Flow Field Analysis And Performance Experimental Study On Hammer Feed Mill

During the work of hammer feed mill,the flow field of the crushing chamber will form a gas-solid circulation layer,which directly affects the performance of the mill.The sieve is an important part of the crushing chamber,and the pre-research showed that reasonable sieve shape could improve the flow field characteristics of the crushing chamber.The airfoil-triangle combined sieve with different shape parameters were designed for CPS-420 hammer feed mill,and the force of material particles in crushing chamber was obtained by using the theoretical analysis.The flow field characteristics of crushing chamber with different airfoil-triangle combined sieve were obtained by the numerical simulation.On this basis,according to the relevant national standards,the performance test study of hammer mill with different sieves was carried out.1.According to the theory of kinematics and collision in theoretical mechanics,the forces acting on materials in crushing chamber during the process of hammer impact,radial sliding along hammer and collision with sieve were analyzed.2.The internal flow field of the mill with different airfoil-triangle combined sieve were simulated by using the Mixture multiphase flow model of Fluent software,and obtained the flow field characteristics.Through the simulation analysis,it was found that the velocity and pressure distributions of the flow field inside the crushing chamber tends to be scattered and disordered when the mill equipped with airfoil-triangle combined sieve.There were many velocity and pressure gradient layers with different shapes,irregularities and sizes,which could easily cause turbulence and flutter of flow field.Then the impact crushing of hammer on materials was affected.In addition,the vortex layer with low central pressure was formed in the sieve airfoil arc and the equilateral area.The high-speed flow field was generated in the local area near the airfoil arc,which easily changed the flow field of the gap between the hammer and the sieve,and had a greater impact on material screening and crushing.3.According to the simulation results of the flow field with different shape parameters sieves,the relationship between the shape parameters of the sieve and the flow field distribution of the crushing chamber was analyzed.It was found that the airfoil arc curvature,attack angle and equal division number of sieve obviously affected the disorder and dispersion of the flow field distribution in the crushing chamber,the scales diversification of the velocity and pressure gradient layer,and the sieve of the flow field characteristic value.The primary and secondary sequence of influence of each parameter was division number,attack angle,airfoil arc curvature.4.Using yellow corn as crushing object,the crushing performance of mill with different sieves was tested.The test results showed that the mill had the batter crushing performance when the airfoil arc curvature was 0.15,airfoil arc attack angle was 15°,the equal division number was 4,and the equilateral angle was 120°.The productivity and electrical power output per kW·h of the mill were increased by 17.4%and 14.6%than the annular flat screen.5.The numerical simulation and experimental results showed that the sieve shape parameters affected the flow field characteristics of the crushing chamber and the mill performance.Reasonable sieve shape parameters were conducive to the formation of a ideal flow field to improve the mill performance.When the airfoil arc curvature was 0.15,the airfoil arc attack angle 15°,and the equal division number is 4,the optimum combination was obtained.This study provides a theoretical basis for the design of new sieve of hammer feed mill,and also provides a methodological basis for the study of flow field of rotating agricultural equipment.