Diffusive transport of mass occurs at small scales in turbulent premixed flames. As a result, multicomponent mass diffusion, which is often neglected in direct numerical simulations (DNS) of premixed combustion, has the potential to impact both turbulence and flame characteristics at small scales. In this study, we evaluate these impacts by examining enstrophy dynamics and the internal structure of the flame for lean premixed hydrogen-air combustion, neglecting secondary Soret and Dufour effects. We performed three-dimensional DNS of these flames by implementing the Stefan–Maxwell equations in the code NGA to represent multicomponent mass transport, and we simulated statistically planar lean premixed hydrogen-air flames using both mixture-averaged and multicomponent models. The mixture-averaged model underpredicts the peak enstrophy in the multicomponent simulation by up to 13% in the flame front. Comparing the enstrophy budgets of these flames, the multicomponent simulation yields larger peak magnitudes compared to the mixture-averaged simulation in the reaction zone, showing differences of 17% and 14% in the normalised vortex stretching and viscous effects terms. In the super-adiabatic regions of the flame, the mixture-averaged model overpredicts the viscous effects by up to 13%. To assess the effect of these differences on flame structure, we reconstructed the average local internal structure of the turbulent flame through statistical analysis of the scalar gradient field. Based on this analysis, we show that large differences in viscous effects contribute to significant differences in the average local flame structure between the two models.

在湍流预混火焰中，质量的扩散传输发生在小范围内。因此，在预混燃烧的直接数值模拟 (DNS) 中经常被忽略的多组分质量扩散有可能在小尺度上影响湍流和火焰特性。在这项研究中，我们通过检查熵动力学和稀薄预混氢空气燃烧的火焰内部结构来评估这些影响，忽略二次 Soret 和 Dufour 效应。我们通过在代码 NGA 中实施 Stefan-Maxwell 方程来表示多组分质量传递，对这些火焰进行了三维 DNS，并且我们使用混合平均模型和多组分模型在统计上模拟了平面贫氢预混氢-空气火焰。混合平均模型将多组分模拟中的峰值熵低估了高达 13% 的火焰前沿。比较这些火焰的熵预算，与反应区中的混合物平均模拟相比，多组分模拟产生更大的峰值幅度，在归一化涡旋拉伸和粘性效应项中显示出 17% 和 14% 的差异。在火焰的超绝热区域，混合平均模型高估了高达 13% 的粘性效应。为了评估这些差异对火焰结构的影响，我们通过标量梯度场的统计分析重建了湍流火焰的平均局部内部结构。基于这一分析，