Influence Of Surfactant On Drop Formation

The research background is coal-water slurry gasification technology in this thesis.The influence of surfactant on liquid drop and suspension drop formation is investigated experimentally by a high-speed camera and related image processing software.Main research contents were summarized as follows:The morphological characteristics of drop,the growth velocity and the fluctuation of velocity are impacted by the surfactant.When the surfactant concentration is smaller than critical micelle concentration(CMC),the thinning rate of neck diameter and the diameter of formed drop reduced with increasing of surfactant concentration.The breakup length and the growth velocity increase dramatically with increasing of surfactant concentration.When the surfactant concentration is bigger than CMC,the breakup length keep 11mm,the diameter of formed drop is 4.4mm,and velocity of drop is about 0.35m/s.We build the model of the growth velocity based on the dynamic surface tension.The fluctuation of growth velocity reaches maximum because the surface tension changes rapidly when the surfactant micelles transfer to the air-liquid interface.The morphological characteristics of suspension drop is effected by surfactant when Oh<1.The thinning rate of neck diameter and the diameter of drop reduce with the increasing of surfactant concentration.The breakup length and the growth velocity increase slightly when the surfactant concentration is high.The fluctuation of growth velocity is disappeared.The morphological characteristics of suspension drop are affected by nonionic surfactant significantly.When Oh>1,surfactant has little influence on the time evolution of neck diameter at the two pinch-off areas when the liquid viscosity is high.