Shock Tube Measurements of Water and n-Dodecane Droplet Evaporation behind Shock Waves

Abstract

Measurements of the evaporation rates of aerosols consisting of micron-sized droplets using near-infrared laser extinction methods were performed in a new aerosol shock tube. These experiments represent the flrst high-temperature measurements of evaporation using Mie extinction techniques with IR diode lasers. Mixtures of water or n-dodecane droplets with diameters in the range of 1{10 „m were heated and compressed behind incident shock waves in argon at temperatures between 475 and 870 K and pressures of 0.6{1.8 atm. Droplet size distribution and loading were monitored using a wavelength-multiplexed laser diagnostic using four lasers with wavelengths at 0.612, 1.33, 1.62, and 2.05 „m. From these Mie extinction measurements, the pre-shock size distribution and loading were determined before the arrival of the incident shock and the d 2 evaporation law rate constants for these distributions were determined behind the incident shocks. Good agreement with previous lower-temperature water evaporation measurements was found. We believe these are the flrst n-dodecane evaporation rate measurements for micron-sized droplets.