# Analysis of Grinding Flow Field under Minimum Quantity Lubrication Condition
###### Abstract  
The flow field around the grinding wheel prevents grinding fluid from entering the grinding area, which deteriorates machining conditions and reduces the quality of the workpiece. MQL (Minimum Quantity Lubrication) grinding uses compressed gas to improve the ability of the grinding fluid to pass through the flow field of the grinding wheel so that a small amount of the grinding fluid can meet the cooling and lubrication requirements and reduce the cost of using grinding fluid. In this study, we investigated the flow field of grinding wheels under MQL conditions and obtain the rules that influence factors such as grinding fluid flow rate, grinding wheel linear speed and compressed gas pressure affect the flow rate of grinding fluid. The simulation method was used to simulate the flow field of the grinding wheel and the trajectory of the grinding fluid droplets. The simulation results show that these factors are important ones affecting  
obstruct the grinding fluid from going into the grinding area. Moreover, the reflected flow enhanced with the increase in the rotational velocity of the grinding wheel and weakened with the decrease in the gap between the grinding wheel and the workpiece. [PERSON] and [PERSON] [16] established a heat distribution model considering the influence of MQL jets. On the basis of this and the moving triangular heat source model, a model which can predict the grinding temperature was established. In the model, the MQL jet is considered as a homogeneous two-phase fluid in the flow cross-sectional area which have equal liquid, gas velocities and temperatures. However, in the presence of viscous force, droplets adhere to the workpiece surface and separate from compressed air. Thus, in the grinding zone, the MQL jet should not be considered as a homogeneous two-phase fluid. On the basis of the boundary layer theory, [PERSON] et al. [17] studied the effect of minimum quantity lubrication of nanofluids on surface grinding temperature and developed a convective heat transfer coefficient model. Using computational fluid dynamics simulation technology, [PERSON] et al. [18] studied the interaction between cooling jet and air field, which is helpful for improving the understanding of the interaction between the grinding wheel, air field and grinding fluid. [PERSON] et al. [19] studied the pressure change in the grinding wheel flow field under different parameters, and the formation of the gas barrier layer. A pneumatic barrier device was designed to restrain the grinding wheel gas flow field, so as to improve the utilization rate of grinding fluid.  
Although there is much research on the flow field of the grinding wheel and MQL, few scholars have studied the flow field of grinding wheel under the MQL conditions, and there is a lack of research on the influence of the grinding wheel flow field on the MQL jet entering the grinding zone. In fact, the ability of the MQL jet penetrating the flow field of grinding wheel is the key factor to determine the cooling effect of MQL. The distribution of the flow field in the grinding wheel has a great effect on the movement of the MQL jet. Also, it determines whether the MQL jet can enter the grinding zone.  
In this study, in order to investigate the flow field of grinding wheels under MQL conditions and obtain the rules that how the influence factors affect the flow rate of grinding fluid and the grinding temperature. The discrete term simulation model is used to simulate and analyze the flow field of grinding wheel under the MQL conditions based on computational fluid dynamics. The gas in the grinding area is taken as the continuous phase, and the MQL droplet as the discrete phase. The effect of micro-lubrication parameters, such as gas pressure, grinding fluid flow, etc., on the effective flow of the grinding fluid into the grinding area is deeply explored.