| Aiming at the problems of high energy consumption,low efficiency,and over-crushing of the existing hammer-type straw feed pulverizer,in order to improve the working performance of the hammer-type straw feed pulverizer and explore the high-efficiency and low-energy crushing mechanism,the crushing form and movement process of corn straw feed were explored by theoretical analysis and high-speed photography.The one-factor experiment on corn straw crushing performance was carried out with the yield and crushing qualification rate as the evaluation indexes.A discrete element model of corn stalk including stalk nodes and suitable for computer numerical simulation of the crushing process was established.The CFD-DEM gas-solid coupling method was used to simulate the corn straw crushing process.Combined with the one-factor experiment results,the optimal range of numerical simulation results of the corn straw crushing process was obtained.The optimal working combination parameters of hammer-type straw feed grinder were obtained by orthogonal test,and the accuracy of CFD-DEM gas-solid coupling numerical simulation of the corn straw crushing process was verified.The specific research contents and results are as follows:1.In order to explore the key factors affecting the crushing effect of corn straw feed,the force analysis and motion analysis of the crushing process of corn straw feed were carried out,and the mechanical model and motion model were established respectively.2.In order to optimize the discrete element numerical simulation model of corn straw,the straw stalk section was added on the basis of the research group,and the physical experiment and EDEM discrete element numerical simulation were combined to calibrate the contact physical parameters of corn straw stalk section with the numerical simulation angle of repose as the target value,and the physical measurement test of the angle of repose was used to verify,and the relevant numerical simulation parameters of corn straw stalk section were determined : the collision recovery coefficient,static friction coefficient and rolling friction coefficient of straw stalk section-straw sheath were 0.464,0.415 and 0.356,respectively;the collision recovery coefficient,static friction coefficient and rolling friction coefficient of straw stem node-straw stem node were 0.453,0.651 and 0.411,respectively.The collision recovery coefficient,static friction coefficient and rolling friction coefficient of straw stem node-straw pulp were0.379,0.701 and 0.293,respectively.The collision recovery coefficient,static friction coefficient and rolling friction coefficient of straw stem-steel were 0.512,0.602 and0.228,respectively.3.The one-factor experiment of corn straw crushing performance was carried out with spindle speed,hammer and sieve gap and sieve diameter as test factors,and the power output and crushing pass rate as evaluation indexes.According to the test results,the CFD-DEM gas-solid coupling method was used to simulate the crushing process of corn straw under different working combination parameters of the pulverizer.The flow field velocity and pressure,the number of broken bonds,the energy loss of hammer parts and the total collision force of corn straw in the crushing chamber under different spindle speeds were analyzed.The optimal range of numerical simulation results was obtained,that is,the energy loss of hammer parts was 985.6～1312.2 J,and the total collision force of corn straw was greater than 47032.5 N.4.Combined with the one-factor experiment results of corn straw crushing performance,the three-factor three-level orthogonal test was carried out to analyze the influence of interaction between various factors on the evaluation index.The optimal combination of working parameters for the performance of the hammer-type straw feed pulverizer was obtained as follows: spindle speed 2625 r/min,hammer-screen gap 14 mm and sieve diameter 8 mm.The test results of this parameter combination are as follows:the power output is 36.85 kg/(k W·h),and the qualified rate of crushing is 76.56%.The numerical simulation verification test was carried out by using the optimal working combination parameters.The results show that the energy loss of the hammer part is1189.5 J,and the total collision force of corn straw is 49523.5 N,which are within the optimal range.The reliability of the CFD-DEM gas-solid coupling method to simulate corn straw crushing is verified.The results of this study can provide a theoretical basis for improving the key components and crushing performance of the hammer-type straw feed grinder,and provide a theoretical reference for the research of gas-solid two-phase flow in the field of agricultural machinery. |
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