An improved non-equilibrium multi-component evaporation model for blended diesel/alcohol droplets and sprays

A non-equilibrium Langmuir-Knudsen model for multi-component pure diesel and blended diesel/alcohol sprays is developed and evaluated through comparisons with experimental measurements. This model takes into account most of the key processes during the droplet lifetime, including the finite heat conduction and limited mass diffusion inside the droplet, the differential diffusion in gas phase, as well as the non-equilibrium Langmuir-Knudsen evaporation law for multi-component droplets. Twenty discrete components are selected to represent the fuel. The present model shows good agreements with experimental measurements for pure ethanol, diesel, and blended diesel/ethanol droplets. Both equilibrium and non-equilibrium models perform nearly identically for low evaporation rate conditions. The nonequilibrium effects become significant when the initial droplet diameter is smaller than 20 μm, and these effects are enhanced with increasing ambient temperature and forced convection intensity. It is additionally observed that the non-equilibrium effects are more significant for the blended diesel/alcohol droplets than pure diesel, especially during the evaporation period of ethanol. The present evaporation model has been implemented into a multi-dimensional CFD code and applied to calculate the evaporation processes of singleand multi-component fuel droplets and sprays under various ambient conditions. The non-equilibrium effects for the blended diesel/alcohol sprays are also evaluated and proved to be significant for the fuel vapor component concentrations. ILASS-Americas 30th Annual Conference on Liquid Atomization and Spray Systems, Tempe, AZ, May 2019 2