Spray atomization characteristics of a low pressure rotary injector

Atomization increases the overall surface area of the fuel stream and improves evaporation and fuel-air mixing, thus leading to efficient and clean combustion. Fuel atomization and droplet dispersion play vital roles for achieving efficient combustion inside a spray combustor. A novel atomizer was developed which employs a rotating spindle with blades at the orifice exit to atomize the fuel into a fine spray. Important spray characteristics, e.g., spray cone angle and Sauter mean diameter were measured using a high-speed camera and a phase Doppler interferometer. This atomizer provides uniform fine sprays even at very low pressures of the order of 1 bar. The droplet size distribution and dispersion exhibit only minor dependence on the fuel flow rate or injection pressure. Criteria were identified for three different liquid break up modes, namely, jet break up, sheet break up, and direct drop formation. Useful correlations for evaluating the spray droplet size are presented in terms of the swirl number of liquid flow, rotational speed based sheet Weber number, and swirl air Reynolds number.