Current Signal versus Voltage Signal of Excitation Source in Wire Mesh Tomography: A Simulation Study
Abstract
Wire mesh tomography (WMT) is widely used to investigate liquid-gas two-phase flow and single-phase mixing processing. A common approach in wire mesh tomography is to apply a voltage as a source and measure the current at the receivers. However, it is believed that by exciting a current signal at the transmitter, it will increase the signal distribution because of the positioning of the wire mesh itself. Thus, the objective of this paper is to propose the current excitation source at the transmitter and measure the voltage at the receivers. Based on AC/DC physics studies, a 3D simulation using finite element model software (COMSOL Multiphysics) was used to draw a 3D wire mesh sensor and get the sensor readings. A MATLAB software was used to reconstruct the tomograms of WMT. Besides, the wire mesh sensor was tested in a vertical liquid/gas two-phase flow process column with a nominal diameter of 30 mm. A single wire-mesh sensor with 8 x 8 electrode wires was used with a temporal and spatial resolution of 10 kHz, 5V voltage, and 4 mA current. Different bubble conditions of liquid-gas in the pipe were tested. Hence, the sensor reading performance and tomogram of the region of interest were obtained and analyzed. The image became more visible for the bubble with a radius of 19 mm by exciting the voltage at the transmitter. It can be proven that the gas phase cross sectional area, AG, for a bubble with a radius of 19 mm is higher than 10 mm and 4 mm, which is 2120.575 mm2 or 75%. Besides that, by exciting the current, the gas phase cross-sectional area, AG, for a bubble with a radius of 19 mm was 989.6 mm2, or 35%. However, when using current excitation as a source to detect tomograms in two-phase flow, more research is required.
