摘要

A method to determine time-dependent volume-based drop-diameter distribution of an evaporating group of drops heterogeneous in size and distributed over an entire cross section of a water spray is proposed in this paper. Using the fact that the number of drops does not change during evaporation while their size decreases following the D² law, the time-dependent volume-based drop-diameter distribution is expressed as a function of the initial drop-diameter distribution. This time-dependent distribution is found to depend on the local initial volume-based drop-diameter distribution as well as on the initial spatial liquid volume-fraction distribution. This model allows one to determine the timedependent evaporated mass ratio, the evaporation rate and the evaporation time of the groups of drops either confined in a local region or distributed over the entire spray cross section. As an illustration, it is applied on a real spray. Measurements were performed with a laser-diffraction technique and were analyzed to report local spray characteristics, i.e., local drop-diameter distribution and local liquid concentration. The local spray characteristics are transformed into a synthetic volume-based drop-diameter distribution that describes the spray over the entire cross section and that is used as the initial condition in the evaporation model.