Design And Experiment Of Water-fertilizer Integrated Sprinkler Irrigation System Based On Peristaltic Pump Preparing And Injecting Fertilizer

In China,the degree of land intensification is insufficient,agricultural water resources are scarce,and fertilizer utilization is low.Water-fertilizer integration technology can improve water-fertilizer utilization efficiency.However,the existing water-fertilizer integrated devices suitable for sprinkler irrigation system have the problem of low fertilization accuracy and controllability,and the fertilization performance needs to be improved.Therefore,the research about water-fertilizer integrated sprinkler irrigation system has great significance.The methods of theoretical analysis,experimental and numerical simulation were adopted,the water-fertilizer integrated sprinkler system and fertilizer injection device based on the hose reel irrigator and large flow rate peristaltic pump were studied.The main contents were as follows:(1)The water-fertilizer integrated sprinkler irrigation system was designed,and the spraying performance model of the system was established.The water-fertilizer integrated sprinkler irrigation system mainly included two parts: the fertilizer preparation and injection device,and water-fertilizer spraying device.The fertilizer preparation and injection device used the positive and negative characteristics of peristaltic pump to complete the fixed proportion of fertilizer preparation and injection,and the water-fertilizer spraying device used the hose reel irrigator to complete the spraying of water-fertilizer.The hydraulic performance evaluation indicators of the water-fertilizer integrated sprinkler irrigation system were elaborated,which mainly include sprinkler irrigation intensity,spraying uniformity,spraying variation coefficient,equipment hydraulic loss,fertilization amount,fertilization uniformity and mixed fertilizer uniformity.The mathematical models of fertilizer preparation,fertilizer injection and spraying in water-fertilizer integrated sprinkler irrigation system were established,respectively.(2)The structure optimization of large flow rate peristaltic pump of high-precision water-fertilizer integrated spraying device.Aiming at the problem of local backflow in large flow rate peristaltic pump,in order to reduce the degree of backflow and the hydraulic loss,increase fertilizer accuracy and improve the hydraulic performance of the peristaltic pump,a peristaltic pump performance parameter model was established to optimize the structure of the key pump head roller.Different pump head structures with 2,3,and 4 rollers of the peristaltic pump were carried out to test the flow rate,pressure,pump tube temperature,and reducer temperature.The results show that the pump head structure had a great influence on the flow rate and pressure of peristaltic pump.The four-roller pump head structure slows down the high-frequency squeezing of the pump tube and reduces the flow rate of fluid.The pump flow rate accuracy and pressure were improved.Compared with the two-roller and three-roller structure,the peristaltic pump with four-roller structure increased the flow rate by 30.33% and 8.95%,respectively,the degree of backflow was reduced by 21.96% and 8.76%,the maximum pressure was increased by 0.105 and 0.035 MPa respectively,and the maximum temperature of the pump pipe increased by 13℃ and 8℃,respectively.Therefore,the four-roller structure of the peristaltic pump was a better structure.(3)Aiming at the problem that the peristaltic pump tube is prone to fatigue damage,the stress of the peristaltic pump tube under different hardness conditions were simulated numerically.The Workbench software was used to analyze the impact of hardness on the pump tube when it was working.Numerically simulate the closed state of the pump tube to obtain the stress distribution law.The hardness of the pump tube was selected as 50,55,60,65 and 70,respectively.The results show that,as the hardness increased,the stress generated by the squeezing of the pump tube increased.The maximum stress generated by the complete closure of the pump tube had an exponential relationship with the hardness of the pump tube.The maximum stress produced by the pump pipe was 3.4179,3.6433,5.0166,6.1587 and 7.6825 MPa,and the stress gradient increased by 14.92%,58.23%,94.24% and 142.34%,respectively.With the increase of hardness,the stress mutation at the place where the maximum stress occurs was more severe,and fatigue damage is likely to occur.The pump pipes with lower hardness are beneficial to reduce the stress generated by the work of the pump pipes and prolong the service life.(4)Experiments on the performance of water-fertilizer integrated sprinkler irrigation system were carried out.The spraying model and the water-fertilizer concentration model for the operation of the water-fertilizer integrated sprinkler irrigation system were established respectively,and the optimal irrigation condition of the water-fertilizer integrated sprinkler irrigation system was 70-120 kPa,and the fertilization condition was 70 kPa.The results show that,under the irrigation and spraying condition,the spraying requirements are met at 70-100 kpa pressure,the spraying uniformity was more than 75%,the spray volume model accuracy was within 9.5%,and the working condition with small hydraulic loss is 70 kPa.Under the water-fertilizer spraying conditions,the verification of water-fertilizer spray model was accurate relatively,and the accuracy of the fertilizer concentration calculation model was within 6%.It meets the requirements of integrated water-fertilizer spraying.