Droplet combustion has been studied by experiments and numerical simulation for many years, and most of studies were done about single droplets. As for droplet groups, some theoretical and experimental studies were reported, but less of numerical studies. One of the important characteristics is the drag of combusting droplets, which is closely related to flame structure and is a sub-model in numerical simulation of spray combustion. There are contradictory research results for the drag of combusting droplets. In the present paper, large-eddy simulation (LES) is used to study the flame structure and drag of a combusting ethanol-droplet group. The results show that there are three combustion modes: fully-enveloped flame, partially-enveloped flame and wake flame in a droplet group, leading to the change of the drag with inlet velocities. It is found that the drag of droplets in the group is much smaller than that of a non-combusting particle in isothermal flows
This study was sponsored by the Key Project of National Natural Science Foundation of China under the Grant 51390493
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