C4F7N混合气体电弧等离子体热力学参数计算

Calculation of Thermodynamic Properties of C4F7N Mixtures Arc Plasma

为探究新型环保绝缘气体C4F7N与不同缓冲气体的灭弧性能,理论计算了300~30000 K温度范围内、不同气压条件下(0.01、0.1、0.3、0.5和1 MPa)、不同混合比例(摩尔分数)下C4F7N/CO2、N2和空气混合气体平衡组分和热力学参数。假设电弧等离子体处于局部热力学平衡态,基于系统吉布斯自由能最小原理计算得到了粒子平衡组分;利用统计热物理的方法计算了混合气体的热力学参数;并将混合气体电弧等离子体热力学特性计算结果和SF6等气体进行了分析比较。结果表明:CO2、N2和空气的分解温度以及组成元素的差异,导致不同混合气体的热力学参数存在较大差异;相同条件下,与N2和空气相比,CO2作为缓冲气体具有更强的径向换热能力。因此,3种混合气体之中C4F7N/CO2混合气体具有更强的热开断能力。

In order to explore the arc extinguishing performance of the new environmentally friendly insulating gas C4F7N mixed with different buffer gases,we theoretically calculated the equilibrium composition and thermodynamic coefficients of C4F7N/CO2,N2 and air mixtures in the temperature range of 300~30000 K,under different pressure conditions(0.01,0.1,0.3,0.5 and 1 MPa),and in different mixing ratios(molar fraction).Assuming that the arc plasma was in the local thermodynamic equilibrium state,the equilibrium compositions were obtained based on the minimum principle of the system Gibbs free energy;the thermodynamic coefficients of the mixed gas were calculated by the statistical thermophysical method;meanwhile,the calculation results were compared with gases such as SF6.The results show that the decomposition temperature of CO2,N2 and air and the difference of constituent elements lead to large differences in thermodynamic coefficients of different mixed gases.Under the same conditions,CO2 as buffer gas has stronger radial heat exchange capacity than N2 and air.Therefore,the C4F7N/CO2 mixed gas among the three mixed gases has a stronger thermal breaking ability.