标题： 燃料配比对狭窄通道中预混火焰传播的影响：对称破缺分岔 显示英文标题

标题： Effects of stoichiometry on premixed flames propagating in narrow channels: symmetry-breaking bifurcations

摘要： 最近在扩散-热（恒定密度）近似下的研究显示，对于在狭窄绝热通道中自由传播的预混火焰，由差分扩散引起的不稳定性可能导致非对称解和/或振荡和旋转传播模式。 这一点已在贫燃混合物的背景下得到证明，对于这种混合物，可以使用一个具有单一莱利数（对应于不足反应物的热扩散率与分子扩散率的比值）的物种传输方程来描述火焰传播问题。 在本工作中，我们将分析扩展到任何当量比的混合物。为此，我们考虑了一个双反应物模型，其中两个反应物的不同扩散率引入了两个不同的莱利数。 对燃料（LeF）和氧化剂（LeO）的莱利数之间存在显著差异的混合物进行了稳态计算和线性稳定性分析，例如氢氧系统。 结果表明，差分扩散和优先扩散都会影响对称火焰形状的稳定性。 对于足够贫和富的混合物，火焰的行为由不足反应物的莱利数决定，即当所述莱利数小于一时，在大质量流量下火焰会向非对称解不稳定化。 在接近化学计量的混合物中，对称火焰的稳定性取决于LeF和LeO的加权平均值。 特别是，由于较难扩散的反应物难以到达火焰的反应区，因此在大质量流量下对称解是稳定的。 显示英文摘要

摘要： Recent studies within the diffusive-thermal (constant-density) approximation have shown that, for premixed flames freely propagating in narrow adiabatic channels, the instabilities induced by differential diffusion may result in non-symmetric solutions and/or oscillating and rotating propagation modes. This has been shown in the context of lean mixtures, for which a single species transport equation with a single Lewis number (corresponding to the ratio of thermal to molecular diffusivity of the deficient reactant) can be used to describe the flame propagation problem. In the present work we extend the analysis to mixtures of any equivalence ratio. To this end, we consider a two-reactant model, where the different diffusivities of the two reactants introduce two different Lewis numbers. Steady-state computations and linear stability analysis are carried out for mixtures with large disparity between the Lewis number of the fuel (LeF) and the oxidizer (LeO), such as hydrogen-oxygen systems. It is shown that both differential diffusion and preferential diffusion have influence on the stability of the symmetric flame shape. For sufficiently lean and rich mixtures, the flame behaves as dictated by the Lewis number of the deficient reactant, i.e., the flame destabilizes toward non-symmetric solutions for large mass flow rates when the mentioned Lewis number is less than one. In near-stoichiometric mixtures the stability of the symmetric flame depends on a weighted average value of LeF and LeO. In particular, the symmetric solution is stable for large mass flow rates because of the difficulties found by the less diffusive reactant to reach the reactive zone of the flame.