Optical diagnostics for W/O emulsification within impinging flow and right angle mini-channel

The emulsification is well known for being considered as a solution for improving biodiesel combustion. In this extent, the size of the dispersed droplets is crucial to favour micro-explosions and optimising the combustion. The present mini-channel operates liquid/liquid dispersion at higher flow rates than with usual implementations of minichannels and micro-channels. Due to this particular condition of functioning, the flow enhanced in the mini channel is classified as a high-speed emulsifying one. In this study, the dispersion of water into sunflower oil as a water-in-oil (w/o) emulsion is tested. In such an in-line process, high-shear implies higher velocities at smaller scales, making an optical visualisation difficult. But the light scattering technique enables to detect micro-scaled droplets, at the required high velocities. The proper design and exploitation of a focalised laser beam through a transparent, hydrophobic mini-channel is explained. A focalised laser beam is crossing the mini-channel, dealing with the scattering cross sections of the water droplets. The measurement of the collected beam is successfully matched to the geometrical properties of the emulsion (water fraction and size of inner droplets) through the classical light scattering theoretical basement. The calibration of the collected laser light technique obtained in the straight mini-channel is followed by measurements approaching the high shear rate zone of the cross-flowing mini-channel.