The Material-returning Pipe Optimization Of A New Type Hammer Mill

This dissertation aims at studying on the experiment of a new hammer mill shows, the negative pressure in material-returning pipe is one of the main factors affecting its sieving efficiency. Through the3-D numerical simulation of computer and experimental testing, the relationship between the negative pressure in material-returning pipe and the sieving efficiency of the new hammer mill were studied, to provide a theoretical basis for optimal design of material-returning pipe of a new hammer mill.(1)The3-D air flows in the sieving set-up and material-returning pipe at different negative pressure were simulated and analyzed using CFD software FLEUNT14.0, the change of airflow velocity and pressure about the air field were obtained. Simulation results show that the negative pressure at outlet of the material-returning pipe had a great influence on airflow velocity and pressure in the sieving set-up. With the increase of negative pressure at outlet of material-returning pipe, the airflow velocity in the air field will increase. When the negative pressure at outlet of the material-returning pipe increases to a certain extent, the airflow velocity in the air field will decreases with the increase of negative pressure.(2)The air-material two phase flow in the sieving set-up and material-returning pipe was simulated by the Euler Model in software FLUENT14.0.Obtain the distribution of material concentration in the sieving set-up and material-returning pipe at different negative pressure. The results show that negative pressure had a greater influence on the separation of materials, when the negative pressure in material-returning is too big or to small, all can cause material deposition increases, sieving efficiency declines，and material accumulation at outside wall of pipe wall is seriously detrimental to material separation.(3)The data obtained from simulation was curve-fitting by using software MATLAB. Obtain the function relation between the negative pressure of material-returning pipe and the rate of sieving set-up. The solution can be seen, when the negative pressure in material-returning pipe is596.5Pa, the new hammer mill has the highest sieving efficiency. Provide theory basis for the optimization design of new hammer mill.(4) Testing the data obtained by simulation results show when the negative pressure near-596in material-returning pipe, the rate of sieving set-up is maximum. At the same time through the test got the size of negative pressure in material-returning pipe at different diameter. Obtain the diameter size of material-returning pipe when the negative pressure in material-returning pipe is-596Pa by cure-fitting and solution by MATLAB.