Secondary atomization characteristics of biofuels with different physical properties

A novel processing technique developed previously has now been automated and extended so that the complex shapes of fluid elements that dominate the secondary atomization process of mono-dispersed droplets in a constant velocity cross flow are classified and quantified. The experiments are conducted using high speed microscopic backlit imaging along with a calibrated image processing code, in conjunction with Laser Doppler Anemometry/Phase Doppler Anemometry (LDA/PDA) where applicable. Diesel, ethanol and a broad range of biodiesels with different flow-ability properties are investigated under a range of Weber numbers corresponding to bag, multi-mode, sheet stripping, and catastrophic breakup regimes. Using the parent droplet diameter and the object aspect ratio, the liquid filaments are classified into small spherical drops, larger objects and ligaments. It is found that at lower Weber numbers (We<100), fuel type influences the total breakup as reflected by the probability of detecting each of the three fragment types. The distinction is less clear at higher We where the probabilities for detecting various fluid shapes are similar for all fuels used here.