Mo­lecu­lar sim­u­la­tion study of droplet ther­mo­dy­nam­ics un­der ex­treme am­bi­ent con­di­tions

Droplets occupy a prominent position in nature, e.g. in the form of rain, clouds and fog. For energy applications, droplet evaporation is the dominant mechanism in spray atomization occurring in internal combustion and jet engines. In such cases the liquid phase is immersed into extreme ambient conditions of high temperature and pressure. High pressures are favourable to be generated immediately after the injection of a fuel mixture into the engine in order to accelerate its atomization, which in turn creates much more surface area compared to the volume and thus enhances the evaporation process. Although these processes are commonly used, their fundamental understanding is, for the most part, lacking. An advanced physical understanding of all processes involved is mandatory in order to optimise technological systems and increase their efficiency. This was the main motivation behind the creation of the “Sonderforschungsbereich” Transregio 75 (SFB-TRR 75), which brings together scientists of a variety of institutes from the universities in Stuttgart, Darmstadt and the DLR Lampoldshausen, as well as from diversified backgrounds ranging from mathematics, physics, chemistry and computer to engineering science. The entire project is fully funded by grants of the Deutsche Forschungsgemeinschaft (DFG). According to each academic background, every member of this Transregio is assigned to one of the different sub-projects.  It is this interdisciplinary combination of expertise which allows achieving the ambitious goal to gain and extend a fundamental understanding of droplet dynamics. ThEt acts as an associate partner while its contributions are twofold, out of which one is to compute fluid properties (e.g. gas solubility, surface tension) for relevant substances (e.g. acetone, oxygen, nitrogen) via equilibrium molecular dynamics simulations as well as experiments. Furthermore, the evaporation of nanoscale processes is modelled via appropriate methods using non-equilibrium molecular dynamics simulations.