Design And Experiment Of An Automatic Sewage Discharge System Based On The Freshwater Fish Captive Mode

Pond aquaculture is an important way of freshwater aquaculture in China.However,the lack of efficient mechanized equipment in the sewage discharge process has been a major challenge.Currently,the sewage discharge link is mainly operated manually,resulting in low efficiency,poor solid waste removal effect,high labor intensity,and difficulty in accurately controlling sewage discharge.These limitations have significantly hindered the further development of the aquaculture industry.To address this issue,based on the pond "zero discharge" captive mode proposed by the College of Fisheries of Huazhong Agricultural University,a tangential inflow spinning captive bucket with selfcleaning ability was designed by using computational fluid dynamics(CFD).What’s more,an automatic sewage discharge system for the pond captive mode was developed with the PLC as the core control component.It realized that the tangential inflow spinning captive bucket could use the spiral flow at the bottom of the captive bucket to remove solid particles attached to the bottom surface of the bucket.And the automatic sewage discharge system realized field,remote,and timing automatic control of the sewage discharge link in the pond captive mode.The main research content and results are as follows:1)Three types of captive buckets structures were proposed to use the swirling flow to clean the solid particles attached to the bottom surface of the captive bucket,including the guide strip spinning captive bucket,the impeller spinning captive bucket and the tangential inflow spinning captive bucket.Using CFD method,fluid dynamics simulations were conducted for all three structures.Based on the simulation results,the tangential inflow spinning captive bucket was finally selected as the design scheme.The specific structure of the tangential inflow spinning captive bucket was proposed.Applying CFD software,the three-dimensional flow model of the tangential inflow spinning captive bucket was established,and the single-phase flow simulation was conducted on it.The simulation results were used to investigate the impact of four parameters,namely the number of tangential inlets,the installation position and angle of the tangential inlets,and the velocity of water in the tangential inlets,on the tangential velocity distribution on the bottom surface of the captive bucket.Additionally,the effect of these parameters on the flow range of the high-speed flow was also analyzed.Physical models of the ordinary captive bucket and the tangential inflow spinning captive bucket had been manufactured using 3D printers.And the sewage discharge tests were carried out.Firstly,the decontamination performance of the tangential inflow spinning captive bucket had been verified.It was determined that an installation angle of 55° and a tangential inflow velocity of 0.018 m/s yield the best results for removing feed particles attached to the bottom of the captive bucket,which is consistent with the conclusions of fluid simulation analysis.Then,the optimal tangential inflow spinning bucket was selected for comparison with the ordinary bucket.It was found that the removal performance of the tangential inflow spinning bucket on the feed particles attached to the bottom surface of bucket was significantly stronger than that of the ordinary captive bucket.2)The overall scheme of the automatic sewage discharge system was then designed according to the tangential inflow spinning captive bucket.What’s more,to meet the control requirements of the automatic sewage discharge control system,various hardware components such as the PLC,touch screen,and motor operated valve were carefully selected.And the connecting circuit of the automatic sewage discharge control system was designed.The PLC control program was designed by using STEP 7-Micro WIN SMART V2.6.0.0 software.To enhance the user experience,the human-computer interaction system was designed by using MCGS Pro software and King View 6.55 software.This resulted in a more intuitive and efficient control method,allowing for precise and effective management of the automatic sewage discharge control system.3)A laboratory-scale automatic sewage discharge system had been developed and tested for its operational efficiency.The system was subjected to a series of tests to evaluate the performance of each sensor.The turbidity sensor,liquid level sensor,and p H sensor were found to be functioning normally in the test system.The human-computer interaction system was verified.The PC and touch screen could be used to monitor and control the sewage discharge system at the same time.The remote control of the automatic sewage discharge system was achieved by using a PC,King View 6.55 software,and Sunflower software.Finally,the automatic sewage discharge operation was also tested,and it was observed that the system could control the actuating members,such as solenoid valves and water pumps,to complete automatic sewage discharge according to the prepositioned sewage discharge strategy.The automatic operation of the sewage discharge system was successfully realized,and all the various functions of the automatic sewage discharge system met the design requirements.