Experimental investigation on single drop breakage in two-stream impinging microchannels

Experimental study on drop breakage is carried out in the microchannels utilizing head-on impingement configuration by observing a single drop breakup process. In this study, the breakage of oil drops with a diameter ranging from 30 to 200 μm is investigated in the vicinity of flows impingement region by using high-speed photography at varied flow rate conditions. The most prominent phenomenon of the single drop breakup in the two streams impinging flow field is that the drop tends to break into multiple fragments. The breakage time and the number of daughter drops in the resulting population are statistically analysed and found to be highly dependent on the mother drop size and energy dissipation rate. Two different micro-system geometries, the 600–600 system and the 600–300 system, are compared to evaluate the advantages and disadvantages of swirl flow developed due to the off-axis layout of inlet channels in the 600–300 system. The results show that swirl flow establishes a low-pressure area acting as the dead zone, where a drop can be trapped and then drastically stretched to breakup. Compared with the 600–600 system, the detrimental effect of swirl flow inside the 600–300 system on increasing the breakage time can be offset by a much greater amount of daughter drops generated. In general, the 600–300 system performs more effectively than the 600–600 system because of the less isotropic flow feature. And this superiority is more distinct when the energy dissipation rate is higher.