Modelling of biodiesel fuel droplet heating and evaporation: Effects of fuel composition

Abstract

A comparative analysis of predictions of several models of biodiesel fuel droplet heating and evaporation in realistic Diesel engine-like conditions is presented. Nineteen types of biodiesel fuels composed of methyl esters are used for the analysis. It is shown that the model, based on the assumption that the diffusivity of species in droplets is infinitely fast and the liquid thermal conductivity is infinitely large, under-predicts the droplet evaporation time compared with the model taking into account the effects of finite diffusivity and conductivity, by up to about 15%. A similar under-predictions of the model in which the transient diffusion of species is ignored and the liquid thermal conductivity is assumed to be infinitely large, is shown to be about 26%. The latter result is not consistent with the earlier finding, based on the analysis of only five types of biodiesel fuels and different input parameters, in which it was shown that the deviations between the evaporation times predicted by these models do not exceed about 5.5%. As in the case of Diesel and gasoline fuel droplets, for biodiesel droplets the multi-component models predict higher droplet surface temperatures at the final stages of droplet evaporation and longer evaporation times than for the single-component models. This is related to the fact that at the final stages of droplet evaporation the mass fraction of heavier species, which evaporate more slowly than the lighter species and have higher boiling temperatures, increases at the expense of lighter species.

Models for automotive fuel droplets heating and evaporation

“…Based on recent research findings (e.g. [3,[10][11][12][13]), the drawbacks in modelling fuel droplets heating and evaporation processes (computationally expensive models, ignoring temperature gradient and transient species diffusion) are partially addressed using the MDQD model. This paper summarises some comparisons between the results, referring to fuel droplet evaporation times and time evolution of droplet surface temperatures and radii, predicted by the previously suggested simplified models, the recently developed version of the DCM and the multidimensional quasi-discrete model (MDQDM) [14][15][16].…”

Droplets heating and evaporation: an application to diesel-biodiesel fuel mixtures

“…The full compositions of diesel and biodiesel fuels were considered. The diesel fuel consisted of 98 hydrocarbons and the 19 biodiesel fuels, TME, LME, BME, CME, PMK, PME, SFE, PTE, CSE, CNE, SNE, SME, RME, LNE, TGE, HME1, HME2, CAN and WCO, consisted of 11,8,14,8,11,10,4,8,7,8,7,7,8,6,7,13,7, 12 and 14 components of methyl esters, respectively. The effect of increasing biodiesel fuel concentration on the evolutions of droplet surface temperature and evaporation time was clearly illustrated.…”

“…In this paper, the discrete component model (DCM) (see [5][6][7]) is utilised to analyse the droplets heating and evaporation of diesel-biodiesel fuel blends. These blends are represented by a mixture of 19 types of biodiesel fuels with up to 17 species of methyl ester (see [8] for more details) and diesel fuel, formed of 98 hydrocarbons (see [7] for more details). The thermodynamic and transport properties of diesel fuel are inferred from [7]; while for properties of biodiesel fuel are taken from [9].…”

Introductory Chapter: Biofuels - Challenges and Opportunities

“…To conclude, the use of biofuels is expected to contribute to the energy sustainability and reduction of global warming. For instance, many efforts have been made to replace gasoline and diesel fuels with ethanol/gasoline and biodiesel/diesel fuel blends, respectively [11][12][13][14][15][16]. These efforts have been driven mainly by the importance of reducing greenhouse emissions and fossil fuel costs [17][18][19].…”