Systematic Frequency and Statistical Analysis Approach to Identify Different Gas–Liquid Flow Patterns Using Two Electrodes Capacitance Sensor: Experimental Evaluations

Abstract

This work proposes a method to distinguish between various flow patterns in a multiphase gas–liquid system. The complete discrimination between different flow patterns can be achieved by mapping the corresponding frequency and statistical parameters. These parameters are usually obtained from further analysis conducted on the signal data of the utilized sensor. The proposed technique is based on establishing interrelationships between these parameters, namely the mean (m), the standard deviation ( σ ¯ ), power spectral density (PSD), the width of the characteristic frequency peaks (Δƒ), the skewness ( γ 1 ) and the kurtosis ( γ 2 ). Therefore, a relatively simple electrical capacitance sensor with two electrodes was designed and implemented on a two-phase flow apparatus with a circular pipe. The experimental operating conditions comprised of different combinations of air–water superficial velocities at three inclinations (i.e., horizontal, upward 15° and upward 30°). This research discusses in specific the analysis underlying flow patterns identification method and the rationale for selecting the proposed approach. The results showed that some parameters found to be more valuable than others such as m, σ ¯ and Δƒ. Besides, combining two sets of these statistical graphs which are (a) σ ¯ vs. Δƒ with Δƒ vs. m (or Δƒ vs. total power), (b) Δƒ vs. total power with γ 1 vs. σ ¯ (or γ 2 vs. σ ¯ ), and (c) σ ¯ vs. m with Δƒ vs. m (or Δƒ vs. total power), allowed all flow patterns field to be identified clearly at all inclinations. It is therefore concluded that for any gas–liquid multiphase flow system, the reported approach can be used reliably to discriminate between different generated flow patterns.

A Simplified Numerical Approach to Examine the Sensitivity of Two-Electrode Capacitance Sensor Orientation to Capture Different Gas–Liquid Flow Patterns in a Small Circular Pipe

“…The experimental operating conditions consist of (a) different combinations of gas–liquid (i.e., air and water) superficial velocities, and (b) different tested inclination angles (i.e., 0°, +15°, +30°). The configuration of this setup and the initial operating conditions allowed the development of all the well defined multiphase gas–liquid flow patterns [ 28 , 32 , 33 ]. The setup was designed to operate with water as the liquid phase at the superficial velocity between 0 and 1.06 m/s, and with air as the gas phase the superficial velocity is between 0 and 5.0 m/s.…”

“…The two-electrode capacitance sensor electrical design principle, methodology and details are influenced by the research offered by Ferry (1997) and Jerzy (2008) [ 35 , 53 , 54 ]. More details on the sensor functionality, calibration procedure, responsiveness test, and validation against the experimental measurement are found in Al-Alweet et al (2020) [ 32 ]. The designed sensor captured the generated flow patterns with an accepted accuracy.…”

“…As a result of the aforementioned configuration and the operating conditions, comprehensive maps were developed for all the tested inclinations. These maps identify each flow pattern by its visual observed characteristics and the range of gas–liquid superficial gas velocities (The operating procedure shown in more detail here: [ 32 ]). The summary of the developed maps is presented in Table 3 .…”

“…In this work, the focus is on finding the optimum orientation (i.e., side-to-side or top-to-bottom) of the sensor which will help to conduct a full design analysis by obtaining the electrical field distribution and the capacitance values inside the simulated pipe. A simple simulation approach in COMSOL multi-physics was utilized to simulate (a) the typical flow patterns developed inside a circular pipe of a multiphase gas–liquid flow, and (b) the actual sensor and its geometrical model (which is similar to the actual experimental designed capacitance sensor, [ 32 ]). Figure 3 shows the computational domain of 12 × 7 × 7 cm, an arrangement defined to reflect the geometrical configuration of the sensor and the pipe.…”

“…To validate the numerical approach used in this work, selected samples of the time-dependent values of the simulated cases and the experimental values were compared (which will be shown and discussed in the next section). The discussion of all the performed experimental flow patterns that are reported in Table 3 and its hydrodynamic characteristics are found in more detail in Al-Alweet et al (2020) [ 32 ]. Again, this work was focused on the selection of the optimum orientation of the designed concave two-electrode capacitance sensor through a numerical approach.…”