Abstract Experimental and computational studies are carried out to elucidate the structure and extinction of laminar partially-premixed flames employing the counterflow configuration. The fuel is methoxymethane (DME). The formulation considers two laminar streams that flow toward a stagnation plane. One stream called the fuel-rich stream is made up of DME (CH3OCH3), and nitrogen (N2) with small amounts of oxygen (O2) and the other stream called the fuel-lean stream is made up of O2, and N2 with small amounts of CH3OCH3. The level of partial premixing is characterized by the equivalence ratio defined as the ratio of the mass of methoxymethane to the mass of oxygen normalized by the corresponding stoichiometric value of this ratio. The equivalence ratio of the fuel-rich stream is ϕr and that of the fuel-lean stream is ϕl. Previous studies have established that the scalar dissipation rate at extinction depends on the stoichiometric mixture fraction, ξst, and the adiabatic flame temperature, Tst. To clarify the chemical influences of partial premixing on extinction, studies are carried at fixed values of ξst and Tst and for various values of ϕl and ϕr. Use of this procedure separates the chemical influences from thermal effects. A previously developed Burke–Schumann (flame-sheet) formulation is employed to estimate the boundary values of the mass fractions of the reactants. Two sets of experiments are conducted, in one set ϕ r − 1 = 0 , and measurements are made for various selected values of ϕl, in the other set ϕ l = 0 and measurements are made for various selected values of ϕr. The computations are carried out using the San Diego mechanism that was recently updated to include kinetic steps describing combustion of methoxymethane. For DME addition to the fuel-lean stream, experiments and predictions show that the value of the strain rate at extinction, increases with increasing ϕl. For O2 addition to the fuel-rich stream, experiments and predictions show very little changes in the values of the strain rate at extinction with increasing ϕ r − 1 . The key observation is that addition of DME to the fuel-lean stream enhances the overall reactivity while addition of oxygen to the fuel-rich stream has little influence on the overall reactivity

中文翻译：

---

部分预混甲氧基甲烷火焰的实验和计算研究

摘要 进行了实验和计算研究，以阐明采用逆流配置的层流部分预混火焰的结构和熄灭。燃料是甲氧基甲烷 (DME)。该公式考虑了流向停滞平面的两个层流。一种称为富燃料流的流由 DME (CH3OCH3)、氮气 (N2) 和少量氧气 (O2) 组成，另一种称为贫燃料流的流由 O2 组成，N2 与少量氧气 (O2) 组成。 CH3OCH3 的量。部分预混水平的特征在于当量比，定义为甲氧基甲烷的质量与氧气质量的比值，通过该比值的相应化学计量值归一化。富燃料流的当量比为 ϕr，贫燃料流的当量比为 ϕl。先前的研究已经确定，消光时的标量耗散率取决于化学计量混合分数 ξst 和绝热火焰温度 Tst。为了阐明部分预混对消光的化学影响，对 ξst 和 Tst 的固定值以及 ϕl 和 ϕr 的各种值进行了研究。使用此程序将化学影响与热效应分开。采用先前开发的 Burke-Schumann（火焰板）公式来估计反应物质量分数的边界值。进行了两组实验，在一组 ϕ r − 1 = 0 中，对各种选定的 ϕl 值进行测量，在另一组 ϕ l = 0 中，对各种选定的 ϕr 值进行测量。计算是使用圣地亚哥机制进行的，该机制最近更新为包括描述甲氧基甲烷燃烧的动力学步骤。对于将 DME 添加到贫燃料流中，实验和预测表明消光应变率的值随着 ϕl 的增加而增加。对于向富燃料流中添加 O2 的情况，实验和预测表明，随着 ϕ r − 1 的增加，消光应变率值几乎没有变化。关键观察结果是，向贫燃料流中添加 DME 可增强整体反应性，而向富燃料流中添加氧气对整体反应性几乎没有影响 实验和预测表明，消光应变率的值随着 ϕl 的增加而增加。对于向富燃料流中添加 O2 的情况，实验和预测表明，随着 ϕ r − 1 的增加，消光应变率值几乎没有变化。关键观察结果是，向贫燃料流中添加 DME 可增强整体反应性，而向富燃料流中添加氧气对整体反应性几乎没有影响 实验和预测表明，消光应变率的值随着 ϕl 的增加而增加。对于向富燃料流中添加 O2 的情况，实验和预测表明，随着 ϕ r − 1 的增加，消光应变率值几乎没有变化。关键观察结果是，向贫燃料流中添加 DME 可增强整体反应性，而向富燃料流中添加氧气对整体反应性几乎没有影响