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Advanced imaging and measurement for multiphase flow

Final Activity and Management Report Summary - AIMMF (Advanced imaging and measurement for multiphase flow)

The principal aim of this project was to investigate, validate and actualise a novel multiphase flow metering scheme with the application of process tomography combining other sub-systems, and multiphase flow modelling technique. The merits of the new scheme against the traditional method is that, the local flow information as cross-sectional phase fraction and velocity distribution can be acquired based on the local structure imaged by tomography technique invasively and in real time, while the traditional approach usually cannot do it online and must use complex separator / branch / manifold system to get single phase parameters. Since the new scheme reflects the non-uniform flow distributions in space and time, and is able to simplify the production system and process, it could reduce the instrument and operation cost greatly. Therefore, the overall long-term objective was to develop a new generation of non-invasive flow instrument for the in-situ online measurement of flow-rates and imaging of the internal structure of complex, unsteady two- or three-phase flows in coming future, which is significant for both multiphase flow study and industrial applications.

The research is multidisciplinary covering the aspects of multiphase flow mechanics and metering, process tomography, signal processing and multi-variable data fusion. Four sub-systems, namely, Electrical impedance tomography (EIT), Electromagnetic flow meter (EMF), Venturi and Online density meter (ODM), is potentially able to measure the volumetric flow rate of each phase in three-phase flows with a conductive continuous liquid phase, as well to extract time dependent distributions of the local velocity and volume fraction distributions of the dispersed phases, and to further visualise complex flow patterns. Considering the complexity of multiphase flow, only vertical upward dispersed flows (oil / gas as bubbles in water) with a conductive continuous liquid phase are targeted within the scope of this research.

During the incoming phase, the oil-in-water flow and air-water flow were studied. This project was for the return phase, and the target included two main aspects: one is the gas-oil-water flow overall test; the other is the integration of the data analysis and fusion method, namely, software development.

For the former, the flow loop was reconstructed to establish a vertical section of approximately four meters high, and the four main sub-systems, i.e. EIT, EMF, Venturi and ODM were installed and tested under different flow conditions. Due to the difficulty increased significantly in three phase flow, the flow parameters were controlled carefully to produce a relatively stable bubble flow.

For the latter, an analysis software platform with user-friendly interface assembled with all the processing and correction method also the full graphical display function was developed. Based on this research, the scheme based on tomography technique was evaluated under gas-oil-water three phase bubbly flow, theoretical correction (drift flux model and frictional pressure drop calculation) was adopted, and data analysis and fusion method was developed and integrated as a software platform. Various factors including the hardware performance, reconstruction algorithm, fluid properties and flow characteristics, flow modelling was analysed to improve the integrated accuracy.

The output demonstrates the feasibility of the proposed scheme and provides a good base for further in-depth research, as well reveals the detailed challenges in gas-oil-water three phase metering and indicates the specific research directions.