Flow Structure of an Annular Gas-Liquid Swirling Flow

  • Rafael González Hernández

Student thesis: Master's Thesis

Abstract

The main purpose of this work is to study experimentally, the characteristics of swirling flow interacting with a circular bluff body. The experimental setup consists of a 12.9 m horizontal water loop. The test section is made of a plexiglass pipe with 0.61 m of length and 0.041 m of internal diameter. Swirl flow is generated inside the transparent pipe, using a swirl cage. A circular bluff body is placed inside the test section. Both, air and water flows are controlled by flow valves and measured with independent flow meters. The experimental methodology is based on two approaches. The first approach was performed using high-speed photography technique over a range of water and air flow rates. Different values of Gas/Liquid flowrate Ratio (GLR) were used. The selected flow rates were chosen to complete the experimental results of a previous work held in our laboratory [1,2]. The information extracted from the high-speed photography includes air core diameter, air core tip distance from the swirl cage, helical angles, wavelengths and air core dynamics. Experiments were performed for three different position of the bluff body inside the tests section. For air core geometry, it was found that the air core diameter and air core length from the swirl cage rapidly grow when GLR reaches 1.6%. Above the critical GLR value of 2.5% both, both diameter and length of the air core remain stable. It was observed that helical angles and wavelengths, appearing on water-air interphases, are not affect by GLR or the position of the bluff bodies. In addition, a flow regime map was established for three observed patterns, (i) air core tip far from the circular bluff body, (ii) air core tip close to the bluff body with presence of an air pocket and (iii) air core tip touching the bluff body. Regarding the air core dynamics, it was observed that the air core fluctuates around its axis. The air core diameter showed a periodic behavior that was analyzed performing a Fast Fourier Transform. A hydraulic jump was characterized along the length of the pipe. A wavelength having identical characteristics was measured before and after the hydraulic jump. The second experimental method is based on Stereo-Particle Image Velocimetry. The 3- dimensional velocity distribution of single phase swirling laminar flow is obtained. In Cartesian coordinates, it can be observed that the horizontal (along pipe axis) and vertical (perpendicular to the pipe axis) velocity components are zero and maximum, respectively, at the center of the pipe. In opposite near the pipe walls, the horizontal velocity is maximum with a minimum vertical component. The third component of the velocity (depth) is symmetric with opposite velocities from the center of the pipe. The obtained 3D velocity distribution shows clearly the presence of a swirl flow inside the single-phase flow. Obtained measurements in this thesis report can be helpful for developing and/or validating future numerical models.
Date of AwardDec 2021
Original languageAmerican English

Keywords

  • Turbulent Swirling Flow
  • Liquid–Gas Separation
  • Circular Bluff Body.

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