Droplet dynamics of an auto-ignition burner with dense spray boundary conditions

Combustion and droplet dynamic characteristics of an atomizing spray of ethanol issuing in a vitiated co-flow are presented. Laser/phase Doppler anemometry, time averaged photographs and microscopic imaging are performed in order to characterise the boundary conditions and key features of the flow. Two regimes are noted, the dilute spray flame, and `dense’ spray flame regimes which dictate how the flame varies with the fuel/air ratio. The level of atomization in the spray is found to significantly affect the boundary conditions to a degree such that utilization of microscopic imaging and advanced image processing techniques is necessary in order to provide information otherwise rejected by conventional phase Doppler anemometry measurements such as non-spherical liquid fragments. Differently shaped liquid fragments will vaporize and atomize at different rates thereby affecting downstream combustion characteristics and this paper provides a selection of quantitative data which classifies such objects.