On the evaporation rate of single fuel droplets due to isotropic ambient turbulence

Previous experimental results on the evaporation of single fuel droplets due to forced convection with isotropic ambient turbulence are extended. Test fuels include pentane, hexane, heptane, octane and decane with Reynolds number in the range of 72-250 based on initial droplet diameter and relative velocity between droplet and free stream. Variations of ambient turbulence properties were achieved by a low-speed vertical wind tunnel with different turbulence intensities and scales, controlled by using different sizes of disk. The free-stream turbulence intensities are varied in the range from 1% to 60% and the integral length scales are from 2.5 to 20 times of the initial droplet diameter. Results show that the time history of droplet diameter follows the d²-law in turbulent environments with generally higher evaporation rates as compared with those in quasi-laminar cases. Normalized evaporation rate (to quasi-laminar case) due to turbulence is reasonably correlated with Da_v. In addition, two distinct regimes separated by Da_v≈O.l are identified. For Da_v<0.1, normalized droplet evaporation rate increases with decreasing Da_v, while it is nearly the same as that in quasi-laminar environment for Da_v>O. 1.