A High Adaptive Electrical Impedance Sensing System For Flow Measurement

M. Wang, W. Yin

Centre for Particle & Colloidal Engineering

School of Process, Environmental & Materials Engineering, University of Leeds, Leeds, LS2 9JT, UK

E-mail: minwy@leeds.ac.uk

ABSTRACT

As a generic 'tool' electrical impedance tomography (EIT) is useful in improving the modelling and the design of many complex processes and for process control (Williams 1995; Neuffer, 1999). However, the present developments of the EIT technique are only applicable to the aqueous-based fluids that possess continuous admittance property (Xie, 1994). For example, it would not be suitable for a stratified flow or an intermittent flow in a horizontal channel or large bubble formation and foams since some of the electrodes may lose contact with the conductive fluid.

A preliminary study of a novel sensor and apparatus is reported in the paper. This study seeks to address some significant shortcomings in the application of EIT through the use of a new sensing strategy and apparatus for measuring complex multiphase flows, such as the oil/gas/water flow or bubble formation and foams. The major feature of the sensing system is to employ one conductive ring as a tomographic sensor instead of a number of electrodes in conventional EIT. The sensing strategy facilitates a more homogeneous sensitivity distribution through the sensing domain within the conductive ring, which is less affected by the contact area or geometry of electrodes than encountered in previous EIT systems. The sensor can be conveniently constructed as a flange-based flow sensor, if required, without necessitating drilling of holes into the pipe wall. Therefore, it provides a realistic way for measuring the dynamic changes of flowing fluids. The novel methodology is believed to offer a significant advance in enabling a more flexible and robust EIT system to be devised for on-line measurement and control of flow in oil, pharmaceuticals and food industries.

Keywords Electrical Resistance Tomography (ERT), flow measurement, adaptive sensor; optimum design