Unsteady Interaction Between Laminar Propagating Flame and Array of Small Fuel Droplets

实验研究了层流平面火焰在稀薄均质丙烷/空气混合气中传播时燃料液滴阵列或单个燃料液滴的点火过程。测试了由正己烷和正十六烷或正十二烷组成的二元燃料以及苯和正十六烷。还使用了由正十二烷组成的水乳化液体，以及正己烷、正辛烷、正十二烷和正十六烷等纯燃料。一个由透明管道制成的燃烧室安装了火花电极，细石英纤维悬浮燃料液滴，并在顶部安装了一个百叶窗，使燃烧的气体逸出。配备高速摄像机，对传播火焰点燃的每个液滴进行摄影观察。随着初始液滴直径的增大和燃料挥发性的减小，纯燃料液滴的点火延迟时间单调增加。初始液滴直径对点火延迟的影响随着燃油挥发性的增大而减小。随着高挥发性燃料体积浓度的增加，二元燃料液滴的点火延迟时间减小。二元燃料的点火延迟随初始液滴直径有最小和最大的变化。随着高挥发性燃料浓度的增加，点火延迟最小值和最大值处的直径减小。点火延迟或乳化燃料液滴与初始液滴直径单调一致。与二元燃料混合物相比，高挥发性组分体积浓度的增加产生了相反的结果，因为在这种情况下，高挥发性组分是水。液滴后面的部分传播火焰在通过液滴或高挥发性燃料时朝向未燃烧的气体变成凸形，而火焰在通过低挥发性燃料时保持平坦。随着高挥发性燃料浓度的增加，液滴后传播火焰的变形长度增加。少

An experimental study has been made of the ignition process of fuel droplet array or single fuel droplets subjected to a laminar flat flame propagating through a lean homogeneous propane/air mixture at constant pressure. Binary fuels consisting n-hexane and n-hexadecane or n-dodecane, and benzene and n-hexadecane were tested. Water-emulsified liquids consisting n-dodecane, and pure fuels like n-hexane, n-octane, n-dodecane and n-hexadecane were used as well. A combustion chamber made of a transparent duct was installed with spark electrodes, fine quartz fibers to suspend fuel droplets, and a shutter to allow the burned gas to escape at the top end. A high-speed video camera was provided for photographic observation of each droplet ignited by the propagating flame.Ignition delay of pure-fuel droplets increased monotonically with increase of the initial droplet diameter and decrease of fuel volatility. The influence of the initial droplet diameter on ignition delay decreased with increas … More ing fuel volatility. Ignition delay of the binary-fuel droplets decreased with increase of the volume concentration of the higher-volatility fuel. Ignition delay of the binary fuels showed a minimum and a maximum as a function of the initial droplet diameter. The diameters at the minimum and the maximum of ignition delay decreased with increasing higher-volatility fuel concentration. Ignition delay or emulsified-fuel droplets monotonically with the initial droplet diameter as expected. The increase in the volume concentration of the higher-volatility component caused an inverse result in comparison with that for the binary mixtures of fuels, since the higher-volatility component was water in this case. Part of the propagating flame behind the droplet became convex towards the unburned gas as it passed a droplet or higher-volatility fuels, while the flame remained flat for the lower-volatility fuels. The deformation length of the propagating flame behind the droplet increased with increasing higher-volatility fuel concentration. Less