压力比对高压SF_6断路器喷口中冷态气流场影响的研究

Influence of Pressure Ratios on Cold Gas Flow Field in HV SF_6 Circuit Breaker Nozzles

为了辅助高压SF6断路器灭弧室的设计和优化,以拉法尔喷口结构为基础,对3种长度喷口结构下的冷态SF6气流场进行了数值计算和分析.通过对比压力与马赫数的变化特点,研究了上、下游压力以及喷口长短对气流场分布的影响.确定了3种长度喷口对应的临界压力比值,并着重分析了压力比与激波产生和运动之间的关系,讨论了物性参数所引起的计算误差.结果表明:不同长度的喷口结构,临界压力比不同,当上下游压力比低于临界值时,喷口中产生激波,反之则无激波产生;激波的位置随着压力比以及喷口的长度而变化;当喷口下游气体始终处于超音速流动时,出口压力与设定值无关,仅随着入口压力的增加而增大.此外,有效地导入气体属性能够降低数值仿真中的误差,提高仿真结果的精度.

Cold SFG gas flow field is calculated and analyzed for three kinds of Laval nozzle structures to guide thermal gas flow field simulation in high voltage circuit breakers. The influences of different nozzle length, upstream and downstream pressures are investigated by comparing the variety characteristics of the pressure and the Mach number. The critical pressure values of the three nozzle structures are confirmed. The relationship between shock initiation and pressure ratio is analyzed, and the calculation error caused by available plasma properties data is discussed. The results show that different length nozzle structures are with different critical pressure values. The shocks appear when the pressure ratio is lower than the critical value, otherwise no shock arising. Shock position varies with the pressure ratio and nozzle length. The outlet pressure is independent on the setting value and increases with the inlet pressure when the gas flow velocity gets always supersonic along in the nozzle downstream. The error in the simulation can be reduced with the effective implementation of the gas properties, which may improve the accuracy of the calculation results.