EFFECT OF ATOMIZING AIR FLOW ON SPRAY ATOMIZATION OF AN INTERNAL-MIX TWIN-FLUID ATOMIZER

The effect of the atomization air flow rate on the spray characteristics of a swirling twin-fluid atomizer operating on Diesel fuel is investigated. The mean droplet axial velocity and size distributions were simultaneously measured using a phase Doppler anemometer (PDA). The mean droplet diameter is found to increase with radial distance from the spray centreline, while its axial velocity decreases from a peak at the centreline. Increasing the atomizing air-liquid fuel mass ratio (ALR) reduces the fuel droplet size due to the increased shear and increases the spray penetration length as a result of increased momentum. Comparison of the drop size-ALR relations to previous independently developed correlations shows good agreement. A comparison was made between the observable boundaries obtained with Mie scattering and the droplet number density. It is found that the Mie images correspond to 95%-99% edge of the cumulative droplet mass distribution through the spray.