Novel Approach for Analysis and Design of High-Speed Electrical Impedance Tomographic System for Void Fraction Measurements in Fast Two-Phase Flows

Electrical impedance tomography is a non-invasive imaging technique capable of void fraction measurements of two-phase flows at high-acquisition rates. This paper presents the design features of an in-house developed prototype fast EIT system and a 16 electrodes sensor. With simplified system architecture, the voltage of the excitation signal is controlled and the current is measured. The proposed full scan data collection strategy opens up new prospects for novel flow regime identification and image reconstruction techniques currently under development. A new calibration procedure that is based on the data from full scan strategy provides reliable absolute measurements in applications, where reference measurements are not available or reliable (e.g. gas-liquid flows with drifts of liquid phase temperature). Experimental results are compared with the analytical and numerical solutions. Fundamental studies for understanding the contact impedance give insight on the influence of important parameters: excitation frequency and liquid conductivity. The quality of the measurements at different frame rates is analyzed. The repeatability at 80 kHz of the prototype highlights similar figure of merit than reported fast EIT systems. The increase in frame acquisition rate allows up to 6250 frames per second for adjacent strategy and up to 833 frames per seconds for full scan strategy.