Multicomponent evaporation model for pure and blended biodiesel droplets in high temperature convective environment

Biodiesel and more often its blends have been extensively used to mitigate the dependence on fossil fuel and the greenhouse gas emissions. However, a good understanding of the impact of the difference in the thermophysical properties of biodiesel and its blends from those of petroleum diesel is required to reap the benefits of biodiesel utilization. In this study a multicomponent evaporation model has been developed for pure and blended biodiesel droplets to investigate their evaporation characteristics in high temperature convective environment as encountered in practical combustion systems; and it is validated through a comparison with experimental results. The vaporization characteristics of pure diesel, pure biodiesel fuel droplets as well as the effect of mixing them in different proportions (B20 and B50) are presented. The results reveal that biodiesel droplets evaporate at a slower rate than the diesel droplets because of biodiesel’s relatively low vapor pressure. Consequently, the blending of diesel fuel with small proportions of biodiesel results in an increase in the evaporation timescale of the blended fuel droplets. Diffusion in the liquid phase is observed to be the rate controlling factor for blended droplet vaporization. The possibility of internal gasification for blended droplets is also investigated. A droplet with higher quantity of diesel is more prone to undergo internal gasification but micro-explosion is not likely to occur at atmospheric pressure.

► Developed a multicomponent vaporization model for pure and blended biodiesel droplets.
► Considered the inequalities in the gas phase diffusivities in the validated model.
► Confirmed the prolonging effect of biodiesel fraction on blended droplet lifetime.
► Showed the effect of diffusion coefficient on droplet vaporization time & temperature.
► Demonstrated the role of diesel fraction on blended droplet internal gasification.