Experimental study of near-field characteristics of high-pressure CO2 pipeline leakage

•The jet structure of pipe leakage under various initial conditions and orifice diameters are obtained.•The leakage near-field parameters under various initial conditions and orifice diameters are obtained.•Experiments reveal the dominant cause of near-field characteristics of pipeline leakage.•Experiments provides input condition parameters for far-field leakage simulations. Accidental leakage poses a significant safety concern for carbon capture, utilization, and storage (CCUS) projects. Understanding the near-field characteristics of leakage is essential for dispersion studies, safety distance calculations, and risk assessment of emergency response to a pipeline leakage. This paper presents a small-scale CO2 pipeline leakage experiment designed to investigate the transient characteristics of near-field parameters, including temperature, pressure, and jet structure. The study also analyzes the effects of factors such as initial pressure, initial temperature, and leakage orifice diameter on the transient characteristics of the near-field. The experimental results demonstrate that lower initial temperatures lead to higher near-field pressure peaks, while larger orifice diameters result in larger near-field pressure peaks. Furthermore, a larger hole diameter combined with a lower initial temperature and higher initial pressure leads to the negative pressure region in the near-field being farther away from the leakage opening. In the liquid state, the near-field temperature is lower compared to the gaseous state due to the strong liquid-gas flash evaporation. When different orifice diameters are used for depressurization, larger diameters cause a more significant drop in near-field temperature. The study also reveals that the effect of initial temperature on the jet structure is less significant compared to the effect of initial pressure. The primary objective of the experiment was to collect near-field leakage data and analyze the characteristics of near-field leakage. It is hoped that this work will contribute to the improvement of research models that assess the consequences of potential high-pressure pipeline rupture scenarios.