Effect of mass fractions on evaporation of a multi-component droplet at dimethyl ether (DME)/n-heptane-fueled engine conditions

Two fuels with the compression-ignition property similar to conventional diesel-DME and n-heptane-are selected to analyze the evaporation performance of a two-component droplet at different internal combustion engine conditions. A multi-component evaporation model based on Universal Functional Activity Coefficient (UNIFAC) method and the non-equilibrium evaporation law is implemented to predict the evaporation characteristics of the DME/n-heptane droplets with different mass fractions. Generally, reducing the mass fractions of DME, increasing the ambient temperature or increasing the relative velocity between the droplet and the ambient air enhances the evaporation of a droplet. However, the variation of the ambient pressure does not affect much on the lifetime of a DME/n-heptane droplet. It is interesting to find that a relative constant and high evaporation rate of DME can last for a relative long time with an appropriate mass fraction of n-heptane. It proposes a way to change the evaporation rate of each component by altering the mass fractions in the DME/n-heptane mixture, in order to control the combustion of DME/n-heptane blended fuels.