论文标题
局部均质和异质反应物中弱拉伸预混合的球形喷雾的传播
Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants
论文作者
论文摘要
从理论上研究了这项工作，在部分预先蒸发的燃料喷雾剂中繁殖弱拉伸的球形火焰的传播。开发了一种一般理论来描述火焰传播速度，火焰温度，液滴蒸发开始和完成位置。研究了液体燃料和气体混合物特性对球形喷雾繁殖的影响。结果表明，随着液滴质量负载和/或蒸发热量系数（或蒸发率），喷雾火焰传播速度得到了提高。由于强烈的蒸发热吸收，当潜热较高时，发现相反的趋势。在异质火焰的火焰后蒸发区观察到燃料蒸气和温度梯度。蒸发完成前部位置随火焰半径发生了很大变化，但是当火焰繁殖时，蒸发发作位置相对于火焰前部几乎没有变化。对于较大的液滴载荷和较小的蒸发速率，燃油液滴倾向于在火焰前后完全蒸发。火焰分叉发生在大液滴质量载荷下，在大型潜热下，导致火焰繁殖速度多样，液滴蒸发开始和完成前线。燃油液滴喷雾剂的火焰增强或弱化的影响通过燃料前区域的热量或抑制质量扩散过程揭示出来。此外，对于异质的火焰，也存在火焰后区域中的热量和质量扩散。随着路易斯数量减少，均质和异质火焰的质量扩散得到了增强。随着液滴载荷的增加，马克斯坦长度的大小大大降低。此外，当液体燃料负载相对较低时，在异质火焰后面燃烧的火焰后液滴会影响火焰传播速度和Markstein长度。
Propagation of weakly stretched spherical flames in partially pre-vaporized fuel sprays is theoretically investigated in this work. A general theory is developed to describe flame propagation speed, flame temperature, droplet evaporation onset and completion locations. The influences of liquid fuel and gas mixture properties on spherical spray flame propagation are studied. The results indicate that the spray flame propagation speed is enhanced with increased droplet mass loading and/or evaporation heat exchange coefficient (or evaporation rate). Opposite trends are found when the latent heat is high, due to strong evaporation heat absorption. Fuel vapor and temperature gradients are observed in the post-flame evaporation zone of heterogeneous flames. Evaporation completion front location considerably changes with flame radius, but the evaporation onset location varies little relative to the flame front when the flame propagates. For larger droplet loading and smaller evaporation rate, the fuel droplet tends to complete evaporation behind the flame front. Flame bifurcation occurs with high droplet mass loading under large latent heat, leading to multiplicity of flame propagation speed, droplet evaporation onset and completion fronts. The flame enhancement or weakening effects by the fuel droplet sprays are revealed by enhanced or suppressed heat and mass diffusion process in the pre-flame zone. Besides, for heterogeneous flames, heat and mass diffusion in the post-flame zone also exists. The mass diffusion for both homogeneous and heterogeneous flames is enhanced with decreased Lewis number. The magnitude of Markstein length is considerably reduced with increased droplet loading. Moreover, post-flame droplet burning behind heterogeneous flame influences the flame propagation speed and Markstein length when the liquid fuel loading is relatively low.
