Influence of natural gas composition and operating conditions on the phase change of dry gas seals for pipeline compressors

• The impact of the choking effect, turbulence effect and real gas effect of the natural gas is investigated. • The difference in phase change behavior of pure components of natural gas, binary and multi-component natural gas mixtures is compared. • The minimum inlet temperature to prevent phase change of the sealing medium is obtained based on the p - H diagram. Dry gas seal is critical component in pipeline natural gas compressor, with phase change between sealing faces being a major cause of failure. This paper focuses on spiral groove dry gas seals at 8–20 MPa, considering different sealing medium and real fluid effects. A thermohydrodynamic lubrication model is established, and solved using the finite difference method. The paper analyzes the differences in phase change behavior of pure components of natural gas, binary and multi-component natural gas mixtures . Based on the p - H diagram, obtain the minimum inlet temperature to prevent phase change of the sealing medium. The results show that CH 4 and N 2 are less likely to undergo phase changes, while C 2 H 6 and CO 2 have similar phase change behaviors. Heavier hydrocarbons are more prone to phase changes. Phase changes of binary or multi-component mixture primarily occur near the inner diameter of the sealing face or at the leakage outlet, with the gas mass fraction in the gas–liquid two-phase region usually exceeding 0.9. Under the parameters calculated in this paper, the minimum sealing face inlet temperatures to prevent phase change for a typical natural gas sample at inlet pressures of 12 MPa, 15 MPa and 20 MPa are approximately 278 K, 288 K and 298 K, respectively.