| At present,artificial fertilization is still the main fertilizer application method in rice production in China.This method is extensive,the fertilizer application amount is large but with low utilization rate,which not only wastes resources,increases production costs,but also pollutes the environment.Therefore,it is of great significance for rice production to develop advanced fertilization technology and equipment,and improve the fertilizer utilization rate.Deep fertilization in paddy field can effectively reduce the volatilization and loss of fertilizer.The technology has the characteristics of high fertilizer utilization rate,economy and environmental protection.It is the inevitable development direction of paddy field fertilization in the future.According to the agronomic requirements of deep fertilization in paddy field,based on the analysis of the current situation and characteristics of deep fertilization device in paddy field in the world,this thesis designed a kind of centralized pneumatic deep precision fertilizer applicator for rice transplanter,and researched its working mechanism.The main research contents and conclusions of this thesis are as follows:（1）The overall scheme design of a concentrated air distribution and deep fertilizer applicator for rice transplanting was put forward.According to the agronomic requirements of paddy field precision and deep fertilization,a paddy field deep precision fertilizer applicator was designed,which was consisted of screw fertilizer distribution system,centralized pneumatic fertilizer transporting system,furrow opener system,and fertilization rate control system.Screw fertilizer distributor was driven by motor to discharge fertilizer,pneumatic method was used to transport fertilizer,and the rotation speed of fertilizer discharger shaft was synchronized with that of power taken-off（PTO）to adjust the fertilization rate.The overall structures and their parameters of the above mechanical parts were designed.Through theoretical analysis,it was determined that the fertilizer amount per lap of the screw fertilizer distributor should not be less than 21 g/r,the airflow rate was 291.60 m3/h,the air speed for fertilizer transporting was 16.65 m/s,the diameter of fertilizer pipe was 32 mm,and the total air pressure of the fun should be more than 450 Pa,etc.This research provides a theoretical basis for the design of key components of paddy field deep fertilization device,such as fertilizer distributor and pneumatic fertilizer transporting system.（2）A new type of spiral fertilizer distributor with buffer zone and blocking wheel was designed.In order to solve the problem that the amount of spiral fertilizer distributor can be only adjusted by rotating speed and its fertilization uniformity is poor at low rotation speed,a blocking wheel type spiral fertilizer distributor was designed.The influence of structure and working parameters such as screw inner diameter,pitch,distance of outlet（short for length of buffer zone between fertilizer outlet and spiral end）,number of screw heads,blocking wheel opening width,rotation speed on the fertilizer amount per lap and fertilization uniformity was theoretically studied.Single factor tests based on the DEM was carried out to optimize the structural parameters of the spiral fertilizer distributor with the variation coefficient of fertilizer uniformity as the main evaluation index.L9（34）orthogonal test was carried out to study the influence of blocking wheel opening width,pitch,distance of outlet on the fertilization uniformity.The results of single factor tests showed that the fertilizer amount per lap increased with the increase of pitch and blocking wheel opening width and decreased with the increase of screw inner diameter and number of screw heads,but was not significantly affected by the distance of outlet and rotation speed of fertilizer discharging shaft.The variation coefficient of fertilization uniformity decreased with the increase of pitch,distance of outlet,blocking wheel opening width,rotation speed,increased with the increase of screw heads’number,and was not significantly affected by screw inner diameter.The results of orthogonal test show that when the screw inner diameter was set to 17 mm and the rotation speed was 20 r/min,factors affecting fertilization uniformity,from importance to secondary,mainly included distance of outlet,pitch and blocking wheel opening width.And pitch and distance of outlet had significant influence on fertilization uniformity.The simulation test results showed that the best structure parameter of blocking wheel type spiral fertilizer distributor was that the inner diameter was 17mm,pitch was 45mm and distance of outlet was 40mm.Bench tests were carried out to comparing the results of simulation tests with bench tests under the same conditions.It showed that the changing trend of the variation coefficient of fertilization uniformity of them was the same,and values were almost the same.It proved that the parameters obtained by simulation tests was correct.At the same time,the working performance of the fertilizer distributor was tested.The results showed that when the blocking wheel opening width was 10～30 mm and the rotation speed of fertilizer distributing shaft was 20～40 r/min,the fertilizer amount per lap could be adjusted in the range of 27.74～38.15 g/r,the regulating effect of blocking wheel opening width on fertilizer amount per lap was obvious;the maximum variation coefficient of fertilization uniformity was 30.03%,and the maximum variation coefficient of fertilization stability was2.18%,which met the requirements of the industry standard“NY/T 1003-2006”.This research provides a useful reference for the optimization of the structure and working parameters of the screw fertilizer distributor,and benefit to the research of precision fertilization technology.（3）Centralized pneumatic fertilizer transporting system was designed.To improve the airflow distribution consistency of each branch in the pneumatic fertilizer transportation system,so as to reduce the influence of airflow instability on the uniformity and stability of fertilizer transportation,as well as the energy waste in the process of pneumatic fertilizer transportation,a centralized pneumatic fertilizer transportation system for deep fertilization device in paddy field is designed in this paper.Through theoretical calculation,the needed air flow rate,airflow speed and fertilizer pipe diameter of the system were obtained,and the fan was selected.Based on the Fluent simulation and bench tests,the influence of three air distribution method of placing fan at the end of main duct,placing fan in the middle of main duct and centralized air distribution on the airflow velocity and consistency of each branch was analyzed.The results showed that the air flow consistency of each branch in the centralized air distribution method is the best.Taking the air velocity at the outlet of each branch and its variation coefficient as the evaluation index,single factor and L27(313)orthogonal simulation tests was carried out to optimize the structural parameters of centralized air distribution device.The simulation results showed that the primary and secondary factors affecting the air distribution consistency are sidewall inclination angle,branch diameter,branch distance,interaction between sidewall inclination angle and branch diameter,interaction between branch diameter and branch distance,and interaction between sidewall inclination angle and branch distance.The results also show that all the factors and their interactions had significant effects.The best parameter combination is sidewall inclination angle 15°,branch diameter 32 mm,branch distance 43 mm.Under the condition of best parameters combination,the variation coefficient of airflow velocity consistency of each branch is 0.27%in simulation test and1.23%in bench test,which are basically equal.Then,the air distribution performance of the centralized pneumatic transporting system was tested.The results showed that the coefficient of variation of airflow velocity consistency of each branch is 1.93%.This research optimized the structure and parameters of pneumatic fertilizer transporting system,and provided references for the design and optimization of pneumatic fertilization and seeding device.（4）A fertilization control system based on dynamic sleep vibration elimination mechanism was designed.Through theoretical analysis,a precise control system of fertilizer amount was designed,which used photoelectric sensor to measure the rotation speed of fertilizer discharging shaft and PTO synchronously,and PID closed-loop feedback algorithm was used to realize the real-time and accurate matching between the rotation speed of fertilizer discharging shaft and forward speed.The hardware selection and circuit design of the power supply,signal acquisition module,main control module,DC motor drive module and human-computer interaction module of the fertilization control system were carried out.The mathematical model of the rotation speed of the fertilizer discharge shaft,the fertilization amount and the rotation speed of the PTO was established,and a dynamic sleeping vibration elimination mechanism was proposed.Then the control system software was designed based on the mathematical model and vibration elimination mechanism.And the time coefficient of dormancy vibration elimination should be in the range of 0.3～0.4.This research could effectively improve the controlling accuracy of fertilizer amount,and provided a reference for the design of precision control system of fertilizing and seeding machines.（5）The bench performance test and field production test were carried out.In the bench tests,the rotational speeds of the fertilizer shaft were set as 10,20,30,and 40 r/min.The maximum coefficient of variation of the fertilization consistency in different rows was 1.49%at the rotational speed of 20 r/min.The maximum coefficient of variation of the fertilizer stability was 2.86%at the rotational speed of 40 r/min,while the average fertilizer amount per lap for each distributor was 26.25 g/r.The results of the dynamic fertilization tests show that the maximum relative error of the fertilizer distribution amount was 2.00%when the target fertilizer rates were 300,450,and 600 kg/hm2.The field production experiment was carried out in different plots.The plot area of300 kg/hm2 target fertilizer was 604.8 m2,the plot area of 450 kg/hm2 target fertilizer was4054.4 m2,the two plots adopted wide and narrow row（240 mm+360 mm）side deep application method,and the sum of theoretical fertilizer amount of the two plots was 200.49kg,the actual fertilizer amount was 207.57 kg,the total relative error of the fertilization amount was 3.53%,which satisfies the design standard.The results showed that compared with the 450 kg/hm2 plot of artificial fertilization with the same management in the adjacent field,when the rice yield per unit area was the same,the fertilizer could be saved about15%～20%by machine transplanting with deep precision fertilization,and the yield of rice could be increased about 5%～8%when the fertilization amount was the same.The technology of simultaneous deep fertilizing with transplanting can improve the utilization rate of fertilizer,which save cost and increase efficiency. |
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