Study On Temperature Rise Mechanism And Temperature Control Of Grinding Roller Based On Thermodynamics And Dynamics

When the roller mill is used to produce flour,the surface temperature of the roller will rise.If the temperature of the roller is too high,the nutrition and taste of the flour will be affected,and the wear of the roller will be aggravated.Because the flour contains water,the high temperature will make it paste on the roller surface,which will affect the grinding effect of the roller.Too high roller temperature also represents the decline of power utilization rate,the increase of power consumption,the increase of flour production cost,the waste of resources and the violation of national energy conservation and emission reduction initiatives.In view of the above problems,this paper studied the temperature rising mechanism of roller mill,determined the heat source,established the mathematical model of wheat grinding power and friction heat generation of roller in flour processing,analyzed the heat transfer of roller and verified the correctness of heat generation model through experiments,and finally put forward three temperature control measures.The lowering of the grinding roller temperature can effectively improve the flour quality and reduce the power consumption.The main research and conclusions are as follows:1.After analysis,determined the heat source of the temperature rise of the grinding roller.One is the heat released by the crushing of the wheat;the second is the heat generated by the friction of the wheat;the third is the heat generated by the friction of the bearings on the fast and slow rollers and the friction between belt of the roller's two ends and the wheels generates heat.2.Based on thermodynamics and kinetics,a quantitative study on the grinding power of the roller mill to the wheat,the total friction between the wheat and the grinding roller and the frictional heat generation was carried out,and the results showed that:the grinding power of the grinding roller to the wheat Affected by grinding roll speed,roll length,grinding roll radius,rolling distance,starting angle,and average elastic modulus.When the other quantities remain unchanged,the grinding power of the grinding roller to the wheat decreases with the decrease of the rotation speed of the grinding roller,the decrease of the length of the roller,the increase of the rolling distance,the decrease of the average elastic modulus,and the decrease of the radius of the grinding roller.The force analysis of the grinding roller was carried out,and the mathematical model of bearing heat generation was established by the whole method.3.Based on the basic theory of heat transfer,it was concluded that the heat conduction resistance of the 1M1 pulverizer's fast roll was4.476×10^-3K/W,and the surface flow heat transfer coefficient of the grinding roll was15.077W/(m²·°C),the radiant heat flow was 239.9W;the heat transfer coefficient of the left bearing seat was3.850W/(m²·°C);the heat transfer coefficient of the right bearing seat was3.901W/(m²·°C);the left part of the journal was changed The heat coefficient was5.265W/(m²·°C);the heat transfer coefficient of the right part of the journal was4.531W/(m²·°C);the heat transfer coefficient of the left gear was2.912W/(m²·°C);the right belt was shifted The thermal coefficient was3.043W/(m²·°C).4.Through ANSYS19.2 simulation analysis,the temperature rise curves of different parts of the grinding roller was obtained.The steady-state temperature of the grinding roller surface was 63.191°C,which was not much different from the actual situation.And the simulation results show that almost all the heat of temperature rise of the 1M₁ fast roller of the roller mill comes from the friction heat between the fast roller and the wheat.5.After the test,the temperature of the fast roller of the 1M₁ mill was 60°C in the steady state,and the temperature of the up grinding material and the down grinding material was 10°C and 23°C,respectively.The average elastic modulus of flour was0.38925×10⁶ Pa,the moisture content of wheat was 15.90%,and the bulk density of1M1 milled product was0.6730g/cm³.According to the calculation of the test results,the frictional heat generation power of the fast roller was 718.46W,the crushing power was 5768W,and the maximum heat generation power of the grinding roller bearing was 229.660W.It was calculated to be similar to the power consumption of 1M₁pulverizer.6.Based on the mathematical model of wheat grinding power and wheat frictional heat generation power,three temperature control measures was proposed:(1)Reduce the radius of the roller mill roller;(2)Appropriately reduce the equivalent friction coefficient between the mill roller and the wheat;(3)Reduce the average elastic modulus of wheat.