无缓冲气COIL扩压器流场数值模拟

 以无缓冲气化学氧碘激光器(COIL)实验器件的数据计算得到的混合喷管出口参数平均值作为光腔入口条件，对6种不同构型的扩压器从光腔入口至扩压器出口的流场进行了数值模拟，得出了各流场参数分布；对不同构型扩压器的流场特点、总压恢复性能进行了分析；研究了扩压器出口背压对流场参数的影响。结果表明：对于主流无缓冲气的COIL，等截面扩压器具有较好的压力恢复性能；增大扩压器出口背压可以使扩压器的压力恢复性能提高，然而，较高的背压使激波串向光腔方向移动，从而使光腔流场受到干扰，影响光腔的光束质量。

Flow field numerical simulation for the diffuser of COIL without primary buffer gas

Using the average parameters at the outlet of a mixing nozzle calculated based on experimental data of a chemical oxygen-iodine laser(COIL) apparatus without primary buffer gas as input conditions,the flow fields from the inlet of optical cavity to the outlet of diffuser for six different diffuser configurations were numerically simulated.Contours of different flow field parameters such as Mach number,static pressure,and total pressure etc.were obtained.The flow field characteristics and the total pressure recovery performance for different diffuser configurations were analyzed.The effect of back pressure at the diffuser outlet on flow field parameters was also studied.The results indicate that the diffuser with constant cross section has better pressure recovery performance for COIL without primary buffer gas;and the pressure recovery performance of a diffuser can be improved by means of increasing the diffuser back pressure.However,the shock train region may move towards the optical cavity under higher back pressure,as a result,the flow field inside the optical cavity may be disturbed and the laser beam quality may be affected.