Abstract
Injectors are key pieces of equipment for chemigation systems, and their hydraulic performance has a significant effect on chemigation systems and crops. In order to investigate the influence of different working parameters on hydraulic performance for a water-powered proportional injector (PI), three key parameters of inlet and injection flow rate were researched using a one-factor experimental design method. The regression equations between different factors and response variables were established through a response surface method based on one-factor experimental results. Lastly, a mathematical model of the actual injection ratio was established. Some experiments under different, randomly selected parameter combinations were carried out to verify the prediction precision of the mathematical mode. The results showed that the injection flow rate increased first within the differential pressure of 0.05 to 0.10 MPa and then tended towards stability with increasing differential pressure. The injection flow rate decreased by increasing the viscosity and the change in the injection flow rate was small enough when the viscosity was greater than 500 mPa·s. The impact factors, in order of significance, for inlet flow rate were differential pressure, viscosity of injection liquid and setting injection ratio. The impact factors, in order of significance, for injection flow rate were viscosity of injection liquid, setting injection ratio and differential pressure. The regressive model for predicting the actual injection ratio was validated using an experiment and the relative deviation between calculated value and tested value was less than 5.98%, which indicated that the mathematical model had high credibility.
Highlights
Chemigation is the injection of any chemical such as fertilizers, micronutrients, or pesticides into irrigation water and is applied to the land using an irrigation system
Injectors are key pieces of equipment for chemigation systems, and their hydraulic performance determines the quality of the chemigation system to a great extent [7,8,9]
Han et al [32] analyzed the injection performance of three types of proportional injectors through experimental research, and pointed out that the injection flow rate of the proportional injectors was affected by the differential pressure, the operating conditions of high pressure and large flow will affect the injection performance, the inlet flow rate should not exceed the design flow rate when the proportional injector is working, and the inlet flow rate should not be too large when the injection ratio is small
Summary
Chemigation is the injection of any chemical such as fertilizers, micronutrients, or pesticides into irrigation water and is applied to the land using an irrigation system. PIs are widely used in fertigation systems for greenhouses and cash crops [19,20] For this kind of injector, there were some studies that reported on its mechanical structure design. Li et al [24] analyzed the structure principle and main performance parameters of a fertilization pump, and carried out a hydraulic performance test, indicating that the injection ratio of the fertilization pump was relatively stable under different inlet and outlet pressure differences. Bracy [26], Tayel [27] and Li [11,15] successfully applied a PI as one kind of injector to inject fertilizer into irrigation water and indicated that the use of a PI can result in good water and fertilizer distribution uniformity because of the high injection precision of the Venturi injector.
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