Simulation study on near-field structure and flow characteristics of high-pressure CO₂ released from the pipeline

The accidental release of high-pressure carbon dioxide (CO₂) can cause serious damages to both humans and pipeline equipment. Therefore, it is of great significance to have a deeper understanding about the release characteristics of high-pressure CO₂ for improving the safety level of Carbon Capture and Storage (CCS) technologies. Both industrial-scale and laboratory-scale studies have been carried out to predict the release behaviors. In recent years, computational fluid dynamics (CFD) simulation has become a crucial method to study the instantaneous changes and microscopic details of the fluid behaviors. In this paper, the simulation method was employed to study the near-field structure and flow characteristics of high-pressure CO₂ released from pipelines. The Peng-Robinson Equation of State (EOS) was used to compute the thermodynamic properties of high-pressure CO₂, and SST k-ω model was applied to simulate the structure and physical parameters of the under-expanded jet. In addition, the multi-phase mixture model was introduced to study the phase transition. The non-equilibrium liquid/vapor transition is modeled by introducing ‘source terms’ for mass transfer and latent heat. Compared to the experimental results, the simulation results showed good agreement. Furthermore, the influences of operating conditions, including different stagnation pressure, stagnation temperature, and nozzle size, were analyzed.