VOF Simulation In Silicon Rod Grinding Process And Grinding Wheel Structure Improvement

The technology that converts solar energy into electricity is called photovoltaic power generation,and its most basic element is the silicon solar cell.Qualified solar silicon wafers must maintain certain shape and dimensional accuracy.In actual production,end-face diamond grinding wheels are often used to grind silicon rods to meet the accuracy requirements.In the process of grinding with end-face diamond wheel,grinding wheel and silicon rod constantly friction,grinding zone will generate a lot of heat,the usual method is to provide sufficient grinding fluid.However,when the grinding wheel rotates at high speed,the surface of abrasive ring will form an air boundary layer with certain pressure,which is called "air barrier".The existence of air barrier prevents the grinding fluid from entering the grinding zone effectively to participate in the cooling,and the grinding heat cannot be dissipated in time.Too high grinding heat will affect the service life of the grinding wheel and the surface quality of the silicon rod.Therefore,the study of airflow field characteristics of gas-liquid twophase flow in grinding zone has important guiding significance for practical production.In this thesis,the airflow field and gas-liquid two-phase flow field in the process of grinding silicon rod with end-facing diamond wheel were taken as the research object.Firstly,a model was established according to the actual grinding conditions.Based on computational fluid dynamics and multiphase flow theory,the multiphase flow model(VOF)in FLUENT finite element simulation software was used for numerical calculation.The distribution of airflow field and grinding fluid in the grinding zone is simulated during grinding.By changing grinding conditions,the influence of factors such as pouring amount of grinding fluid,grinding wheel speed,abrasive ring thickness,relative position of inner runner hole and rectangular through-groove and number of rectangular through-groove on flow field distribution in grinding zone was discussed,and several methods were put forward to increase cooling and cleaning effect in grinding zone.According to the VOF simulation research in grinding process,a new grinding wheel structure with a non-through groove in the inner part of abrasive ring along the radius direction was proposed,and the corresponding grinding conditions under this structure were simulated,and grinding experiments were carried out to indirectly verify the reliability of the numerical simulation.Comparing the grinding data of ungrooved grinding wheel and grooved grinding wheel,the grinding wheel performance was evaluated from many aspects.The results show that the average surface roughness of the silicon rod after grinding with slotted wheel is 0.095μm,which is about 10% lower than that with unslotted wheel.In the grinding process,the average maximum current value is 9.5A,which is reduced by about 21%.The average repair interval is 18700 mm,increased by 38%;There is no obvious blackening phenomenon on the surface of slotted grinding wheel.The frequency and power/frequency ratio of acoustic signals during grinding are also significantly lower than those of ungrooved grinding wheels.The experiments show that the slotting design of the grinding wheel block to some extent weakens the blocking effect of the air barrier layer on the grinding fluid,increase the volume distribution of grinding fluid in the grinding area,improve the cooling and cleaning effect of grinding fluid,and increase the self-sharpness and service life of grinding wheel,so as to improve the grinding quality and grinding efficiency of grinding wheel.Put forward guiding suggestions for actual production and processing.