摘要
The main purpose of this research is the second-order modeling of flow and turbulent heat flux in nonpremixed methane-air combustion.A turbulent stream of non-premixed combustion in a stoichiometric condition,is numerically analyzed through the Reynolds averaged Navier-Stokes(RANS) equations.For modeling radiation and combustion,the discrete ordinates(DO) and eddy dissipation concept model have been applied.The Reynolds stress transport model(RSM) also was used for turbulence modeling.For THF in the energy equation,the GGDH model and high order algebraic model of HOGGDH with simple eddy diffusivity model have been applied.Comparing the numerical results of the SED model(with the turbulent Prandtl 0.85) and the second-order heat flux models with available experimental data follows that applying the second-order models significantly led to the modification of predicting temperature distribution and species mass fraction distribution in the combustion chamber.Calculation of turbulent Prandtl number in the combustion chamber shows that the assumption of Pr_(t) of 0.85 is far from reality and Pr_(t) in different areas varies from 0.4 to 1.2.
本研究的主要目的是对非预混甲烷-空气燃烧中的流动和湍流热通量进行二阶建模。采用雷诺平均Navier-stokes (RANS)方程对化学计量条件下非预混燃烧的湍流进行了数值分析。采用离散坐标和涡流耗散概念模型对辐射和燃烧进行建模,并采用RSM模型对湍流进行建模。应用GGDH模型和具有简单涡扩散模型的HOGGDH高阶代数模型对能量方程中的THF进行建模,将SED模型和二阶热通量模型的数值结果与现有的实验数据进行比较,发现应用二阶模型导致了预测燃烧室温度分布和物质质量分数分布的变化。燃烧室湍流普朗特数的计算表明,Pr为0.85与实际相差较大,不同区域的Pr从0.4到1.2不等。
