A New Method of Measuring Velocity Profiles using a MultiElectrode Electromagnetic Flow Meter

This paper describes a model of a novel design of electromagnetic flow meter for velocity profile measurement in single phase and multiphase flows with nonuniform axial velocity profiles. A simulated Helmholtz coil is used to produce a uniform magnetic field orthogonal to both the flow direction and the plane of an electrode array embedded on the internal surface of a nonconducting pipe wall. Induced voltages acquired from the electrode array are related to the flow velocity distribution via variables known as ‘weight values’ which are calculated using COMSOL Multiphysics software. Matrix inversion is used to calculate the velocity distribution in the flow cross section from the induced voltages measured at the electrode array. This paper presents simulations including, firstly the effects of the velocity profile on the electrical potential distribution, secondly the induced voltage distribution at the electrode pair locations, and thirdly the reconstructed velocity profile calculated using the weight values and the matrix inversion method mentioned above. The flow pipe crosssection is divided into a number of pixels and the mean flow velocity in each of the pixels is calculated from the measured induced voltages. Reference velocity profiles that have been investigated include a uniform velocity profile and a linear velocity profile. The results show good agreement between the reconstructed and reference velocity profiles. The results presented in this paper are most relevant to flows in which variations in the axial flow velocity occur principally in a single direction

Measurement of velocity profiles in multiphase flow using a multi-electrode electromagnetic flow meter

A Helmholtz coil is used to produce a near-uniform magnetic field orthognal to both the flow direction and the plane of an electrode array mounted on the internal surface of a non-conducting pipe wall. Induced voltages acquired from the electrode array are related to the flow velocity distribution via variables known as 'weight values' which are calculated using finite element software. Matrix inversion is used to calculate the velocity distribution in the flow cross section from the induced voltages measured at the electrode array. Experimental results are also presented for the reconstructed velocity profile of the continuous water phase in an inclined solids-in-water multiphase flow for which the axial water velocity distribution is highly non-uniform. The results presented in this paper are most relevant to flows in which variations in the axial flow velocity occur principally in a single direction

A numerical approach to determine the magnetic field distribution of an electromagnetic flow meter.

This paper addresses the design of a novel electromagnetic flow meter for use in multiphase flows. The relationship between the magnetic field distribution, the induced electrical potential and the velocity distribution of the conducting continuous phase was studied using COMSOL Multiphysics software (formally known as FEMLAB). The electromagnetic flow meter was modelled to its physical specification i.e. a PTFE pipe located within a Helmholtz coil. The Helmholtz coils were used to produce a magnetic field which was orthogonal to both the flow direction and to a chord joining the detection electrodes. At any instant in time, the magnetic flux density was uniform in the flow cross section. Using the model, the position of the electrodes could be changed to anywhere on the internal surface of the insulating PTFE wall of the flow meter - to satisfy the project requirement of measuring the induced electrical potentials at specific locations on the boundary of the flow

Using the four-sensor probe to measure the bubble velocity vector in bubble water two phase flow

This paper describes the new design of the local four-sensor probe which was used to measure the velocity vector of the bubbly gas-liquid two phase flow in the pipe which diameter is 80mm. The bubble velocity vector can be calculated from seven time intervals taken from the output signals from each of four conductance sensors located within the local four-sensor probe. Based on the four sensor probe signals, a new signal processing technique was introduced which can improved the accuracy of the measurement results. The test results of bubbly flow in the tank, in the flow loop and the bubbly, swirling flow are presented in this paper as well. The four-sensor probe can be used as a calibration method for the dual-plane EIT system

Two-phase flow meter for determining water and solids volumetric flow rate in inclined solids-in-water flows

This paper describes the design and implementation of a two-phase flow meter which can be used in solids-in-water two phase pipe flows to measure the in-situ volume fraction distributions of both phases, the velocity profiles of both phases and the volumetric flow rates for both phases. The system contains an Impedance Cross Correlation (ICC) device which is used in conjunction with an Electromagnetic Velocity Profiler (EVP). Experimental results were obtained for the water and solids velocity and volume fraction profiles in upward inclined flow at 30 degrees to the vertical, in which non-uniform velocity and volume fraction profiles occur