IMPROVING DROPLET BREAKUP AND VAPORIZATION MODELS BY INCLUDING HIGH PRESSURE AND TURBULENCE EFFECTS

This article reviews recent experimental work conducted at the Laboratoire de Combustion et Systemes Reactifs (LCSR), Orleans, France, on single droplet breakup and vaporization. Emphasis is essentially put on high pressure and turbulence effects. The experimental facilities developed and the diagnostics used are first presented. Droplet breakup studies are conducted with cryogenic and noncryogenic droplets subjected to aerodynamic shear forces under high-pressure conditions. The transition criteria between droplet breakup regimes, characteristic breakup times, and secondary droplet distributions are obtained for uniquely low values of the density ratio between liquid and gas phases and systematically varied values of droplet Weber and Reynolds numbers. Combined effects of high pressure and temperature on droplet vaporization are also systematically explored. The variation patterns of average vaporization rates with reduced pressure and temperature are conclusively established and compared to estimates from the quasi-steady model. The influence of turbulence on droplet vaporization rates is explored in detail. It is demonstrated that droplet vaporization rates increase significantly with turbulent Reynolds number, even when the droplet size is smaller than the turbulence integral length scale. Comprehensive correlations are established to take into account these various effects. Suggestions are made for ways of including these correlations as submodels into spray combustion numerical prediction codes and for future work to further improve them.