Flame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NOx emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic instabilities which can induce global blowout and termination of the combustion process. The work in this thesis is focused on identifying the mechanisms of flame extinction and controlling these mechanisms via pressure gradient tailoring. This is accomplished within a premixed blow-down combustion facility utilizing a bluff body flame stabilizer where flame extinction is induced by removing the flow of fuel into the reactant mixture. CH* chemiluminescence imaging and high-speed particle imaging velocimetry (PIV) are used to determine the flame boundary and resolve the reacting flow field, respectively. The mechanisms of flame extinction are attributed to the changing vorticity dynamics within the flow field as the equivalence ratio is reduced, which will directly influence the strain rate experienced by the flame. To influence these vorticity dynamics, the test section walls are manipulated to alter the downstream pressure gradients. It is determined that increasing the magnitude of the downstream pressure gradient increases the growth of the strain rate and vorticity experienced by the flame.
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Master of Science in Mechanical Engineering (M.S.M.E.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Mechanical Engineering; Thermo-Fluids
Length of Campus-only Access
Masters Thesis (Campus-only Access)
Morales, Anthony, "Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring" (2018). Electronic Theses and Dissertations, 2004-2019. 6082.