Experimental study of a multi-bag breakup regime at transition stage in a continuous and uniform air jet flow

摘要

The properties of a multi-bag breakup regime at the transition stage were investigated at normal temperature and pressure. Measurement was carried out in a continuous and uniform air jet flow using shadowgraph and high-speed camera to observe the process and mechanism of breakup of bags. Various concentrations of glycerol solutions were tested with Weber number in the region of 30-120, Ohnesorge numbers less than 0.1, liquid/gas density ratios greater than 500. From experimental observations, the evolution properties of the multi-bag breakup regime with increasing Weber number is characterized by three successive bag breakup processes. The first one is a primary bag breakup, the second one is multiple bags suffered by the initial main drop, and the third one is suffered by the core drop produced in the above breakup processes. It is observed that the core drops became smaller associated with the increase of Weber number, until progressively evolve into a parent drop and ligament system as the shear breakup regime is approached at a Weber number of roughly 105. Parameters including breakup time, drop deformation properties, the frequency of bag occurrences were researched. The results show that multiple bags have a great effect on size of core drops, they share in much mass percent of whole drop so that there is not enough components to produce a bag breakup of the core drops. It's expected that the transition stage could be explained with multi-bag breakup regime, which is important to interpret the breakup mechanism in complex conditions of higher Weber numbers.