Measurement of interacting ethanol droplets evaporation at moderately elevated temperature and pressure using phase rainbow refractometry

Abstract

Evaporation characteristics of interacting fuel droplets under the joint effect of ambient pressure, temperature and droplet size and spacing are critical to combustor design and simulation validation. This work reports an experimental study of evaporating monodisperse ethanol droplets at moderately elevated temperature (up to 673 K) and pressure (0.1-1.0 MPa). Evolution of droplet size and temperature along the measurement line and its evaporation rate were simultaneously measured using recently developed phase rainbow refractometry. The respective effects of the ambient conditions and droplet interactions on the heat and mass transfer of droplets were jointly studied. The results suggest that at lower ambient temperatures the droplet evaporation rate decreases with increasing ambient pressure. While at higher temperatures, the trend is reversed. Moreover, the dimensionless spacing parameter C of the droplets was well controlled to investigate the effect of inter-droplet interactions on evaporation under different ambient conditions. Strong droplet interactions, significantly inhibiting the droplet evaporation, were found to be influenced by ambient pressure. For the specific condition of droplet evaporation under low ambient temperature (373 K) and high pressure (1.0 MPa), the evaporation rate of droplets with C = 1.85 decreases by 19.1 % compared to droplets with C = 3.73. Furthermore, the correlations for Nusselt and Sherwood numbers are inferred by parametric study of the influence of the involved characteristic numbers.