Electromagnetic Flow Tomography Technique Considering The Conductivity Distributions

The advanced multi-phase flow parameter measurement methods are of great significance for promoting energy and resource efficiency,and ecological environment protection.The flow velocity profile is one of the most important process parameters of multi-phase flow.Still,the existing methods have many problems in achieving the online measurement of flow velocity profile.Currently,it is difficult to satisfy the requirements of heterogeneous multi-phase flow measurement,which are frequently met in both academic types of research and engineering.In this paper,we study the measurement method of multi-phase flow velocity field,with a special focus on the electromagnetic flow tomography(EMFT)sensor.The mathematical model,measurement method,and system design have been investigated,which are evaluated with the numerical simulations,single-phase flow,and multi-phase flow experiments.1.In the research of EMFT mathematical model,the problem of measuring asymmetric velocity profile by electromagnetic flowmeter has been investigated.A model for dealing with the non-uniform conductivity distributions is proposed,extending the application range of EMFT into multi-phase flow.The feasibility of model has been evaluated by the electromagnetic and computational fluid dynamics simulations.The mean absolute error and correlation coefficient are employed for quantitative analysis,showing that the non-uniform model could offer better accuracy in measuring the flows of asymmetric velocity distributions.2.Regarding the system design,an EMFT sensor and measurement system has been designed and implemented,which could accommodate 2 excitation coil pairs and16 measuring electrodes.The measurement system consists of coil excitation module,voltage measurement module,current monitoring module and a micro-controller.The coil excitation module has two excitation modes,i.e.,the sinusoidal signal and threevalue square signal excitation modes.The voltage measurement module is composed of the low-pass filter,instrument amplifier,integration circuit,secondary amplifier circuit,and analog-digital converter circuit.Preliminary experiments show that the system can perform accurate measurements of the small changes in induced electromotive force from the opposing electrode pairs.3.Finally,the proposed model,sensor and measurement system are verified and tested by numerical simulation and multi-phase flow experiments.In the single-phase flow experiments,the system error of the measurement system performance has been evaluated and compared with a standard flowmeter.In the two-phase flow experiments,the influences of non-uniform conductivity distribution on the boundary measurements have been investigated by numerical simulations and experiments.The preliminary velocity field imaging results have also been presented,showing good consistency with the theoretical model.The effect of conductivity distribution on EMFT boundary measurement is verified.Finally,the researches are summarized and the suggestions are provided for future development.