Design And Experimental Study Of Up-suction Rice Mill With Annular Air Duct

Rice mill is the core equipment in rice processing technology,and its milling performance is directly related to the quality of milled rice products.According to the layout of milling roller,rice mills are mainly divided into the horizontal rice mill and the vertical rice mill.Among them,horizontal air-jetting rice mill is still the mainstream of industrial application.There is a problem in rice mills: the down air suction method often is used by the horizontal rice mills to collect the rice bran.However,due to the broken rice produced in the milling process,some smaller broken rice and rice bran are discharged from the milling chamber together and collected by the lower collecting hopper.Broken rice and rice bran have different nutritional values,and they need to be separated in production to obtain maximum profit.For this reason,the rice bran-broken rice separator is usually installed separately from the back of the rice mill to separate the broken rice from the rice bran.However,this solution has problems such as high input cost and high energy consumption.Based on aerodynamics,the air duct of the existing rice mill was improved,and an up-suction rice mill with unique annular air duct was designed,which can directly separate rice bran from broken rice by air separation inside the rice mill without adding rice bran-broken rice separation equipment at the back of the rice mill.Firstly,the overall structure of the scheme was designed,and the suspension velocity of rice bran and broken rice was tested,simulated and calculated theoretically,and the results are used as the basis for air duct design;secondly,the flow field in the rice mill under different up-suction wind speeds was simulated by using CFD simulation;thirdly,the separation process of rice bran and broken rice was simulated by using CFD-DEM coupling method;then,the physical prototype was built,and a simple PIV experimental platform based on PIVlab was built to observe the movement of particles.Finally,a physical model was proposed to calculate the movement of rice bran,and the results were compared with the experiment and simulation.The results are as follows:(1)Many experimental calibration methods were used to calibrate the physical contact parameters between different particles.Based on DEM simulation technology,the discrete element multi sphere model of rice,rice bran and broken rice particles was established by using experimental parameter,and then the suspension velocity of the particle model was measured by using CFD-DEM method,and compared with the experimental and theoretical results,it was found that the data is stable and the particle modeling is accurate.(2)The influence of up-suction wind speed on the flow field in the new rice mill was understood.Based on CFD simulation technology,the characteristics of flow field in annular air duct with different up-suction wind speed were studied.The sliding mesh model(SMM)was used to simulate the influence of rotation of milling roller,and the porous medium model was used to simulate the obstruction of particles to air flow in milling chamber.Finally,an experimental prototype model was built.The results show that the rotation of the roller had little effect on the average wind speed of the annular air duct,and the high-speed airflow from the blow hole only had a significant effect on the local flow field.When the wind speed was 6 ? 8 m/s,it was expected that the separation of rice bran and broken rice can be realized.The average wind speed in the air duct of the prototype was measured by the anemometer,and the measured data was close to the simulation.(3)The influence of up-suction wind speed on particle motion was clarified.Based on CFD-DEM,the movement characteristics of particles in the air duct under different up-suction wind speeds were simulated and analyzed.PIV experimental platform was built based on PIVlab to analyze the movement of particles in the experimental prototype.The results show that: when the up-suction wind speed was 2 ? 8 m/s,the broken rice falls from the lower air inlet;when the up-suction wind speed was 2 ? 4 m/s,more rice bran falls down,which could not achieve the separation of rice bran and broken rice;when the up-suction wind speed was 6 ? 8 m/s,the rice bran moved upward in an arc track close to the air duct wall,which can achieved the full separation of particles.Finally,a physical model for calculating rice bran movement was proposed based on MATLAB.The calculated data of the model were basically consistent with the simulation and experimental data.The results show that the new type of updraft rice mill can directly separate and collect rice bran and broken rice compared with the existing rice mills,and the established physical model can well predict the movement of particles.The above research is of positive significance to the performance improvement and process innovation of rice mill.