An analysis and interpretation of the signals in gamma-absorption measurements of liquid–gas intermittent flow

Abstract

The intermittent flow (slug and plug type) of liquid-gas mixtures in a horizontal pipeline measured by the specific radiometric apparatus is presented. The measurement system consists of two sources of Am-241 gamma radiation and two scintillation probes. An analysis of the signals measured by the radiometric equipment is performed in the domain of time and of frequency. Recognised signal parameters are directly referred to physical quantities associated with a liquid-gas flow. The employed methodology enables determination of gas-phase flow velocity and estimation of the average depth and length of bubble gas structures. In the paper, the processing and interpretation results of the selected experiment are presented to show the in-depth description of gas structures and the type of flows recognition.

Analysis and interpretation of radiometric signals in a liquid-gas bubble flow

“…In presented experiments, the air was injected to the pipeline test section through a special nozzle generating a dispersed bubble flow. In contrast to the slug flow [10,15,16], in the bubble flow the bubbles do not have a free surface and are very small, in the order of a few mm. In the further section of the pipeline, bubbles forms clusters, as shown in Fig.…”

“…Depending on the velocity of the liquid phase and the expense of gas injected, the different flow regimes can be obtained: stratified, slug, plug and bubble. The measuring system has been described in detail in [9,10]. It consists of a radiometric set (two NaI(Tl) scintillation probes and two Am-241 gamma-ray sealed sources), an ultrasonic flow-meter and a gas flow controller.…”

“…The gas phase velocity is determined based on a cross-correlation analysis of signals obtained from two scintillation probes. More information on crosscorrelation analysis in radiometric measurements of twophase flows can be found in [10,11].…”

“…6 where time duration t k for 50 first peaks is shown. Similarly to analyses presented in [10], t k was related to the cluster's length by the following relationship:…”

“…where: u B (t k )uncertainty of duration time t k , u c (υ G )combined uncertainty of gas velocity [9][10][11]. The values of l k for the first 50 clusters of bubbles, together with the average value (black line), are shown in Fig.…”