TWO-PHASE JET RELEASES AND DROPLET DISPERSION: SCALED AND LARGE-SCALE EXPERIMENTS, DROPLET-SIZE CORRELATION DEVELOPMENT AND MODEL VALIDATION

摘要

Many accidents involve two-phase releases ofhazardous chemicals into the atmosphere. This paperdescribes the results of a third phase of a Joint IndustryProject (JIP) on liquid jets and two-phase dropletdispersion. The aim of the project is to increase theunderstanding of the behaviour of sub-cooled nonflashingand superheated flashing liquid jets, and toimprove the prediction of droplet atomisation, dropletdispersion and rainout.Phase III of the JIP first included scaled experiments formaterials with a range of volatilities (water,cyclohexane, butane, propane and gasoline). Theseexperiments were carried out by Cardiff Universityincluding measurements of flow rate and initial dropletsize across the full relevant range of superheats.Furthermore large-scale butane experiments werecarried out by INERIS (France) to ensure that for morerealistic scenarios the derived droplet size correlationsare accurate.Model validation and model improvements were carriedout by DNV Software, including validation of releaserate and initial droplet size against the above scaledand large-scale experiments. New refined correlationsfor droplet size distribution and Sauter Mean Diameter(SMD) were formulated and implemented into the Phastdischarge model. These were compared against arange of other droplet size and rainout correlationspublished in the literature, in conjunction with validationagainst an extensive set of experiments. It was shownthat the new droplet size correlation agrees betteragainst experimental data than the existing Phastcorrelation. To further improve the rainout prediction,the Phast dispersion model (UDM) was also extendedto allow simultaneous modelling of a range of dropletsizes and distributed rainout (rather than rainout at onepoint).