A novel conductivity probe for measurement of bubble in gas-liquid two-phase flow

Conventional dual-tip conductivity probe is commonly composed of a metal casing and multiple needles. In order to mitigate the interference of the flow field caused by probe structure, the needles are wrapped by insulation, and the casing is kept away from the tips. However, this structure extends the sensitivity range of the detection tip, limits the size of the probe and consequently introduces more measurement error. In this paper, a new type of conductivity probe is developed for gas measurement in gas-liquid two-phase flow. Unlike conventional dual-tip probe, the new probe no longer requires a casing, but instead integrates the excitation electrode and both measurement electrodes on a single needle. The integrated structure not only reduces the overall size, but also shortens the spacing between the excitation and measurement electrodes. The electric field analysis shows that the sensitive range of the measurement electrode can be effectively controlled under the new structure. In the experiments of gas-liquid flow with bubbly, slug and churn flow, the measurement signal quality of the new probe and the conventional dual-tip probe were comparative analyzed based on the relative error of gas void fraction, the maximum correlation coefficient and the effective signal yield. The results indicate that each parameter of the new probe is superior to that of the general probe, especially in the bubbly flow dominated by small-sized bubbles.