Design And Experiment Of Variable Rate Fertilization Control Device For Venturi Injector

Water and fertilizer were important factors to affect crop growth.At present,the utilization ratio of water and fertilizer was relatively low in agricultural production in China,which not only increased production cost input,but also lead to water and fertilizer waste.It also caused pollution to agricultural soil and water environment.Fertilizer integration technology was one of the effective ways to solve the problem.Fertilization device was an important part of water and fertilizer integrated system,while the Venturi injector had the advantages of simple structure,economical and practical advantages as a common fertigation device used widely in our country.At present,the research on the Venturi injector had been developed,but in the practical application,it was difficult to realize the automatic and continuous adjustment of the concentration of fertilizer and the excessive loss of the device during the adjustment process.In this paper,a variable fertilization control device based on Venturi injector was designed to solve the problem that the cost of fertilizer application was high,the concentration of fertilizer was difficult to be adjusted continuously and the loss of the device was too large.The main contents of the research were as follows:(1)The structure parameters of the throat was optimized further using CFD method in this paper.A set of structural parameters was set up to meet the low pressure irrigation system.It was made into a sample by 3D printing technology.The CFD method was verified by experimental measurement.And the results showed that when the inlet pressure of the Venturi injector was0.05 MPa,the maximum concentration of the fertilizer was 9.3%,which can met the demand of actual irrigation.(2)Based on the optimized Venturi injector above,a variable rate fertilization control device was designed at the sucking mouth.The device was mainly composed of needle type valve,DC motor and control main board and so on.The needle valve was installed between the sucking pipe and the sucking mouth,and the needle valve was controlled through the direct current motor.Through the test,it was proved that the device could realize the continuous adjustment of the concentration from 0 to the maximum.In order to effectively shorten the reaction time of the device,the speed of the DC motor was adjusted by the variable speed.The relationship between the motor voltage and the speed of the motor was a line,which is R~2>0.99 by the test.(3)On the basis of the hardware structure of the variable rate fertilization control device of Venturi injector,the control circuit was designed.And the fuzzy control method was used to realize the on-line control of the concentration of fertilizer.Through a large number of experiments,it was proved that the device could realize the continuous adjustment of the concentration of the fertilizer,and the maximum error of the concentration of the fertilizer was0.2%,and the response time of the device was between 5.3~8.4 s.The errors and the response time could meet the demand of the actual irrigation.The safety test had been done to verify it.The results showed that the device had a safety performance of 100%.In summary,by optimizing the structural parameters of the Venturi injector and based on the optimized Venturi injector used CFD technology,a variable rate fertilization control device was designed.Through the test and analysis of the whole control device,the on-line rapid and continuous adjustment of the concentration of the fertilizer was realized.And the actuator was controlled by needle valve,and it was reduced the loss of the fertilizing device effectively.In actual irrigation system,the variable control device of Venturi injector could carry out variable fertilizer application according to the actual requirement of water requirement of the crop.It could not only supplement the theory and method of Venturi injector for variable fertilization,but also effectively solved the problem of fixed fertilization concentration and the influence of water pressure on the water pressure.It also widened the application scope of the fertilizer applicator and opened up a new way for the fine management of water and fertilizer irrigation.It had important theoretical value and practical significance for precision agriculture and high efficiency fertilization.