A wire-mesh sensor for air-water two-phase flow imaging

Wire-mesh sensor is an intrusive sensor based on local instantaneous conductivity measurement in multiphase flows. A conductivity wire-mesh sensor measurement system is designed to image the horizontal air-water two-phase flow. The proposed wire-mesh sensor consists of two planes of parallel 16 electrodes which cross under an angle of 90° and are installed across a pipe with 50mm inner diameter, so the local conductivity of the fluid at crossing points can be measured. Data acquisition system is composed by an excitation module, a multi-channel switching module, a signal conditioning module and a multi-channel data acquisition module. The logic control of time multiplexed excitation and re-trigger acquisition is realized by the cooperation of a PXI modular instrument and a FPGA. The sensor can operate at a time resolution of 200 frames/s and a spatial resolution of 3.1 mm. Flow imaging is presented in two ways: cross-sectional image and axial slice image along the central chord of the pipe in axial direction. Sensor validation indicated that the proposed system has a good stability and effectiveness. Dynamic tests of flow imaging of bubbly flow, plug flow, stratified flow, slug flow and annular flow were conducted, which can provide detailed information about the flow conditions.