为揭示液体电介质击穿过程中形成的气体放电通道对液体电介质放电过程的影响，以针—板电极间隙变压器油为研究对象，基于等离子体流体力学模型，引入了液体电介质放电过程中气相放电通道对电离机制及自由电荷迁移率的影响，建立了用于模拟脉冲电压下液体电介质放电过程的两相流体模型，仿真研究了纳秒脉冲下针板电极流注放电的起始与发展过程。仿真结果表明：采用Heaviside方程可以在模型的不同区域同时实现气相物理过程和液相物理过程的模拟与计算。气相物理过程的引入导致流注尾部电场显著降低，流注头部电场进一步增强，使流注通道的发展速度要高于传统液相模型，有助于加深对纳秒脉冲下液体电介质中预击穿流注的起始、发展过程的认识和理解。

To reveal the influence of the formation and development of gas-phase streamer channel on liquid discharge between pin-plane electrodes, a numerical model of the transformer-oil discharge in the pin-plane electrode system is built based on the continuity equations of free charge carriers, which are coupled with the Poisson’s equation. The gas-phase processes during the streamer development process is also taken into consideration, including impact ionization and the increase in the mobility of free charge carriers in the gas-phase relative to the liquid-phase in the streamer channel. The Heaviside function is used to switch the simulation model between gas-phase and liquid-phase. The initial and propagation progress of streamer discharge under nano-second pulse voltage is simulated using the model. Simulating results show that the electric field at the streamer body is significantly reduced and the electric field at the head of the streamer is further enhanced with the addition of such low density gas-phase region. The propagation speed of the streamer in two-phase model is also faster than that of the ordinary liquid-phase model.