发表机构
University of Pisa; The University of Edinburgh（比萨大学; 爱丁堡大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过直接数值模拟发现，燃料分层长度尺度通过几何机制调控热扩散不稳定贫燃氢火焰的结构与传播速度，为部分预混氢燃烧器设计提供关键依据。
AI 中文摘要
贫燃预混氢火焰极易发生热扩散不稳定，这种不稳定会产生胞状结构并增强火焰传播速度。在实际燃烧器中，不完全预混会在火焰上游引入局部当量比的空间变化。本研究通过使用详细化学机理和输运过程的直接数值模拟，探讨了入口燃料分层的特征长度尺度如何影响贫燃层流氢火焰的结构和传播。在保持密度加权全局当量比恒定的条件下，施加受控的正弦扰动于燃料质量分数，并使用被动示踪剂独立于燃烧化学和微分扩散来追踪所施加的分层。结果表明存在强烈的尺度依赖性响应。当分层波长与大型热扩散结构的间距相当（λ ≈ 20 δ_f）时，横向组分梯度会破坏热扩散指状结构，相对于完全预混参考情形，火焰表面积和传播速度均有所降低。对于较大波长（λ ≳ 40 δ_f），分层将火焰组织成交替的富燃和贫燃通道，热扩散胞优先在富燃区域发展，而尖角状结构在贫燃区域形成。这增加了火焰表面积和整体传播速度。拉伸因子在所有情况下几乎保持不变，表明主导机制是几何性的：即大型火焰结构的尺度依赖性生成或抑制，而非局部燃烧行为的显著变化。这些发现凸显了分层长度尺度在控制热扩散不稳定氢火焰中的关键作用，对部分预混氢燃烧器的建模和设计具有启示意义。
英文摘要
Lean premixed hydrogen flames are highly susceptible to thermodiffusive instabilities, which generate complex cellular structures and enhance propagation speed. In practical combustors, incomplete premixing introduces spatial variations in local equivalence ratio upstream of the flame. This work investigates how the length scale of inlet fuel stratification affects the structure and propagation of lean laminar hydrogen flames using direct numerical simulations with detailed chemistry and transport. Controlled sinusoidal perturbations of fuel mass fraction are imposed at moderate amplitude, leading to local equivalence-ratio variations of $ϕ\simeq 0.45-0.55$ in the flame region. Seven stratification wavelengths, from $λ= 15.4δ_f$ to $133.3δ_f$, are examined at constant density-weighted global equivalence ratio. Additional unity-Lewis-number simulations separate geometrical effects from differential transport. The results reveal a strongly scale-dependent response. In unity-Lewis-number flames, stratification organises the front at the imposed wavelength and monotonically increases flame surface area and propagation speed with wavelength. With differential diffusion, large wavelengths ($λ\gtrsim 40δ_f$) produce a similar large-scale organisation, with rich channels forming forward bulges and lean channels recessed cusps, while thermodiffusive cells remain superimposed. This increases flame surface area and global propagation speed. At smaller wavelengths ($λ\lesssim 29δ_f$), composition gradients interfere with intrinsic thermodiffusive cellular dynamics, reducing flame surface area and propagation speed relative to the perfectly premixed reference. These findings identify stratification length scale as a key parameter controlling the interaction between moderate mixture inhomogeneity and thermodiffusive instability in lean hydrogen flames.
Journal refProceedings of the Combustion Institute 42 (2026) 106466
DOI：10.1016/j.proci.2026.106466
