| Ratooning rice is a rice planting mode that promotes the dormant buds on the rice pile to sprout and grow into ears after the first harvest through certain cultivation and management measures,so as to harvest another season of rice.It has the characteristics of low production cost,good rice quality and high yield potential.At present,the top dressing of bud promoting fertilizer in Ratooning season of ratooning rice is mainly manual application,which has high labor intensity,low operation efficiency and very high labor cost.In recent years,with the continuous increase of labor cost,the demand for mechanized Topdressing of bud promoting fertilizer for ratooning rice is becoming stronger and stronger.Therefore,combined with the agronomic characteristics of Ratooning Rice in the middle and lower reaches of the Yangtze River,this study developed a pneumatic ratooning rice bud promoting topdressing machine,which uses a two-stage fertilizer ejector to discharge fertilizer.The device combines the advantages of grooved wheel fertilizer ejector and toothed fertilizer ejector,and combined with the deflector gas separator with good gas separation performance,which can not only increase the width of fertilization and improve the operation efficiency,but also accurately control the amount of fertilizer discharged,Effectively improve the continuity and uniformity of fertilization and meet the topdressing requirements of bud promoting fertilizer for ratooning rice.The main research contents are as follows:(1)Complete the determination of granular material characteristics of bud promoting fertilizer.Taking urea granular fertilizer as the test sample,the basic physical characteristics were measured.The measured particle sphericity was 0.92,the particle length,width and height size range was mainly 2～3.5mm,the equivalent diameter was 2.95mm,the real particle density was 1.86g/mm~3,and the bulk density was 0.962g/mm~3;The mechanical properties of fertilizer particles were measured.The friction coefficient between sample particles and ABS plastic material was 0.43,the collision recovery coefficient was 0.513,the sliding angle with 304 stainless steel material was 23.5°,the friction coefficient was0.51 and the collision recovery coefficient was 0.432.The test results can provide an important reference for the structural design and performance simulation of Ratooning Rice Bud promoting topdressing machine.(2)Complete the design of the overall structure scheme of Ratooning Rice Bud promoting topdressing machine.According to the agronomic characteristics of Ratooning Rice and the topdressing requirements of bud promoting fertilizer,the topdressing mode of bud promoting fertilizer is determined.The pneumatic topdressing machine is equipped with the ratooning rice harvester to complete the topdressing operation of bud promoting fertilizer while harvesting in the first season.The whole structure of the topdressing machine mainly includes fertilizer box,frame,gas separation device,governor,two-stage fertilizer ejector,fertilizer guide pipe,fertilizer discharge nozzle and other components.(3)A two-stage fertilizer ejector is designed.Considering that the application amount of bud promoting fertilizer for ratooning rice is relatively small and the requirements for the continuity and uniformity of fertilizer discharge are relatively high,a two-stage fertilizer discharge device is designed in this study,and its key structural parameters are determined.Among them,the radius of groove wheel is 34.5mm,the pitch of groove hole is 13mm,the effective depth of groove hole is 8mm,the width of groove hole section is 9.5mm,the width of groove hole section is 6.5mm,and the radius of tooth top circle of tooth fertilizer discharge gear is 33.5mm,The center distance of two tooth fertilizer discharging wheels is60mm.Through the theoretical calculation and discrete element simulation analysis of the fertilizer discharge amount and process of the upper and lower fertilizer discharge devices,it is found that the optimal transmission ratio of the rotating speed of the grooved wheel and the toothed fertilizer discharge wheel of the two-stage fertilizer discharge device is1:1.8;In the rotating speed range of 10～20r/min,the fertilizer discharge amount of the fertilizer ejector is linearly correlated with the rotating speed,and the consistency variation coefficient of the fertilizer discharge amount at each fertilizer discharge port is the largest,which is 2.57%.(4)A deflector gas separation device is designed,and the gas separation performance of the gas separation device is simulated.It is found that the opening angle of the deflector has an important impact on the gas separation performance of the gas separation device.With the increase of the opening angle of the deflector,the flow velocity consistency variation coefficient of each exhaust port first decreases and then increases.When the opening angle is 48°,the flow velocity consistency variation coefficient of each exhaust port is the smallest,which is 5.65%.At this time,the average wind speed of each exhaust port is 19.37m/s,which meets the design requirements of pneumatic fertilizer transportation.(5)Complete the structural improvement and performance optimization of the air fertilizer mixing device.The vertical connection between the feed pipe and the gas pipe of the raw gas fertilizer mixing device is changed to an inclined connection at a certain angle,and part of the feed pipe is extended into the gas pipe to improve the flow rate and prevent the air flow from blowing up along the feed pipe.Through the fluid simulation test,the internal air flow movement law of the two kinds of air fertilizer mixing devices before and after optimization is observed.The results show that the flow rate improvement effect of the optimized air fertilizer mixing device is significantly higher than that before optimization,and there is no upward blowing phenomenon;Through cfd-dem fluid structure coupling simulation test,the speed-up effect of the two kinds of gas fertilizer mixing devices on particles before and after optimization is analyzed.The results show that the speed-up effect of the optimized device on particles is 93.6%higher than that of the original structure,indicating that the optimization scheme of the mixing device is effective.(6)The performance bench test of Ratooning Rice Bud promoting and topdressing machine was completed.The wind speed at each exhaust port of the gas separation device of the topdressing machine and the fertilizer discharge port at the fertilizer discharge nozzle is measured.The results show that the minimum velocity at the exhaust port is 18m/s,the velocity at each exhaust port is consistent,and the coefficient of variation is 6.02%,which is only 0.37%different from the simulation test results;The minimum wind speed at the fertilizer outlet is 15.2m/s,which can meet the flow rate requirements of the pneumatic fertilizer conveying system of the topdressing machine.According to the design scheme,the trial production of Ratooning Rice Bud promoting and topdressing machine is processed and installed on the double motor crawler chassis platform for the bench test of fertilizer discharge performance.The test results show that within the speed range of 10～20r/min,the maximum variation coefficient of consistency of fertilizer discharge in each row is3.09%,and the maximum variation coefficient of fertilizer discharge uniformity is 27.01%,which meets the requirements of variation coefficient in NY/T1003-2006 technical specification for quality evaluation of fertilization machinery.In addition,by analyzing the data of displacement consistency test and fertilizer discharge uniformity test,it is found that when the rotating speed is 15r/min,the variation coefficient of fertilizer discharge consistency and fertilizer discharge uniformity of each row are the smallest,indicating that the device has the best performance when the rotating speed is 15r/min. |
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