Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Kopp, Gregory A.

Abstract

Gas flares have been distinguished as a potential major source of hydrocarbon emissions from refineries and chemical plants. Flaring is the burning of waste gasses through a flare stack or other combustion device. By generating atmospheric turbulence in wind tunnel, an in-depth study has been conducted to capture the mechanics involving the reactive jet and stack-wake regions, which resembles the real world scenario of gas flaring, but at a reduced scale. In this study, a methodology has been described to generate atmospheric turbulence by passive grid to obtain the ideal turbulence intensities (Iu) and length scales (Lx) for model flare stacks.

The entire flame is depicted by capturing flame images using multiple cameras. It is examined how the upstream turbulent flow interacts with non-premixed reactive jets at low velocity ratios. The size of the recirculation zone decreases with an enhanced turbulent cross-wind. In addition to that, a comprehensive study of discrete flame packets are carried out using instantaneous images. The colour of the flame is closely analyzed in order to distinguish the mixing phenomena of crossflow fluid and jet fluid in the near field. Moreover, empirical equation is proposed for predicting flame length in the presence of cross-wind. The changes in flame length, discrete flame packets, and colour are monitored for the different upstream turbulent cross-wind. It is observed in the current study that cross-wind turbulence affects the flame lengths, wake recirculation zone, vertical and lateral spread of the flame.

Summary for Lay Audience

Gas flaring from industrial establishments and production sites are a common real world phenomenon. In 2012, researchers report tracking flares using an instrument aboard a NASA weather satellite that takes images of Earth in infrared and visible light which indicated that the total flared gas volume was approximately 143 billion cubic meters (BCM), corresponding to 3.5% of global production. Flared gas contributes significant to global warming since the burned product CO2 is directly responsible for enhancing greenhouse effects. Johnson and Kostiuk(2002) reported that some of the flared gas remain unburned due to the presence of strong cross-wind. The unburned fuel (specifically methane) is twenty times more harmful in causing greenhouse effects.

In the current study, atmospheric turbulence is generated in reduced scale in the wind tunnel. Gas flaring phenomena is observed for different turbulence conditions. Multiple cameras are used for flame visualization. An empirical equation is provided to predict flame length for methane rich fuel. The changes in flame length, discrete flame packets, dispersion or spread of visible flame, and the colour of flames are monitored for the different upstream turbulent conditions. The current study has showed that crossflow turbulence affects the above mentioned properties. The current study suggests that tracking unburned fuel to identify turbulence effects on flaring phenomena.

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