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

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

“…In general, increasing the mass fraction of DME for a droplet reduces the lifetime of the whole droplet, due to the higher evaporation rate of DME compared to a single component droplet of n-heptane. For the 75% DME droplet under T amb ¼ 723 K, a relative constant and high DME evaporation rate is maintained for 0.6 s/mm 2 from the start, because the two competing effects (heat transfer into droplet and consumption of latent heat) reach the thermal equilibrium [10]. However, the flat regions are not observed under T amb ¼ 923 K for the 75% DME droplet.…”

“…Here, the lifetime of a droplet is ended when 95% of the droplet has evaporated. The temperature dependent thermophysical properties for liquid and vapor species of DME and n-heptane can be referred to [10], and references cited therein. Fig.…”

“…The liquid phase is treated as a thermodynamically ideal fluid, using the UNIFAC method [15] for calculating the component activities, and the gas phase is treated as ideal. The model had been validated for the evaporation of DME/ n-heptane droplet in the previous work [10]. The properties of structure groups in different molecules of DME and n-heptane can be referred to the literature [10,16,21e23] and references cited therein.…”

“…DME fueled CIDI (compressionignition direct-injection) engines also generate less noise than conventional diesels [9]. With the increasing concerns on alternative fuels, it is essential to understand the effect of their different physical properties on combustion processes [10]. Law [5] proposed two models to describe the combustion of multi-component droplets, and he found that the components evaporated approximately sequentially in the order of their relative volatilities.…”

“…Brenn et al [15] proposed a multi-component model combined with UNIFAC (Universal Functional Activity Coefficient) approach, and investigated the evaporation characteristics of five-component droplets of ethanol, methanol, 1-butanol, nheptane and n-decane. Ju et al [10] investigated the effect of mass fractions on evaporation of a DME/n-heptane droplet at IC engine conditions, with the combination of UNIFAC method [15,16] and the non-equilibrium evaporation law [17,18]. Wang et al [19] analyzed the evaporation characteristics of a multi-component droplet consisting of n-heptane, n-dodecane and n-hexadecane.…”