动态特性参数。针对T槽干气密封，以二氧化碳（CO₂）、氢气（H₂）和氮气（N₂）为例，分别分析了实际气体效应对T槽干气密封的气膜刚度和气膜阻尼等动态特性的影响，并与理想气体进行对比，结果表明：随着压缩数的增大，三种实际气体与理想气体的气膜刚度、气膜阻尼均增大。随着频率数的增大，实际气体与理想气体的气膜刚度增大，气膜阻尼减小。实际气体气膜刚度、气膜阻尼偏离理想气体气膜刚度、气膜阻尼的程度随着压缩因子Z偏离理想气体（Z=1）的程度增加而增加。对于CO₂ （Z<1），气膜刚度大于理想气体气膜刚度，而气膜阻尼小于理想气体气膜阻尼。对于H₂ （Z>1），气膜刚度小于理想气体气膜刚度，而气膜阻尼大于理想气体气膜阻尼。N₂（Z≈1） 的气膜刚度与气膜阻尼与理想气体近似相等。

Effect of real gas on dynamic performance of T-groove dry gas seal

Lubricating gas is generally considered as ideal gas in the study of dry gas seal. However, the behavior of real gas is quite different from that of ideal gas under high pressures. In this study, the virial equation was used to express the behavior of gas to obtain a Reynolds equation for gas lubricating, modified by the effect of real gas. The Reynolds equation was solved by perturbation method and finite difference method to obtain the pressure distribution, and the dynamic characteristic parameters of dry gas seal, such as gas film stiffness and gas film damping, were obtained. As to the T-groove dry gas seal, carbon dioxide (CO₂), hydrogen (H₂) and nitrogen (N₂) were taken as examples to analyze the influence of real gas upon the gas film stiffness and gas film damping of T-groove dry gas seal, which were compared with those of ideal gas. The results show that the gas film stiffness and gas film damping of the three real gases and ideal gas increase with the squeeze number. Gas film stiffness of the real gas and ideal gas increase with the increase of frequency number, while the gas film damping decreases. The deviations of the film stiffness and gas film damping of real gas from those of ideal gas increases with the derivation of compressibility number Z from ideal gas (Z=1). For CO₂ (Z<1), its gas film stiffness is larger than that of ideal gas, while the gas film damping is smaller. For H₂ (Z>1), its gas film stiffness is smaller than that of ideal gas, but the gas film damping is larger. For N₂ (Z≈1), both the gas film stiffness and gas film damping are approximately equal to those of ideal gas.