The siphon time regulation controller is a device which can automatically adjust the hydraulic pressure in surge valve by adjusting the inflow flow of float chamber and the drainage flow of siphon pipe to achieve intermittent siphon time drainage.
According to the characteristics of the self-made surge valve and the need of irrigation, the mathematical model is established by analyzing the periodic water supply time, the inflow flow and the drainage flow. The parameters of the siphon time control controller are determined, and the stepless regulation of the device is analyzed. The experiment proves that the design parameters meet the irrigation requirements, and the siphon time regulation controller can also be used as a reference for the design of other surge valves. Surge irrigation is a relatively new irrigation method, which uses low head flow to advance rapidly and intermittently to drain water into ditches and border [1]. Compared with continuous irrigation, it has the advantages of uniform irrigation, saving water and time, and small deep leakage.
It is considered as a major breakthrough in surface irrigation technology. However, for mechanical terraced fields in Hilly and mountainous areas, the rainwater collected by dry wells is less, and the irrigation quota is limited to a large extent. Especially in the mechanical terraced fields located on the Loess Plateau, the former surge valves are limited in production practice due to high cost and complex technology. Therefore, this study combines the characteristics of local irrigation and designs a siphon time regulation controller through mathematical model analysis. This small-scale surge irrigation equipment has the advantages of simple structure, stable performance, low price and easy operation. Its research and development can further promote the development and application of surge irrigation technology. The siphon time regulator is composed of a steady flow mechanism and a siphon mechanism. Stable flow mechanism and siphon mechanism jointly complete the time regulation of surge valve. The design of the flow stabilizing mechanism makes the flow into the float chamber constant, so that the siphon mechanism can accurately control the rise and fall of the float. The function of siphon mechanism is to realize the timing conversion of valve plates by adjusting the lift travel time of float under the constant flow provided by the steady flow mechanism. The flow stabilizing mechanism is mainly composed of water tank, float ball valve and filter tube. The float ball valve is composed of small float ball, plastic rod, rubber diaphragm with convex platform, inlet pipe and outlet pipe.
The function of the flow stabilizing mechanism is to provide constant flow for siphon mechanism (Fig.
1). The principle of flow stabilization mechanism is to open a small hole in the lower side of the water tank according to Euler method in hydraulics. If the water level in the water tank keeps constant (without changing with time), all the moving elements of the water flowing from the orifice will not change with time, that is, the water flowing from the orifice will be a constant flow [3]. The main structure of siphon mechanism is composed of float, float chamber, siphon, suction pipe, suction auxiliary pipe, siphon destroying pipe and drainage device. Its working principle is to take the air from the siphon pipeline by using the fast flowing water in the suction pipe, so that a certain degree of vacuum is formed in the siphon pipeline. Under the action of the atmospheric pressure difference inside and outside the pipeline, the water in the float chamber enters the siphon pipeline and discharges into the drain. The flow rate in the siphon can be adjusted by the valve disc, which can automatically stop the drainage within a specified time, as shown in Figure 1. The siphon mechanism parameters are determined according to the two parameters of design drainage flow and drainage cycle. The drainage period is composed of water intake stage, air pumping stage and siphon drainage stage.
The intake stage is the time required for float to rise from the bottom of the float chamber to start pumping from the exhaust pipe; the suction stage is the time from the beginning of pumping to the end of pumping; and the siphon drainage stage is the time for float to descend from the highest position to the lowest position. Influent time. In the stage of water supply, find out the relationship between the inflow of floater chamber and t1, t2, and the relationship between the inflow of floater chamber and the drainage of siphon and T3 in the stage of water shutdown. Establish the mathematical model between the period of water supply or the period of water shutdown, the inflow of floater chamber and the drainage flow of siphon, so as to realize the regulation of the inflow of floater chamber and the drainage flow of siphon. Stepless regulation of periodic water supply time and periodic water shutdown time is realized in the perimeter. In the formula: T-periodic water supply time or periodic water shutdown time, s; Q-siphon-t3 time siphon drainage average flow, thermostatic element m3.s-1; Q-float chamber inflow, m3.s-1. Professor Gao Changzhen of Engineering and Technology College of Shanxi Agricultural University and other experts analyzed the characteristics of rainwater harvesting irrigation in dry wells in Hilly and mountainous areas, and the results of surge irrigation experiments on short furrows and small-scale irrigation plots in Hilly and mountainous areas [5] showed that the irrigation period of Surge Irrigation on small-scale plots in Hilly and mountainous areas generally ranged from 15 to 45 minutes. Based on this, the irrigation period ranged from 15 to 45 minutes.
The mathematical model between the periodic water supply time or the periodic water shutdown time, the inflow Q of the float chamber and the drainage Q-rainbow of the siphon is established.
The optimal combination of the Q-rainbow and the Q-rainbow can achieve the accuracy of the periodic water supply time and the periodic water shutdown time, and the high sensitivity of the surge irrigation equipment is realized. From (22) it can be seen that the siphon drainage flow has a linear relationship with the inflow of the float chamber within a certain period of water supply or the period of water shutdown.
The siphon drainage flow varies with the inflow of the float chamber. In each application of surge equipment, the periodic water supply time or the periodic water shutdown time is determined, and the siphon drainage flow has a unique value corresponding to the inflow of the float chamber with a certain value. That is to say, by adjusting the inflow of the flow stabilizing mechanism into the float chamber and adjusting the drainage flow of the siphon according to the mathematical model established by formula (22), the stepless regulation of the periodic water supply time or the periodic water shutdown time can be realized between them. The device has the advantages of simple structure, stable performance, great cost savings and easy popularization.
The whole set of devices can operate without external power, which is easy to operate and more energy-saving and environmental protection. It can realize stepless adjustment of surge irrigation parameters and has higher sensitivity. The siphon time regulation controller designed in this experiment has the advantages of simple structure, low cost, economy and energy saving. However, this result is based on the analysis of mathematical model test, and its performance needs to be further proved and improved in the experiment.