Flash boiling explosion model of dimethyl ether (DME)/n-pentane bi-component droplet under gasoline engine conditions

Abstract

The flash boiling explosion model that integrates the sub-processes of the boiling period, including the homogeneous nucleation sub-model, the bubble growth sub-model and the boiling explosion sub-model, is proposed to investigate the evaporation and explosion characteristics of a superheated bi-component droplet under gasoline engine conditions. The bubble point pressure is discussed based on the Wilson approach. The dependence of physical properties on the temperature and the concentration is considered. A comprehensive bubble growth model is developed to predict the bubble growth and evaporation of the DME/n-pentane droplet with different mixing ratios. Two criteria in parallel are employed to predict the time of boiling explosion. The result shows that a larger DME mixing ratio and higher liquid temperature can decrease the duration of the surface tension controlled stage, expedite the bubble growth, and consequently shorten the boiling explosion time. A higher DME proportion can improve the evaporation rate of DME, meanwhile, the peak value of the evaporation rate is shifted to an earlier moment at a fixed droplet temperature. Furthermore, the boiling explosion time map illustrates the appropriate region of the temperature and the mass fraction of DME for the flash boiling explosion.