Droplet vaporisation characteristics of vegetable oil derived biofuels at high temperatures
Résumé
To characterise the mechanisms occurring in the deposit formation during the combustion of vegetable oils used as biofuels in Diesel engines, it is necessary to investigate the vaporisation of vegetable oil droplets under various ¯ow, pressure and temperature conditions. In the current work, experimental results about the vaporisation of rapeseed and sun¯ower oil methyl ester droplets at high temperatures are presented. The ®bre-suspended droplet technique is used and the time evolution of droplet diameter during vaporisation is observed by imaging technique. Average and instantaneous vaporisation rates have been estimated from the d 2-curves at temperatures between 473 and 1020 K and at atmospheric pressure. The droplets of vegetable oil methyl esters evaporate like mono-component droplets with a very significant heating phase. A comparison with experimental results obtained with n-alkanes droplets (from n-pentane to n-decane) and prediction of the quasi-steady theory is also presented and discussed.