Theoretic Analysis of the Effect of Carbon Dioxide Real Gas on the Performance of the T-Groove Dry Gas Seal

Abstract

Dry gas seals have widely used in many centrifugal compressors and other rotating machinery. The gas performance of the dry gas seal is generally regarded as an ideal gas when the gas seal is investigated, designed, and operated. However some real gases performance may be quite different from the ideal gas when the gas pressure is high. In this paper, the carbon dioxide (CO2) was taken as an example in some T-groove dry gas seal, and the virial equation of state, which expresses the effect of real gas, was used, and the finite difference method (FDM) was adopted to solve the Reynolds equation of gas lubrication. The effects of real gas on the opening force (Fo) and radial leakage (Q) of the T-groove gas seal had been obtained. The results show that the seal performance (Fo, Q) will be underestimated when the real carbon dioxide is considered as an ideal gas. In calculation conditions, Fo and Q were maximum underestimated 4.16% and 19.25% respectively when Po was 5MPa and ns was variable and the real carbon dioxide was considered as an ideal gas; Fo and Q were maximum underestimated 7.48%, and 29.25% respectively, when ns was 3000r/min and Po was variable and the real carbon dioxide was considered as an ideal gas.