Gas Volume Fraction Measurement and Re­Tomography of Gas­ Liquid Annular Flow with ERT Based Data Fusion

Fusheng Zhang, Feng Dong, Chao Tan

Tianjin Key Laboratory of Process Measurement and Control, School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China

Tel: 86­22­27890276, Fax: 86­22­27892055, Email: fdong@tju.edu.cn

ABSTRACT

Gas­liquid annular flow widely exists in many industrial processes. Accurate process parameter measurement and online monitoring are urgent issues to the researchers worldwide. Data fusion with some particular merits has been paid more and more attention in multi­phase flow researching field recently. In this work, gas volume fraction of gas­liquid annular flow in a horizontal pipeline is measured by a 16­eclectrode electrical resistance tomography (ERT) system with data fusion method. The reconstructed images of annular flow are reprocessed with the gas volume fraction result to make the images more approaching to the real flow state, called re­tomography in this work. A function fusion architecture including Dempster­Shafer (D­S) evidence theory in the decision fusion level is put forward. Flow regime recognition is carried out to improve the parameter measuring accuracy and gas volume fraction is calculated right after the correct recognition. Electrode voltage data is independent and paralleled measured by the system, so every electrode can be considered as a homogenous sensor in the fusion system. Excitation voltage and non­excitation voltage are separately treated, the former part goes to the flow regime recognition and the latter part goes to the gas volume fraction calculation after data sequence arrangement. The experiment results show that this fusion method could efficiently recognize the flow regimes with proper accuracy and the relative error of gas volume fraction measurement is within ±10%. The re­tomography method is feasible and meaningful to the flow state monitoring of annular flow.

Keywords Gas liquid annular flow; Gas volume fraction; Retomography; Electrical resistance tomography Data fusion