Heat Transfer Characteristics Of Electrostatic Minimal Quantity Lubrication And Its Influence On Cutting Temperature

With Minimal Quantity Lubrication(MQL)technique,lubricant mixed with compressed air to form micron droplets is used to lubricate and cool the machining zone,decreasing the consumption of cutting fluids while ensuring the processing quality.MQL usually uses a vegetable oil lubricant for considering the point of environmental protection,health and safety.Compared to aqueous cutting fluid,the specific heat capacity and thermal conductivity of lubricating oil is much smaller which leads to a bad cooling performance in cutting.Electrostatic Minimal Quantity Lubrication(EMQL)technique,which is using synergetic effects between electrostatic spraying and MQL,was developed to improve the lubrication and cooling performance in machining.In this paper,for the heat transfer characteristics and cutting temperature of the electrostatic minimal quantity lubrication is researched.The main work and achievements are as follows:1.The droplet velocity,size and distribution,surface tension and contact angle are the important factors which affect the heat transfer performance of spray cooling.With oil lubricant charged,the droplet size,surface tension,contact angle was significantly reduced,the droplet number in same volume increased and the droplet velocity also has a certain growth,these help to improve the EMQL heat transfer capacity.2.By the transient and steady state heat transfer experiments,the effects of EMQL parameters(charging voltage,gas pressure,oil flow rate and spray distance)on the heat transfer characteristics were researched.The contact area of the charging droplets with heat transfer surface is increased,the impact and disturbance to the heat transfer surface is strengthened,and the evaporation and phase change also become much intense.Thereby increasing the critical heat flux of spray cooling system,enhanced the evaporation and forced convection heat transfer capacity of heat exchanger area.According to the heat transfer experiment results and combined engineering applications,at the condition of supply pressure0.3 MPa,spray distance 20 mm,charging voltage-15 kV,EMQL can get a better cooling and heat transfer capacity.3.Using cutting temperature,cutting force,surface roughness and tool wear as the standard to evaluate cooling and lubricating properties under three different conditions(dry cutting,MQL,EMQL).The results showed that EMQL droplets penetrate into the cutting area more effectively which can enhance the evaporation or phase change,reduce the cutting temperature,improve cooling and heat transfer performance and can significantly reduce cutting forces surface roughness and tool wear at same time.