Numerical Simulation And Experimental Study On Principle Of Non-Intrusive Mass Flow Measurement

Flow measurement and flow status detection are basic applications for flow measurement in chemical production.During measuring flow,it is necessary to overcome the corrosive fluid medium in chemical production and the requirements of accuracy and pressure loss.Based on the full consideration of working environment and measurement requirements of the flowmeter,a new type of non-intrusive mass flow measurement principle is proposed in this paper.The principle of non-intrusive mass flow measurement takes use of the composite stress and strain changing with the fluid medium gravity and pressure,is acquired as the tube wall strain with the strain measurement technique,and the linear equation between differential strain and fluid flow can be established.In the end,the mass flow is calculated by the real-time acquisition of the wall differential strain to measure mass flow non-intrusively.Firstly,composite strain model of fluid medium pipe wall is derived by combining with the material mechanics,the elastic thin shell mechanics and the pipeline fluid mechanics.After careful analysis,the theoretical formula of the strain difference between the wall and the mass flow is obtained.On one hand,it can prove the feasibility of mass flow measurement principle based on the gravity field;on the other hand,it can lay a theoretical foundation for the following simulation analysis and experimental research.Secondly,taking into account that the wall strain is caused by both medium fluid and pipe structure,the fluid structure interaction(FSI)is used to simulate the wall strain.That is,Fluent module and Static Structural module in ANSYS Workbench are both adopted tocalculate the unidirectional FSI.To begin with,the flow state and pressure distribution was obtained at first with Fluent module,and then the pressure field was taken as the load condition to apply in the coupling surface of pipe and fluid in the Static Structural module,and solve the strain distribution under gravity field.According to the simulation data,the differential axial strain top and bottom was shown the linearity with the fluid flow,which can verify the feasibility of non-intrusive mass flow measurement.Based on the experimental platform in the laboratory,the strain collection and analysis system is built by using the full bridge strain gauge and uT7816 dynamic and static strain collection analyzer.According to the simulation results,the selection criteria for 4 high precision resistance strain gauge 1000? are posted at the midpoint of experimental pipeline(largest strain simulation value)of the top and bottom,which is composed of full bridge mode,and then access the measurement system to obtain the best data.The strain measurement system can acquire effectively the differential strain with sensitive response.After several experiments,the experimental results are recorded and processed.The fitting line between differential strain and mass flow shows a good linearity and sensitivity,which means the non-intrusive mass flow measurement can be an effective method to measure fluid flow effectively without destroying the flow state and provide a new way to measure flow for chemical plants and monitor flow state of pipeline.