氧气/煤油发动机燃气热物理参数及输运系数计算

摘要

为了给氧气/煤油发动机设计和热防护设计提供必要的设计参数,针对氧气/煤油燃气进行热力学计算.运用吉布斯最小自由焓计算模型得到燃气平衡组成,通过拟合公式的方法得到燃气的热物理参数及输运系数.通过计算,得到氧气/煤油燃气的组分及比焓、 密度、比熵、 粘性系数等热物理参数和输运系数随温度和压力的变化特性.分析结果表明:水离解对氧气/煤油燃气组分变化存在显著影响,压力增大会导致水离解起始温度升高;氧气/煤油燃气比焓、 比熵、 定压比热、 粘性系数、 热传导系数变化在温度较低时受压力影响较小,当水开始离解后,压力的影响显著增强;组分在燃气中的扩散系数同时受到了温度和组分摩尔分数的影响;燃气普朗特数变化受热传导系数变化的影响较大,水离解后,热传导系数的迅速增大使燃气的普朗特数迅速减小.%In order to provide necessary design parameters for design of the oxygen/kerosene engine and thermal protection, thermodynamic calculation of oxygen/kerosene gas is studied in this paper. The minimization Gibbs free energy calculation model was used to determine equilibrium compositions. The thermodynamic parameters and transport coefficients were derived with a fitting method of formulas. The variation characteristics of equilibrium compositions, and thermodynamic parameters and transport coefficients of oxygen/kerosene gas with pressure and temperature were obtained. The analysis results indicate that hydrolytic dissociation has an significant impact on the equilibrium compositions, and the pressure increase may cause the rising of the initial temperature of hydrolytic dissociation; the pressure began to affect thermodynamic and transport properties seriously after hydrolytic dissociation at high temperature; the diffusion coefficient of components in fuel gas are influenced by the combined effect of temperature and mole fractions. Thermal conductivity has a great effect on Prandtl number. After H2O is dissociated,Prandtl number reduces fast as the thermal conductivity increases quickly.