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

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 CH₄ and N₂ are less likely to undergo phase changes, while C₂H₆ and CO₂ 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.