| The phenomenon of droplets impacting on liquid film can be seen in a variety of scenarios in nature and industrial production,especially in the combustion chamber of internal combustion engines,which has an important impact on the combustion efficiency.In industry,more and more biomass fuels are used in combustion equipment.Therefore,mastering the dynamic behavior and kinematic of biomass oil droplet impacting liquid film is of great significance for improving the combustion efficiency of internal combustion engines.Relying on the Zhejiang Provincial Natural Science Foundation Project(LY15E060007),on the self-built droplet impact platform,the experimental research of biomass oil droplet impacting on immiscible liquid film was carried,the morphological characteristics and dynamics were analyzed.The main work are as follows:(1)Morphological characteristics of crown formed by biomass oil(camellia oil,ethanol,and water)droplet impact on liquid film is analyzed.The effect of physical properties on the dynamic behavior of crown is emphatically analyzed.For the crown radius,on the basis of discussing three critical We,the crown radius and its average spreading velocity were compared with the previous theoretical models,and the applicability of camellia oil to immiscible liquids was discussed.The maximum characteristic height of crown increases with We,which is slightly affected by the film thickness at lower We,but decreases with increasing film thickness at higher We.(2)crown evolution kinematics of a biomass oil droplet impacting on liquid film is analyzed,including crown spreading/rising velocity and acceleration.The spreading ability of crown in radial and vertical directions is expressed by the ratio of crown rising and spreading velocity.The dimensionless average spreading velocity decreases with We and follow a multivariate power law,while the dimensionless average rising velocity remains constant.Radial motion plays a dominant role in crown evolution at low We,however its influence decreases with increasing We.The velocity ratio(β)has a linear relationship with the increase of We,indicating that the crown rising motion is gradually enhanced with the increase of We,and the rising kinetic energy is still smaller than that of spreading in the radical direction.(3)The morphological characteristics of the Worthington jet generated by biomass oil droplet impact on liquid film and the critical curve of Worthington jet break-up is analyzed.When jet breaking up,the effects of physical properties,film thickness and We on breaking morphology were discussed.The experimental results show that the film thickness has a great influence on the break-up characteristics,and the ethanol active range is 1.56～2.15,in this range,the break-up characteristics are more obvious.Moreover,the maximum rebound height of ethanol jet was Gaussian distribution with the increase of film thickness.The base diameter of camellia oil and water increased with time,and the base diameter of ethanol increased first and then decreased with time.(4)The Worthington jet kinematic of biomass oil droplet impacting on liquid film was preliminarily discussed.Analyze the velocity and acceleration of Worthington jet.The results show that the outlet velocity of Worthington jet increases with We and gradually tends to be stable.Acceleration decreases with time and finally stabilizes.The innovation of this paper lies in: defining the critical dimensionless parameters of whether crown and jet are generated or not after biomass oil droplet impact the liquid film;the distribution of the kinetic energy of the droplet in the vertical direction and in the horizontal direction are revealed;a concise and practical crown velocity distribution law of multivariate power function distribution is proposed.The results provide experimental basis for the intensive study of the impact behavior characteristics of biomass oil droplet,and have important practical significance for the efficient and clean utilization of biomass liquid fuel. |
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