Experimental investigation of the passage of fuel droplets through a spherical two-phase flame
Résumé
This paper reports experimental studies of two-phase combustion carried out with an aerosol of monosized ethanol droplets generated by rapid expansion under microgravity conditions. Optical diagnostics consisting of coupling laser tomography with the high-speed ILIDS technique are successfully applied for the aerosol combustion study. Droplet diameter reduction together with the radial droplet displacement ahead of the flame front is accurately measured. It is found that fuel droplets evaporate by following the d 2 law which confirms the validity of this model in an aerosol configuration. The laser tomography technique allows the identification of droplets which are present in the burnt gases. A regime diagram has been built using relevant non-dimensional parameters of two-phase combustion to exhibit the observations of droplets crossing. The results demonstrate that the droplet size and the droplet interdistance are the most important parameters which control the possibility for the droplet to penetrate the burnt gases. Moreover, it is observed that typical topologies of flames in terms of size and number of cells are related to the droplet number density.