Bicomponent droplets evaporation: Temperature measurements and modelling

Development of improved energy conversion systems, having higher efficiencies and lower emissions, is central to reducing the production of green-house gases and to meeting air quality standards for other emissions. In non-premixed combustion systems, vaporization of the droplets and mixing of the vapour with the surrounding oxidizer control the overall rate of energy release. Droplet vaporization is affected by the nature of the liquid petroleum that contains species having extremely different volatilities. A fine understanding of multi-component droplet vaporization is therefore an important issue to optimize the combustion systems. This paper presents the application of a recently developed technique to measure the temperature of bi-component droplets. Based on the three-color laser-induced fluorescence (LIF) technique, droplet temperatures can be measured regardless of the composition. The method requires adding a small amount of a fluorescent organic dye to the fuel which is composed of ethyl-alcohol and acetone. The accuracy of the measurement is about ±1.3 °C. In this study, the emphasis is placed on the evaporation of the binary mixture in a hot air plume, the temperature of which (around 650 °C) largely exceeds the boiling point of the liquid components. An extensive study of the influence of the initial composition and droplet diameter is carried out. Finally, the experimental results are compared to an evaporation model based on the discrete components approach.