Research On On-line Metering System For Low-level Non-full-pipe Wastewater

Base on Electromagnetic Flowmeters is not affected by the characteristics of the measured fluid,and has high accuracy and wide measuring range,Electromagnetic Flowmeters is generally used for the measurement of the quantity of waste water flow of the non-full pipe.However,the electrode of Electromagnetic Flowmeters must be located in the measured fluid.When fluid's liquid height is lower depth ratio(10% of the pipe diameter),the electrodes cannot be fully immersed in the measured fluid,making it difficult to collect signals.In order to solve the problem that quantity of flow is difficult to measure when the measurement of the quantity of flow of the non-full pipe and the fluid's liquid height are in low liquid level,this paper proposes a new measurement of low liquid level quantity of flow of the non-full pipe: Based on the measured liquid level height value of the theory of communicating combined with high-precision laser rangefinder,the breather pipe above the pipeline combined with the current meter accurately measures the average flow velocity of the fluid in the pipeline,and the flow value is obtained by the Volume Floweate formula.Pipe roughness and fluid viscosity have a certain effect on flow measurement.In order to study the effect of pipe roughness and fluid viscosity on flow measurement in non-full-pipe flow measurement,FLUENT simulation software was used to simulate different roughness and viscosity.Velocity distribution cloud diagram,the roughness-average velocity and viscosity-average velocity models were established.Before the experimental platform was built,the FLUENT simulation software was used to simulate the gas-liquid two-phase flow in the pipeline,and the installation position of the U-shaped pipe was determined to be 1m to 2.5m from the water inlet,and the diameter of the U-shaped pipe was 0.02 m.Build a platform based on the simulation results,and compare the flow value obtained through the model with the measured value of the electromagnetic flowmeter.The results show that when the liquid level is lower than 0.1D,the flow measurement error is less than 1.70%,the results show that when the liquid level is higher than 0.1D,the flow measurement error is less than 1.80%.The flow rate is calculated by the average flow velocity values obtained from the roughness-average flow velocity and viscosity-average flow velocity models,and the error of the calculation result is less than 3.03%.Experiments verify the feasibility of the method and the reliability of the model.It is suitable for low-level non-full-pipe flow metering.