Abstract: Numerical simulation is an effective tool for studying combustion, in which the combustion model influences the results significantly. In turbulent combustion, the reaction rate not only depends on the local concentration of reactants and temperature, but also the turbulent condition. The algebraic second-order moment model (ASOM) can consider these conditions and is simpler than other models. In this study, mixing rate is considered in a modified ASOM model (RASOM). The reaction rate is calculated more accurately with RASOM in a partially stirred reactor, using the chemical time scale and the mixing time scale to demonstrate the influence of mixing rate. Simulations for a piloted methane/air diffusion flame (Sandia flame D) are carried out to verify the model. RASOM and eddy break-up model are applied in the simulations. The results are compared to experimental data of the mean axial velocity, average temperature, and mass fraction of O₂. Results from ASOM are also used in the comparison. Although the RASOM predicts the result improperly at some locations, it is more appropriate than EBU-A and ASOM. And the effect of mixing rate on the reaction rate in RASOM is discussed in detail.

Key words: turbulent flow, non-premixed combustion, numerical simulation, mixing rate, model

摘要： 湍流燃烧数值模拟是研究燃烧的一种重要手段，采用的湍流燃烧模型是否恰当直接影响最终结果的准确性。在湍流燃烧中，化学反应速率不仅取决于当地的组分浓度和温度，而且与组分的湍流脉动也有密切关系。通过对湍流燃烧模型进行探讨，发现代数二阶矩模型（ASOM）能综合考虑湍流和反应动力学因素的影响，而且比其他复杂的模型简单。研究将组分混合速率对化学反应速率的影响在一个修正的代数二阶矩模型（RASOM）中进行考虑，更准确地计算出化学反应速率。为了验证模型的准确性，RASOM模型被应用到Sandia实验室测量的甲烷-空气非预混燃烧（Flame-D）的数值模拟中。模拟得到的结果与实验结果以及修正的涡破碎模型（EBU-A）和原ASOM模型的结果进行了对比，发现RASOM模型的效果较好。

关键词: 湍流, 非预混燃烧, 数值模拟, 混合速率, 模型