Use of Local Conductivities, Measured at Pre-Determined Centres of Action (CoA), for Image Reconstruction in Multiphase Flow
Onilude1* & G. P. Lucas1
1 School of Computing & Engineering, University of Huddersfield Queensgate, Huddersfield UK. (HD1 3DH)
In multiphase flow measurement applications, tomography is often required to reconstruct the local volume fraction distribution of a low conductivity dispersed phase flowing within a high conductivity continuous phase within the confines of a pipe of circular cross section. Conventional Electrical Resistance Tomography (ERT) techniques for performing this task are regarded as soft field measurements, making these techniques ill-posed. Among the generally accepted solutions for reconstructing the local conductivity distribution, and hence the local volume fraction distribution has been the use of algorithms which are based on assumptions such as the use of a-priori information and then updating the information iteratively. To improve spatial resolution high computing capacity is required. In this paper, an alternative technique, which employs a concept requiring lower computing requirements, is described. The technique uses measurements of the local conductivity at predetermined Centres of Action (CoAs) to determine the local volume fraction distribution of the dispersed phase. The only a-priori information required is the positions of the Centres of Action associated with different electrode configurations – each configuration comprising a different combination of groups of electrodes, with each group being configured as either an excitation source, a current detector or as an earthed guard. A further major advantage of this novel technique, compared to conventional ERT methods, is that a very high number of different electrode configurations are possible – allowing regions that are either close to the pipe wall and or further towards the centre of the pipe to be successively interrogated. Experimental results carried have shown good agreement with reference measurements.
Keywords: Electrical resistance tomography (ERT), conductivity, centre of action (CoA), local volume fraction
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