Groove shape effects on the performance of dry gas seals in supercritical CO 2 centrifugal compressors

Abstract

Supercritical CO₂ (SCO₂) centrifugal compressors are pivotal components in next-generation high-efficiency power cycles (e.g., Brayton cycles), enabling greater than 50% thermal efficiency and compact power block designs essential for sustainable energy systems. This study addresses a critical reliability challenge by optimizing dry gas seal (DGS) groove designs for these compressors. Using validated 3D CFD simulations, incorporating k-ω SST turbulence model and Redlich-Kwong real gas equation of state, the performance of four industrial groove geometries (spiral, oval, fish-tail, and tree-type) are evaluated. Results demonstrate that the tree groove minimizes leakage (29.7% reduction vs. spiral) through tortuous flow paths, directly supporting emissions control and operational economy in power cycles. Conversely, spiral grooves maximize opening force and gas film stiffness (6.2% higher stiffness vs. tree), ensuring stable non-contact operation crucial for compressor reliability at extreme pressures. Oval and fish-tail grooves offer intermediate trade-offs. Thermal analysis reveals considerable localized high temperature zones due to viscous dissipation and adiabatic compression, a key consideration for material longevity. This work establishes that groove selection fundamentally balances leakage rate (optimized by tree grooves) against hydrodynamic stability (maximized by spiral grooves). These findings provide practical guidelines for enhancing DGS performance in SCO₂ compressors, directly contributing to the viability of high-efficiency, low-emission power generation.