Prediction Models of Droplet Characteristics Based on the Locally Convergent Configurations in PMMA Microchips

Abstract This paper novel designed the local convergence configuration in the coaxial channels to study the two-phase flow (lubricating oil (continuous phase, flow rate Q c )/deionized water (dispersed phase, flow rate Q d )). Two geometric control variables, the relative position ( x ) and tapering characteristics ( α ), had the different effects on the droplet formation. The increase of relative position x caused the higher frequency and finer droplets, and the increase of convergence angle α , took the opposite effects. The results indicated that the equivalent dimensionless droplet length L d /W out and the flow rate ratio Q d /Q c had an exponential relationship of about 1/2. Similarly, it was found that the dispersed droplets generating frequency and the two-phase capillary number, Ca TP = u TP μ c /σ , had an exponential relationship. The advantage of the convergent configurations in micro-channel was the size and efficiency of droplet generation was very favorable to be controlled by α and x .