Experiment and numerical investigation on flow characteristics and near-field structure of dense phase CO2 pipeline leakage

Accidental leakage of high-pressure CO2 is not only a safety hazard, but also may have a great negative impact on the operating efficiency of some circulating systems. To analyze the accident hazards and improve the ability to predict the transient release flow behavior of high-pressure CO2, a set of small pipeline leakage test equipment was built. The changes of near-field pressure, temperature, and jet structure under different upstream pressure (6-12 MPa), temperature (280-300 K) and orifice diameter (5 mm, 10 mm, 20 mm, 40 mm) were analyzed. Secondly, as a supplement to the experiment, the near-field CO2 gas phase distribution and critical mass flow were studied by numerical model. The results show that the near field pressure peak is negatively correlated with the initial upstream pressure, but positively correlated with the release diameter. In addition, the increase of upstream initial pressure and release diameter will lead to the increase of radial development range of near-field jet cloud. Based on the numerical results, an empirical correlation of critical mass flow based on upstream initial conditions and RHP is established. The error between the experimental data and the predicted value within the range of the correlation is within +/- 18%. The research data and results can help to enhance the understanding of the rapid release characteristics of high-pressure CO2 in the near field region and provide a basis for the study of CO2 diffusion in the far field region and the leakage risk assessment.