液态铅铋(LBE)具有较低的普朗特数(Pr)物性特征,导致计算流体力学(CFD)模拟中常用的恒定湍流普朗特数(Tr_t)模型会影响其传热计算的准确性。为提高LBE的数值传热精度,国内外的学者构建了多个液态金属Pr_t模型。为评估常用液态金属Pr_t...液态铅铋(LBE)具有较低的普朗特数(Pr)物性特征,导致计算流体力学(CFD)模拟中常用的恒定湍流普朗特数(Tr_t)模型会影响其传热计算的准确性。为提高LBE的数值传热精度,国内外的学者构建了多个液态金属Pr_t模型。为评估常用液态金属Pr_t模型在快堆常见三角形排列棒束中的适用性,本工作首先基于开源计算流体力学软件OpenFOAM的稳态传热求解器buoyantSimpleFoam,添加多个液态金属Pr_t模型。然后针对Pr分别为0.01与0.025时的常物性LBE在光滑19棒束内部的充分发展湍流换热过程进行了数值研究,并将努塞尔数(Nu)结果与Mikityuk等[Nucl Eng Des,2009,239(4):680]提出的三角形棒束换热关系式进行了对比分析。结果表明:当采用SSTk-ω湍流模型时,Aoki等[Bull Tokyo Inst Tech,1963,54:63]基于全局流动参数建立的Pr_t模型以及Kays等[ASME Journal of Heat Transfer,1994,116:284]基于局部湍流参数建立的Pr_t模型计算得到的Nu结果与Mikityuk关系式吻合较好;而Pr_t=0.85模型引起的各项误差均较大,在工程计算中应谨慎使用;LBE的分子热传导作用对温度场及热通量场的影响较大,使用合适的Pr_t模型可以改进其CFD传热计算的准确性。展开更多
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 numer...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.展开更多
文摘液态铅铋(LBE)具有较低的普朗特数(Pr)物性特征,导致计算流体力学(CFD)模拟中常用的恒定湍流普朗特数(Tr_t)模型会影响其传热计算的准确性。为提高LBE的数值传热精度,国内外的学者构建了多个液态金属Pr_t模型。为评估常用液态金属Pr_t模型在快堆常见三角形排列棒束中的适用性,本工作首先基于开源计算流体力学软件OpenFOAM的稳态传热求解器buoyantSimpleFoam,添加多个液态金属Pr_t模型。然后针对Pr分别为0.01与0.025时的常物性LBE在光滑19棒束内部的充分发展湍流换热过程进行了数值研究,并将努塞尔数(Nu)结果与Mikityuk等[Nucl Eng Des,2009,239(4):680]提出的三角形棒束换热关系式进行了对比分析。结果表明:当采用SSTk-ω湍流模型时,Aoki等[Bull Tokyo Inst Tech,1963,54:63]基于全局流动参数建立的Pr_t模型以及Kays等[ASME Journal of Heat Transfer,1994,116:284]基于局部湍流参数建立的Pr_t模型计算得到的Nu结果与Mikityuk关系式吻合较好;而Pr_t=0.85模型引起的各项误差均较大,在工程计算中应谨慎使用;LBE的分子热传导作用对温度场及热通量场的影响较大,使用合适的Pr_t模型可以改进其CFD传热计算的准确性。
文摘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.
