The frequent occurrence of Liquefied natural gas (LNG) leakage accidents has caused serious economic loss and environmental damage. Therefore, it's of great significance to make assessments on the LNG hazards during its accidental release and associated consequences. This paper focuses on the two-phase release process in the liquefied gas release and dispersion accident and makes investigatatation on the two-phase plume with experimental and numerical approaches. A small-scale experimental system is developed with different sizes of release holes. With the experiment results, the mass outflow rate and temperature have been obtained, which provided initial parameters for the simulation. Jet velocities have been measured by PIV, and results reveal that an obvious velocity breach existing near the leakage nozzle due to the Joule-Thomson effect. Besides, given a point in the X-axis, the jet velocity is decreasing with an increasing diameter hole. Subsequently, the experimental data are utilized to verify the liquid-gas phase numerical model using Eulerian-Lagrange approach. Comparing with the results obtained by single gas phase model, the velocities obtained by liquid-gas phase model show good consistency with the experiments. Afterwards, the validated numerical liquid-gas phase model is employed to analyze the temperature distribution, concentration distribution and droplet size distribution in the near-source release region. With the simulation results, it depicts that there is a violent temperature decrease near the leakage nozzle in the liquid-gas phase model, which was caused by the evaporation of droplets. Meanwhile, concentration of R134a simulated by liquid-gas phase model is higher than the value of single-gas phase. These results emphasize that it’s essential to simulate the release accidents with liquid-gas phase model, especially in the near-source region. Both the experiments and numerical models are of great value for providing assessments and theoretical supports for the risk consequences in the process safety.

液化天然气（LNG）泄漏事故频发，造成了严重的经济损失和环境破坏。因此，对LNG意外泄漏过程中的危害及相关后果进行评估具有重要意义。本文针对液化气泄放扩散事故中的两相泄放过程，采用实验和数值方法对两相烟羽进行了研究。开发了具有不同尺寸释放孔的小型实验系统。根据实验结果，得到了质量流出速率和温度，为模拟提供了初始参数。PIV 测量了射流速度，结果表明，由于焦耳-汤姆逊效应，泄漏喷嘴附近存在明显的速度缺口。此外，给定 X 轴上的一个点，射流速度随着孔直径的增加而降低。随后，利用实验数据来验证使用欧拉-拉格朗日方法的液-气相数值模型。与单一气相模型获得的结果相比，液-气相模型获得的速度与实验具有良好的一致性。随后，利用经过验证的液-气相数值模型对近源释放区的温度分布、浓度分布和液滴粒径分布进行分析。模拟结果表明，液-气相模型中泄漏喷嘴附近温度急剧下降，这是由液滴蒸发引起的。同时，液-气相模型模拟的R134a浓度高于单气相值。这些结果强调了利用液-气相模型模拟泄漏事故的必要性，尤其是在近源区。实验和数值模型对于为过程安全中的风险后果提供评估和理论支持具有重要价值。