对流速度对燃料液滴火焰形态及燃烧的影响

考虑气相非稳态及液滴内部环流,建立运动液滴非稳态蒸发燃烧模型.模型采用动网格方法精确追踪液滴表面位置,采用守恒方程组更新液滴表面边界条件.根据单步全局化学反应机理,仿真研究正庚烷燃料液滴在不同对流速度下的火焰形态及燃烧.结果表明:运动液滴内部环流使液滴内部低温区向环流中心移动.当液滴运动速度大于某临界值后,火焰形态由包覆火焰转变为尾迹火焰.包覆火焰的富燃区范围、高温区范围及燃烧速率明显较尾迹火焰大;包覆火焰的液滴表面温度及表面蒸发流率分布也明显不同于尾迹火焰.

Convective Velocity Effect on Flame Shape and Combustion of Fuel Droplets

Considering gas phase unsteadiness and droplet internal recirculation,we developed an unsteady evaporation and combustion model for moving droplets.It adopts dynamic grid method tracking droplet interface location and conservation equations updating interface boundary conditions.Based on one step global chemical reaction,flame shape and combustion characteristics of n-heptance droplets at different convective velocity are simulated and analyzed.It shows that internal recirculation of moving droplet promotes low temperature area moving to the center of recirculation.Envelop flame translates into wake flame as convective velocity exceeding a critical value.Area of fuel rich and high temperature region and combustion rate at envelop flame are higher than those of wake flames remarkably.Droplet surface temperature and evaporation rate distribution at an envelop flame are different from those of wake flame obviously as well.