喷射压力变化对脉冲等离子射流扩展特性的影响

Influence of Injection Pressure Change on Expansion Characteristics of Pulsed Plasma Jet

为分析喷射压力变化对脉冲等离子射流扩展特性的影响，建立脉冲等离子射流在空气中扩展的二维轴对称非稳态模型，并进行数值模拟。研究了1．5～3．5MPa喷射压力范围内，脉冲等离子射流在空气中扩展时的两相界面演化特性及流场参数变化规律，并与实验结果进行对比。研究结果表明：脉冲等离子射流的轴向扩展位移模拟值与实验值较为吻合；喷嘴出口处，射流场参数骤变，近场处参数变化较为剧烈，后期逐渐衰减至环境参数；喷射压力增大时，脉冲等离子射流的扩展体积、马赫盘大小及压力等流场参数均随之增大，扩展过程中的湍流掺混现象也随之增强，表现为等离子体与空气两相界面破碎加剧；喷射压力减小到1MPa时，喷嘴近场无马赫盘出现。

To analyze the influence of injection pressure on the expansion characteristics of pulsed plasma jet, a two-dimensional axisymmetric unsteady model for pulsed plasma jet expansion in air is established, and the numerical simulation of this process is carried out. The evolution characteristics of two-phase interface and the variation of flow field parameters of pulsed plasma jet in air are studied in the range of 1.5 - 3.5 MPa jet pressure, then compared with the experiments. Results show that the simulation values of axial expansion displacement of pulsed plasma jet are in good agreement with the experimental results. The parameters of the jet field are mutated at the nozzle exit, the pulse decays near the nozzle, and then it gradually decays to environmental parameters. When the injection pressure increases, the parameters of flow field, such as the expansion volume of pulsed plasma jet, the size of Mach disk and the pressure, increase, and the turbulent mixing in the expansion process is also enhanced, which is characterized by the more fracture of the interface of the plasma and air. When the injection pressure reduces to 1 MPa, no Maher disk appears at nozzle.