Master of Science in Mechanical Engineering (MSME)
Due to growing energy demands and the need for increased fuel consumption efficiency, environmental protection agencies are imposing more stringent emissions regulations on gas turbine combustion systems with emphasis on NOx emissions reduction. Emerging technological combustion schemes to reduce NOx commonly employ lean premixed combustion. Decreases in NOx are globally obtained by flame temperature decrease and locally improved by homogeneity of the reacting mixture. A new micro fuel injection swirler, capable of providing efficient and rapid mixing over a short distance, is presented in this thesis. The conception of the Micro Fuel Injection Swirler (MFIS) was motivated by the need for enhanced mixing devices in lean premixed combustion and the capabilities of a micro manufacturing technique developed at Louisiana State University in conjunction with Mezzo Technologies. The MFIS uses a circular array of porous panels manufactured with an internal fluid cavity which allows for micro scale fuel distribution. The fuel is injected perpendicular to the blade opposing the oncoming stream of air which produces a highly turbulent swirling flow to enhance combustion stability at ultra lean operation necessary to reduce NOx emissions. A process was developed to fabricate and assemble the MFIS economically and reliably while ensuring dimensional stability. A benchmark swirler was also manufactured with similar dimensions as the MFIS but none of the inherent geometry characterizing the advantages of the MFIS. A combustion chamber was designed and fabricated to provide testing infrastructure for verifying the performance of the MFIS. Combustion results indicated that the MFIS was capable of achieving relatively lower equivalence ratios at LBO compared to benchmark cases tested. At a set equivalence ratio, the MFIS produced higher flame temperatures, higher heat release rates, and comparable NOx emissions. At equivalent operating temperatures, the MFIS produced nearly equal NOx emissions compared to the perfectly premixed case. Hydrogen testing showed that the lean blowout limits could be extended with hydrogen addition, providing further reduction in NOx while allowing stable combustion. In summary, the MFIS was capable of providing efficient air/fuel mixing over a short premixing distance, affirming its effectiveness in lean premixed combustion systems.
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Giglio, Anthony Louis, "Design, Fabrication, and Testing of a Micro Fuel Injection Swirler for Lean Premixed Combustion in Gas Turbine Engines" (2008). LSU Master's Theses. 3158.