Study Of The Flow And Heat Transfer And Splash Characteristics Of Oil Droplets Impacting With High Temperature Solid Wall

In industrial production,the safe operation of machinery and equipment requires correct lubrication.High-speed rotating machinery and typical transmission parts(bearings,gears,etc.)are mostly lubricated by oil mist lubrication,splash lubrication,drip lubrication,etc.Lubricating oil is sprayed onto the surface of the parts in the form of oil droplets,which are deposited to form oil film after colliding with the surface of the parts,and the flow of the oil film is spread to take away the heat from the surface of the high-temperature parts to achieve the lubrication and cooling function of the mechanical parts.In many cases,oil droplets collide with the surface of high temperature part and then splash,forming a certain number of secondary oil droplets,which also affect the lubrication and heat dissipation of the parts.An in-depth understanding of the complex flow and heat transfer behaviour of oil droplets as they interact with the surface of the high-temperature parts is essential for the correct lubrication design and analysis of mechanical parts.Based on this,this paper carries out research on the flow and heat transfer and their splash characteristics of oil droplets colliding with high temperature solid wall.Through numerical calculations and experimental research,the flow spreading and heat transfer behaviour of the deposited oil film after the impact between oil droplets and high temperature solid walls,as well as the splash mechanism and splash characteristics are explored,and a critical criterion for oil droplet splash is established.The main research work is as follows:(1)Based on the physical process of oil droplet impact with high temperature solid wall,the influence of temperature on the thermodynamic characteristic parameters of oil fluid is analysed,the dynamic change of contact angle during the flow spreading of deposited oil film is described by Hoffman function,and the flow and heat transfer theoretical analysis model of oil droplet impact with high temperature solid wall is established by combining the basic theories of fluid dynamics and heat transfer.(2)The VOF(Volume of Fluid)method is used to dynamically track the interface between the oil droplet(oil film)and the air,and the flow and heat transfer theoretical analysis model of the impact between the oil droplet and the high-temperature solid wall is combined with the flow and heat transfer theoretical analysis model of the impact between the oil droplet and the high-temperature solid wall,and the three-dimensional numerical calculation models of the flow and heat transfer between the oil droplet and the high-temperature solid wall are established respectively.The flow and heat transfer characteristics of the deposited oil film,and the formation mechanism and splash characteristics of the secondary oil droplets after the normal and oblique impact of oil droplets with the high temperature solid wall are analysed respectively,and the effects of changing the oil droplet impact conditions on the flow and heat transfer of the deposited oil film and the splash characteristics of the secondary oil droplets are discussed.(3)A experimental apparatus for the impact between oil droplets and high-temperature stainless steel wall was designed and constructed,and experimental studies on the normal and oblique impacts between oil droplets and high-temperature stainless steel wall were carried out.A high-speed camera was used to photograph the impact between oil droplets and hightemperature stainless steel wall and the subsequent flow spreading of the deposited oil film and oil droplet spattering process,and the spreading diameter of the deposited oil film was measured by image processing techniques to obtain the morphological evolution of the deposited oil film from spreading to splashing.