| Hydrodynamic pressure of coolant is generated in the converged area while coolant flows into the zone between grinding wheel and workpiece. This hydrodynamic pressure, on the one hand, indicates whether the coolant supplied is sufficient. On the other hand, it illustrates how much the normal force exerted on the grinding wheel is. More active researches have been made in these two respects recently. Therefore, it is of great importance to catch on the distribution of hydrodynamic pressure within jet zone and grinding zone.However, through the analysis of the status quo about coolant hydrodynamic pressure, this paper finds out some limitations to the study of coolant hydrodynamic pressure in existence in such three aspects as theory of fluid dynamics adopted, mathematical models constructed and assumptive conditions given. Considering these problems, this paper makes theoretical studies and experimental researches on coolant hydrodynamic pressure of grinding, systematically.In theory, gas-liquid two-phase flow is selected to explore the distribution of coolant hydrodynamic pressure. And then, the method of VOF is inducted into the mathematical model to build up an instantaneous model describing properties of gas-liquid two-phase flow field, which emerges in due course of coolant jetting into gas flow field. Finally, the instantaneous model is solved out in the case of no special pressure conditions exerted on the outlet boundary.In experiment, the system of grinding jet for cooling is designed, and three kinds of nozzles are employed to supply coolant in surface grinder of MM7125. Three purposes of this experiment are: (1) To verify the effectiveness of this instantaneous model of gas-liquid two-phase flow. (2) To explore the relationship between hydrodynamic pressure of gas-liquid two-phase flow and jet velocity of nozzles. (3) To collect experimental results to be used as training samples and test samples for the predictive model of grinding jet for cooling.On the basis of the above studies, one evaluation index of cooling effect is advanced, which is a ratio of the maximum hydrodynamic pressure of gas-liquid two-phase flow to the maximum hydrodynamic pressure of liquid one-phase flow. Moreover, the predictive model of grinding jet for cooling based on ANN is constructed.To calculate the maximum hydrodynamic pressure of liquid one-phase flow, this paper carries out a research for the properties of liquid one-phase flow field. With the result that mathematical model for laminar flow and mathematical model for turbulent flow are built, respectively. Accordingly, the hydrodynamic pressure distribution of liquid one-phase flow and maximum hydrodynamic pressure are obtained.The maximum pressure of gas one-phase flow will be used for reference to fix the critical jet velocity of nozzles. For this reason, mathematical model describing properties of gas one-phase flow is built and solved with gas pressure distribution and maximum pressure gained.It is feasible and effective to employ gas-liquid two-phase flow in the study of hydrodynamic pressure of grinding fluid field in that results of experiments agree by and large with numerical results of calculations.From the foregoing the following conclusions can be drown: (1) Coolant exiting the grinding zone is attached to the surface of grinding wheel, not to the surface of workpiece. (2) Coolant entered into the grinding zone is attached to the workpiece surface, not to the surface of grinding wheel, facilitating to convection heat transfer. (3) It will make no sense to increase jet velocity of nozzles when the velocity comes to a certain value. (4) The original cooling system of MM7125 surface grinder with grinding wheel rotating at the speed of 44m/s is to be modified due to poor cooling effect. (5) The predictive model of grinding jet for cooling based on ANN can be applied both in the test on line during grinding and in navigating coolant delivery for optimization.To sum up, all of the researches in this paper will go a good way with application and development of intelligent grinding in the near future.
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