Experimental study on the evaporation and micro-explosion characteristics of nanofuel droplet at dilute concentrations

摘要

The evaporation and micro-explosion characteristics of nanofuel droplets were investigated using highspeed backlight imaging technique at 873 K and 1 bar. Cerium oxide (CeO2) nanoparticles were utilized as nano-additives at dilute concentration of 0.05% and 0.25% by weight added to diesel. The results showed that micro-explosion mechanism of DCe-0.05 and DCe-0.25 consisted of 8 distinct processes: first class bubble formation (caused by volatile components), porous spherical shell formation, second class bubble formation (caused by nanoparticles), agglomeration of bubbles, micro-explosion, steady evaporation, concentration of nanoparticles near the droplet surface, and compact spherical shell formation. However, only processes 1, 4, 5 and 6 occurred for diesel droplets. The evaporation rate of diesel droplets were significantly affected by nano-CeO2 concentrations. An increase in the evaporation rate with nanoparticle concentrations, but a decrease in the evaporation rate at steady evaporation stage. This is because the formation of a compact spherical shell on the droplet surface suppressed liquid fuel diffusion. The micro explosion delay of DCe-0.05 and DCe-0.25 decreased by 24.1% and 47.1% compared with diesel. Two new parameters were proposed for quantitative analysis expansion and micro-explosion characteristics, namely, expansion and micro-explosion intensity. The micro-explosion intensity of DCe-0.05 and DCe-0.25 increased by 37.5% and 49.5%, respectively. (C) 2019 Elsevier Ltd. All rights reserved.