Design And Experiment Of Multi-Fertilizers Mixing Device By Air Blowing And Blade Stirring

In the process of crop growth,fertilizer is particularly important for the increase of yield.However,incorrect fertilization may lead to low fertilizer use efficiency,soil consolidation and agricultural non-point source pollution.At present,the mainstream variable rate fertilization machinery is to control the amount of compound fertilizer with a fixed ratio,which can not achieve the accurate proportion of nitrogen,phosphorus and potassium(N,P,K)according to soil demand,and the mixing device is large and the fertilizer is not evenly mixed.Can not be directly loaded on the field variable rate fertilization machinery for operation.In this paper,a kind of air-blowing mixing device for multi-element fertilizer is designed,the mixing uniformity of multi-element fertilizer is improved by the combination of mechanical stirring and air blowing,and the mixing parameters are optimized by EDEM-Fluent coupling simulation and bench test,so as to improve the comprehensive utilization efficiency of fertilizer.The main work of this paper were as follows:(1)By consulting the literature to analyze the current application of variable rate fertilization and discrete elements,according to the requirements of variable rate fertilization,a multielement fertilizer air-stirring and mixed variable rate fertilization device was designed.The material of mixing chamber and agitator is steel,the material of fertilizer box is acrylic,and the material of falling fertilizer pipe and ventilation pipe is PVC.The outer groove wheel fertilizer discharge device is driven by three independent motors,and the duty ratio is adjusted by PWM DC motor speed regulation encoder to realize fertilizer discharge adjustment.The air input speed is adjusted by frequency converter.(2)The air-blowing mixing device of multi-element fertilizer was designed according to the requirement of variable rate fertilization.The material of mixing chamber and agitator is steel,the material of fertilizer box is acrylic,and the material of falling fertilizer pipe and ventilation pipe is PVC.The outer groove wheel fertilizer discharge device is driven by three independent motors,and the duty cycle is adjusted by PWM DC motor speed regulation encoder to realize fertilizer discharge regulation.The air input speed is adjusted by frequency converter.(3)The structure of the agitator,which is the key part of the device,is designed:single blade group and double blade group,and simulated and analyzed by EDEM software,when the agitator speed nb is 600 r min-1,the optimal structure is determined.In the single leaf group,the blade installation angle a is 20°,and the mixing uniformity of N,P,K fertilizer particles under this condition is 90.29%,89.64%and 89.22%,respectively;in the double leaf group,the installation angle β of the upper leaf group is 20°,and the installation angle of the lower leaf group is-20°,and the spacing h is the best for 89mm.Under this condition,the mixing evenness U1(N,P,K)is 93.42%,94.89%and 92.96%,respectively.The precision of fertilizer application U2(N,P,K)is higher than 85%,indicating that the device runs stably and meets the requirements.(4)The optimal combination of agitator speed nb and air input velocity va is determined by EDEM-Fluent coupling.The airflow input speed va is 8.4 m·s-1,and the agitator speed nb is 740 r min-1.Under this condition,the simulation results show that the mixing uniformity U1(N,P,K)is 98.41%,98.12%and 98.31%,respectively.The precision of fertilizer application U2(N,P,K)is higher than 85%,indicating that the device runs stably and meets the requirements.(5)The test rig was built according to the structural design of the device to check the rationality of the device design and its operability.The mixing uniformity of single blade group U1(N,P,K)was 88.84%,88.46%and 88.41%,respectively.The fertilizer application accuracy U2(N,P,K)was 88.68%,88.94%and 87.07%,respectively;the mixing uniformity U1(N,P,K)of the two-blade group was 92.93%,93.52%and 91.89%,respectively.The fertilizer application accuracy U2(N,P,K)was 90.06%,89.77%,90.68%,respectively;the mixing uniformity U1(N,P,K)of air-blown mixing group was 97.02%,96.93%,96.31%,respectively.Fertilizer application accuracy U2(N,P,K)was 91.45%,90.72%,91.47%.The mixing uniformity error is within 2%,and the simulation model has reliability.The accuracy of fertilizer application amount were higher than 85%indicates that the machinery operation is stable and meets the condition.