AN EXPERIMENTAL STUDY ON THE DROPLET VAPORIZATION: EFFECTS OF HEAT CONDUCTION THROUGH THE SUPPORT FIBER

International audienceDroplet vaporization process is of interest in energy systems such as diesel and rocket engines, in which the fuel is supplied as a spray of droplets. The classical "quasi-steady" theory has been developed within the context of isolated droplet vaporization studies and is also used in spray models because of its simplicity. This theory predicts a linear evolution of the squared droplet diameter with time and allows estimating the "droplet vaporization rate". The aim of this study is to provide a detailed description of the heat and mass transfer mechanisms occurring in the vaporization of isolated droplets due in particular to the presence of the droplet support fiber in most of the experiments. Most droplet evaporation and combustion experiments have been conducted with the droplet suspended on a support fiber to avoid the experimental difficulties for free-falling droplets, such as for obtaining high-resolution droplets images. The potential influences of the support fiber on the evaporation rate have been pointed out in previous studies, but in the absence of alternative solutions, most researchers continued to employ this method. The literature reports many studies appreciably improving the technique by reducing as much as possible the fiber diameter, others by taking into account in numerical models this phenomenon, then correlating their results with experimental data. It is only very recently that experimental studies, equivalent to the one presented here, could implement extremely fine suspension fibers, allowing the production of new results. In this paper, experimental measurements will be presented to highlight and discuss the effects of heat transfer through the support fiber on droplet evaporation. Different droplet sizes, fiber diameters and orientations, gas temperatures, and fuel volatilities have been tested and analysed