| Non-full pipe flow monitoring is essential in the field of energy measurement and pipeline transportation,and is widely used in urban pipe network monitoring,agricultural and forestry irrigation,sewage discharge and waste liquid treatment,and other scenarios.In a comprehensive analysis of commercial flow sensors,there are problems such as high cost,complex installation,poor anti-interference ability,and most of the sensors need an external power supply,maintenance difficulties,wiring complexity,and can not meet the needs of distributed sensing.The triboelectric nanogenerators(TENGs)have the advantages of low cost,strong anti-interference ability,and no external power supply.Thus,this paper proposes a method for monitoring non-full pipe flow in large pipes based on the triboelectric principle and develops a triboelectric non-full pipe flow sensor.The main research contents are as follows:Firstly,based on the theory of TENG,this paper takes the independent layer mode TENG as the basic theoretical model and elaborates the laws of charge transfer through an in-depth study of the working principle of TENG.The flow monitoring mechanism of the triboelectric non-full pipe flow sensor is analyzed by combining fluid dynamics theory,and the relationship expression between flow and the influence of liquid level and flow velocity was derived.A split multi-sensing unit design method is used to monitor both liquid level and flow velocity.Among them,the liquid level sensing unit is designed with an output-stabilized variable-area forked-finger electrodes based on the liquid-solid contact initiation principle;while for flow velocity monitoring,the design scheme of flexible blades slide toward electrodes is adopted.The working mechanism of the liquid level and flow velocity sensing units are analyzed separately to clarify the working principle and provide a theoretical basis for the prototype design and simulation analysis.Then,based on the theoretical analysis and model establishment of the flow sensor of the triboelectric nanogenerator,this paper carries out the design of the triboelectric non-full pipe flow sensor and determines the structure size of the principle prototype.Simulate and analyze the potential distribution of the sensing units under working conditions,verify the potential distribution of the sensing units under several specific states,and reveal its laws to determine the correlation between electrical signals and monitoring parameters.The feasibility of the flow monitoring principle was demonstrated through mechanism and simulation analysis,and a prototype of the triboelectric non-full pipe flow sensor principle was developed.Finally,an experimental system was established to control the liquid level and flow velocity,and a multi-parameter monitoring system for non-full pipe flow in large pipelines was developed.Then,a systematic study was conducted on the monitoring of liquid level and flow velocity,as well as the instantaneous flow error rate measured.For the liquid level sensing unit,the pulse number and trend of the voltage derivative curve are related to the liquid level,and the liquid level can be determined based on the positive/negative pulse number.For the flow velocity sensing unit,there is a good linear relationship between voltage and frequency of flow velocity,which can achieve accurate monitoring of flow velocity.Furthermore,to verify the accuracy of flow monitoring,three different flow conditions were selected from the range of 94 to 264 L/min to calibrate the measured flow with the actual flow,with a maximum error rate of less than 1.95%.In addition,the triboelectric non-full pipe flow sensor also has good responsiveness in sewage media,proving the usefulness of the sensor as a guide for flow measurement in scenarios such as sewage discharge and waste liquid treatment,and this work also promotes the development of triboelectric intelligent flow sensors in the field of fluid measurement technology. |
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