LAUSR

Pneumatic submersible pump is a new type of drainage tool in farmland irrigation. The water supply at the pumping end of the submersible pump is sporadic with frequent no-load operation given the low water levels in most rural canals during summer. The change in water flow and pressure directly causes high turbine speed and thus leads to the runaway speed phenomenon, which seriously affects operational safety. A pneumatic control system based on metering-out control was proposed to prevent high turbine speed and minimize the consumption of the pneumatic submersible pump in irrigation and drainage. First, the pneumatic liquid level control system was designed to automatically adjust the pressure and flow of the submersible pump under no-load and load conditions. Second, the stability of the system was simulated by Advanced Modeling and Simulation Environment for Systems Engineering (AMESim), and the coupling relationship among turbine speed, inlet pressure, and flow rate was discussed with different metering-out flows. Finally, comparative experiments were conducted for verification. Simulation and experimental results show that under the no-load condition, when the inlet pressure reaches 0.2 Mpa, the rotating speed of the pneumatic submersible pump increases with the inlet pressure, and when the inlet pressure reaches 0.4 Mpa, the rotating speed of the pneumatic submersible pump remains approximately unchanged. When the outlet flow increases, the rotating speed of the pneumatic submersible pump also increases gradually; when the outlet flow is equal to the inlet flow, the rotating speed remains stable; when the inlet pressure is higher than 0.4 Mpa and the outflow flow is smaller than 18 m/h, the turbine speed can be less than 12000 r/min, which is lower than the critical runaway speed. Thus, the total power loss is not reduced. The control system solves the problem of runaway speed and realizes automatic speed control of the pneumatic submersible pump under the no-load condition. The proposed method provides wide application prospects and is suitable for discontinuous irrigation and drainage operation of rural canals.