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.

高压二氧化碳（CO ₂）的意外释放可能对人员和管道设备造成严重损害。因此，深入了解高压CO ₂的释放特性对于提高碳捕集与封存（CCS）技术的安全水平具有重要意义。已经进行了工业规模和实验室规模的研究以预测释放行为。近年来，计算流体动力学（CFD）模拟已成为研究流体行为的瞬时变化和微观细节的关键方法。本文采用模拟方法研究了高压CO ₂的近场结构和流动特性。从管道释放。用Peng-Robinson状态方程（EOS）计算高压CO ₂的热力学性质，并使用SSTk-ω模型模拟膨胀不足射流的结构和物理参数。此外，引入了多相混合模型以研究相变。通过引入传质和潜热的“源项”来模拟非平衡的液体/蒸气转化。与实验结果相比，仿真结果吻合良好。此外，分析了工作条件的影响，包括不同的停滞压力，停滞温度和喷嘴尺寸。