Experimental Study On Collision And Wall Collision Between Sub-millimeter Droplets

Collisions between droplets and wall collisions are widespread in everyday life.'In the fuel injection process inside the engine cylinder,collisions between the droplets and the collision of the fuel droplets against the cylinder wall are inevitable.The collision between the fuel droplets and the collision of the wall will directly affect the mixing quality of the oil and gas inside the cylinder and the production of the Coanda oil film,which will affect the thermal efficiency and pollutant emission of the engine.However,due to the limitation of experimental methods,most of the researches on collision and wall collision between droplets are based on the study of millimeter-scale droplets.Therefore,this paper uses submillimeter droplets as the research object,and uses high-speed photography technology to carry out submillimeter droplet collision.The research results can deepen the understanding of the collision and collision mechanism of droplets,thus providing an experimental basis for better atomization.The generation of micron-sized droplets has an important influence on sub-millimeter droplet collision and wall collision studies.In this paper,we firstly create a visual experimental system by constructing submillimeter droplets,and use a monodisperse droplet generator to produce sub-millimeter droplets.The effects of jet velocity,disturbance frequency and orifice diameter on the size,distribution and morphology of the submillimeter droplets produced were studied.It was found that the sub-millimeter droplets produced at a certain jet velocity and disturbance frequency can match the droplets.The experimental requirements of collision and wall impact control the droplet size and shape change.Secondly,research on collisions between droplets was carried out.The collision fusion motion between sub-millimeter droplets is analyzed,and the morphological change law after sub-millimeter droplet collision is obtained.In addition,the variation process of droplet collision oscillation and collision fragmentation and characteristic parameters during the collision fusion between submillimeter droplets and millimeter-scale droplets is analyzed.The collision velocity,droplet size ratio and droplet property parameters are obtained.The influence law of droplet collision oscillation and crushing motion.Finally,the article carried out an experimental study on the impact of submillimeter droplets on the wall.The changes of the movement state of the droplets when the droplets hit different wall conditions were explored.The rebound and the movement of the liquid droplets after the droplets hit the wet wall and the rebound and the crushing movement of the droplets after hitting the high temperature wall were analyzed.The influence of wall velocity,droplet size and droplet property parameters on droplet motion characteristic parameters.There are 112 figures,7 tables and 89 references in this thesis.