Application of the D2-Law to Determine Time Evolution and Burn-Out Time of Evaporating Biodiesel Spray Drop-Size Distribution

Abstract

This paper applies the D²-law to a group of heterogeneous size of biodiesel drops in order to determine the time evolution of the drop-size distribution and its burn-out time. Experiments to determine initial drop distribution data, used for predicting the evaporation time, have been performed on a biodiesel spray issuing from a small scale industrial burner. The measured drop-size distribution has been first transformed into a dimensionless form, called mass-based drop-diameter distribution, before its time dependent distribution and the evaporation time are calculated. It is found that the D²-law, originally applied for determining the evaporation time of a droplet, can be adapted well to calculate the time evolution of the drop-size distribution and its evaporation time. The dimensionless evaporation time is shortest for a group of mono-sized drops and prolonged for a drop-size distribution provided that they are at the same initial mean diameter. Furthermore, if the initial dimensionless mass distributions contain high proportion of small drops; it is prone to evaporate faster than those containing larger drops. The dimensionless evaporation times obtained from this study are the analysis results of the drop-size distribution along the line-of-sight measurement data. In this work, the variations of the volume concentration along the line-of-sight are omitted.