TURBULENCE EFFECTS ON THE VAPORIZATION OF MONOCOMPONENT SINGLE DROPLETS

An experimental facility has been developed to study the effects of tu rbulence on droplet vaporization. The facility allows to generate a ze ro mean velocity, isotropic and homogeneous turbulence and to vary sys tematically the turbulence kinetic energy. The influence of turbulence on suspended single droplets of five n-alkane hydrocarbons is investi gated, by determining the average vaporization rates by image analysis techniques. The experiments have been conducted under normal pressure and temperature conditions; for all cases, the length scales of energ etic turbulence eddies are larger than the initial droplet diameter. F or all the investigated cases, it is found that the presence of turbul ent velocity fluctuations increases the average vaporization rates com pared to the stagnant case. The linear regression rate of the projecte d droplet surface area versus time is observed under all turbulence co nditions. It is observed that droplets of the five investigated fuels respond differently to the same turbulence structure. A given turbulen t kinetic energy enhances more strongly the average vaporization rates -of lowest volatility fuels. Also, for each fuel, the normalized vapor ization rate tends towards a plateau behavior for increasing turbulenc e kinetic energy. The experimental information collected in this study has been used to suggest a phenomenological model For the turbulence effects on monocomponent droplet vaporization. The model explains this effect in terms of the ratio between a turbulence diffusivity and the molecular diffusivity of the fuel vapor.