Evolution of fuel droplet evaporation zone and its interaction with propagating flame front are studied in this work. A general theory is developed to describe the evolutions of flame propagation speed, flame temperature, droplet evaporation onset and completion locations in ignition and propagation of spherical flames. The influences of liquid droplet mass loading, heat exchange coefficient (or evaporation rate) and Lewis number on spherical spray flame ignition are studied. Two flame regimes are considered, that is, heterogeneous and homogeneous flames, based on the mixture condition near the flame front. The results indicate that the spray flame trajectories are considerably affected by the ignition energy addition. The critical condition for successful ignition for the fuel-rich mixture is a coincidence of inner and outer flame balls from igniting kernel and propagating flame. The flame balls always exist in homogeneous mixtures, indicating that ignition failure and critical successful events occur only in purely gaseous mixture. The fuel droplets have limited effects on minimum ignition energy, which, however, increases monotonically with the Lewis number. Moreover, flame kernel originates from heterogeneous mixtures due to the initially dispersed droplets near the spark. The evaporative heat loss in the burned and unburned zones of homogeneous and heterogeneous spray flames is also evaluated, and the results show that for the failed flame kernels, evaporative heat loss behind and before the flame front first increases and then decreases. The evaporative heat loss before the flame front generally increases, although non-monotonicity exists, when the flame is successfully ignited and propagate outwardly. For heterogeneous flames, the ratio of the heat loss from the burned zone to the total one decreases as the flame expands. Moreover, droplet mass loading and heat exchange coefficient considerably affect the evaporating heat loss from burned and unburned zones.

这项工作研究了燃料液滴蒸发区的演变及其与传播火焰前锋的相互作用。开发了一个通用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在球形火焰的点火和传播中的演变。研究了液滴质量负载、热交换系数（或蒸发速率）和路易斯数对球形喷雾火焰点火的影响。基于火焰前沿附近的混合条件，考虑了两种火焰状态，即异质火焰和均质火焰。结果表明，喷射火焰轨迹受点火能量增加的影响很大。成功点燃富含燃料的混合物的临界条件是来自点燃内核和传播火焰的内外火焰球的重合。火焰球始终存在于均质混合物中，表明点火失败和临界成功事件仅发生在纯气态混合物中。燃料液滴对最小点火能量的影响有限，然而，它随路易斯数单调增加。此外，由于最初分散在火花附近的液滴，火焰核起源于异质混合物。还对均质和非均质喷射火焰的燃烧区和未燃烧区的蒸发热损失进行了评估，结果表明，对于失效的火焰核，火焰前锋前后的蒸发热损失先增加后减少。当火焰成功点燃并向外传播时，尽管存在非单调性，但火焰前锋前的蒸发热损失普遍增加。对于异质火焰，燃烧区的热损失与总热损失的比率随着火焰的膨胀而减小。此外，液滴质量负载和热交换系数显着影响燃烧区和未燃烧区的蒸发热损失。