A Novel Void Fraction Measuring Method For Gas/Liquid Two-phase Flow Based On Cross-sectional Resistive Information

Void fraction is an important parameter to gas/liquid two-phase flow measurement, and it is extremely significant to measure void fraction accurately. Detecting techniques for flow parameters, especially for void fraction, are presented in this paper. Considering the instant measurement of electrical methods, and other advantages like simple structure, low developing cost and easy to realize, it has been widely payed attention in industry. Basing on the summarization of electrical methods, a new measuring technique with cross-sectional electrical impedance information is brought forward, which establishes a parallel electrical field with multi-electrodes exciting, then the information of void fraction can be extracted from the boundary measured data.The main achievements of paper are as follows:1. The mathematical model for a multi-electrodes excited parallel electrical field is established. Some analytic solutions under special conditions are presented, which have been proved by numerical solutions in simulations.2. Descreption of the uniformity of sensing field has been made, and the affecting factors have been analyzed, which consequently provide justifications for designing electrode and choosing exciting strategy.3. The characteristic value for cross-sectional void fraction has been extracted basing on the analysis of 16-electrode parallel field.4. The void fraction is measured at different phase distribution in two-phase flow with simulations. The measured results are analyzed, which leads to a conclusion that the method could reflect void fraction effectively.5. Concerning the analysis mentioned above, some feasible improvements were investigated with the discussion on merits and defaults for each improvement. The discussions show that introducing a conductive annular item could well improve the electrical field uniformity in the circumstance of single medium, which was validated by numerical methods.6. The scheme of adding a weakly conductive annular item was adopted, and performance of the improved measuring system was compared with the originals. Finally, the conclusions say that the results were much preciser when measuring litter void fractions, which was attributed to the improvment of the electrical field uniformity.