Modelling liquid jet atomisation with sub- and super-critical phase transition – SUB SUPER JET

The aim of this project is to develop a theoretical approach and associated computer code for Large-Eddy Simulation (LES) of liquid jet fragmentation and atomization in all thermodynamic conditions, from subcritical to supercritical pressure and temperature conditions. The transition between sub and supercritical conditions will be considered through a new and unified model, able to deal with capillary effects, phase transition between a liquid and its vapour as well as the dynamics of supercritical fluids. These different regimes of fuel jet dynamics are found in liquid rocket as well as Diesel engines depending on the combustion chamber temperature and pressure conditions. The situation is possibly already prevailing in current aircraft engines or will be reached in the future as the chamber pressure is being increased.
For sufficiently low pressure and temperature with respect to the critical point, the fluid undergoes a classical break-up process. The interface separating liquid and gas phases is discontinuous and droplets appear as the final stage of fragmentation. As pressure is increased to supercritical conditions, the phase discontinuity is no longer present. The jet evolves in the presence of a continuous interface and mass transfer takes place through turbulent fluxes and the process is analogous to mixing of variable density jets. It is planned to deal with all these aspects in LES and DNS frameworks. Such a unified approach has never been considered in the author’s knowledge as phase transition modeling in arbitrary flow conditions is a true scientific challenge.