Internal Temperature Distributions of Vaporizing Droplets: Effect of Their Spacing

A line of mono-sized and periodically spaced droplets is moving in the diffusion flame sustained by the droplet fuel evaporation. The temperature field within the droplets is measured using the two-color laser induced fluorescence technique. Experiments are undertaken on droplets made of different fuels including acetone, ethanol, 3-pentanone, n-heptane, n-decane and n-dodecane which have very different volatility and viscosity. A simplified model of the heat transfer within the droplet is developed, taking into account both heat conduction and heat advection by the droplet internal fluid circulation. Streamlines are assumed to follow those of a spherical Hill vortex, the intensity of which can be related to the friction coefficient. Comparisons between the measurements and the simulations reveal that the heat convection within interacting droplets is strongly reduced compared to the model of the isolated droplet.