Study On Capacitance Measuring System Of Gas-liquid Two-phase Flow In Minichannels

Multiphase flow phenomena in industry have the tendency towards channel size miniaturization. However, Lack in parameter measuring methods has bottlenecked the development of two-phase flow in minichannels of the millimeter level. Nowadays, the minichannel parameter measurement is the current research focus in multiphase flow study. Electrical capacitance detection is a classical measuring method which has advantages such as non- intrusiveness, simple structure and low cost but is scarcely used in 1-5 mm channels. This thesis aims to apply the electrical capacitance method to minichannel gas-liquid two-phase flow parameter measurement. A capacitance sensor and the relevant parameter measuring system are designed and constructed to study flow characteristics and flow velocity in minichannels. Main works and innovation points are listed as follows:(1) A capacitance sensor is designed and made for capacitance measuring in minichannels, along with implementation of the whole system. Gas-liquid flow in 3 glass pipes with inner diameters of 4.0mm, 3.1mm and 1.8mm are measured. Results show that the electrical capacitance method is feasible and effective in minichannel two-phase flow parameters measuring.(2) Preliminary analysis of capacitance signals are done using time-domain statistical analysis, Fourier analysis, wavelet analysis and Hilbert-Huang transform methods to study flow characteristics. They are compared with flow condition in ordinary channels. It is proved that capacitance signals are feasible in flow characteristics analysis and flow pattern identification.(3) Capacitance signals are studied using cross-correlation method to detect velocity. The experimental result is very good.