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Lieuwen, Timothy C.

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Now showing 1 - 10 of 19
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    NOx Production from Premixed Hydrogen/Methane Fuel Blends
    (Georgia Institute of Technology, 2023-09-01) Breer, Benjamin R. ; Godbold, Conner W. ; Emerson, Benjamin L. ; Sun, W. ; Noble, Bobby ; Lieuwen, Timothy C.
    Hydrogen (H2) fuel is a promising means for long duration energy storage and dispatchable utilization of intermittent renewable power, which can be combusted without CO2 emissions. However, combustion of any fuel in air can still lead to NOX production. This whitepaper summarizes recent analyses of NO emissions of premixed H2/CH4 blends, demonstrating how fundamental drivers of NOX production change with hydrogen addition. Three major findings are presented: (1) At constant temperature, NO emissions decrease with the addition of H2 for typical gas turbine conditions; (2) Although NOX emissions are typically quoted as parts per million (ppm), it is not appropriate to use ppm as a comparison between different hydrogen blended compositions; one must use mass based comparisons (e.g., ng/J or lbm/MMBTU); (3) atmospheric pressure fuel sensitivity NOX studies will not capture the controlling NO production physics that are present in practical applications, such as gas turbines. These results provide important context for several experimental studies that have been reported. First, they are consistent with several recent demonstrations of fielded gas turbines with hydrogen blending, that show constant to declining NOX levels with hydrogen addition. Second, some lab studies have noted that hydrogen blended systems have elevated NOX emissions relative to natural gas, but these appear to be for nonpremixed systems and it is not entirely clear what is being held constant for these comparisons (temperature, power, etc.). Given the strong temperature sensitivity of NOX production, these results cannot be applied more generally to understand NOX emissions tendencies. Taken together, we conclude that utilization of modern premixing combustion technologies with hydrogen blending should lead to constant or decreasing NOX emissions, but use in older, diffusion type burners can lead to elevated NOX. item_description: This whitepaper summarizes recent analyses of NO emissions of premixed H2/CH4 blends, demonstrating how fundamental drivers of NOX production change with hydrogen addition. Three major findings are presented: (1) At constant temperature, NO emissions decrease with the addition of H2 for typical gas turbine conditions; (2) Although NOX emissions are typically quoted as parts per million (ppm), it is not appropriate to use ppm as a comparison between different hydrogen blended compositions; one must use mass based comparisons (e.g., ng/J or lbm/MMBTU); (3) atmospheric pressure fuel sensitivity NOX studies will not capture the controlling NO production physics that are present in practical applications, such as gas turbines.
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    Pollutant Emissions Reporting for Ammonia Fuel Blends
    (Georgia Institute of Technology, 2022-11-04) Douglas, Christopher M. ; Steele, Robert ; Martz, Tom ; Noble, Bobby ; Emerson, Benjamin L. ; Lieuwen, Timothy C.
    To combat carbon dioxide emissions, it is desirable to transition existing combustion systems to carbon-free fuels such as hydrogen and ammonia without negatively impacting air quality. However, quantitatively assessing air quality impacts of pollutants such as NOx is a nuanced process when comparing emissions across different fuels. Recently, the authors of this study published a separate paper showing that some standardized measurement approaches (i.e., measuring dried exhaust concentration) were inflating pollutant emissions by up to 40% for hydrogen combustion relative to natural gas. In this white paper, we extend this analysis to ammonia and cracked ammonia blends, showing that using concentration-based reporting approaches for comparing NOx from ammonia combustion is appropriate (less than a 3% effect), but can inflate apparent NOx emissions from fully cracked ammonia (i.e., an H2/N2 fuel blend) by 20%.
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    NOx Emissions from Hydrogen-Methane Fuel Blends
    (Georgia Institute of Technology, 2022-01) Douglas, Christopher M. ; Emerson, Benjamin L. ; Lieuwen, Timothy C. ; Martz, Tom ; Steele, Robert ; Noble, Bobby
    A variety of proposals are in place to utilize hydrogen (H2) as a green energy carrier which can be transported in pipelines and burned by a variety of stationary and mobile sources, such as power plants, heaters, and trucks. As a carbon-free fuel, hydrogen has the desirable property that its combustion releases no CO2. However, H2 combustion does generate NOx since, as noted above, NOx is formed when air is heated to high temperatures. This white paper shows that many studies could be interpreting their NOx emissions incorrectly by as much as 40% against high-hydrogen systems.
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    Hydrogen Utilization in the Electricity Sector: Opportunities, Issues, and Challenges
    (Georgia Institute of Technology, 2021-07) Lieuwen, Timothy C. ; Emerson, Benjamin L. ; Noble, Bobby ; Espinoza, Neva
    When the sun is shining and the wind is blowing, solar and wind energy are the lowest cost sources of electric power in the country. This energy can be used to directly power electrical devices, such as lighting for buildings or charging electric vehicles. It can also be stored in batteries for short term storage or can be used to make hydrogen, which can be stored or put in a pipeline for later use, including users that are a long distance away. On the other hand, natural gas fi red gas turbines are both the lowest cost non-intermittent power source, and the largest source of electric power in the US, at around 40%. Can they continue to evolve and be repurposed to utilize stored hydrogen for electric power?
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    Identification of High-Frequency Transverse Acoustic Modes In Multi-Nozzle Can Combustors
    (Georgia Institute of Technology, 2020-01) Kim, Jeongwon ; Gillman, Wesley ; Wu, David ; Emerson, Benjamin ; Acharya, Vishal ; Mckinney, Randal ; Isono, Mitsunori ; Saitoh, Toshihiko ; Lieuwen, Timothy C.
    High frequency thermoacoustic instabilities are problematic for lean-premixed gas turbines. Identifying which acoustic mode is being excited is important, in that it provides insight into potential mitigation measures, as well as input into mechanical stress/lifing calculations. However, the frequency spacing between modes becomes significantly narrower for high frequency instabilities in a can combustor. This makes it difficult to distinguish between the modes (e.g., the first transverse mode vs. a higher order axial/mixed mode) based upon frequency calculations alone, which inevitably have uncertainties in boundary conditions, temperature profiles, and combustion response. This paper presents a methodology to simultaneously identify the acoustic mode shapes in the axial and azimuthal directions from acoustic pressure measurements. Multiple high temperature pressure transducers, located at distinct axial and azimuthal positions, are flush mounted in the combustor wall. The measured pressure oscillations from each sensor are then used to reconstruct the pressure distributions by using a least squares method in conjunction with a solution of a three dimensional wave equation. In order to validate the methodology, finite element method (FEM) with estimated post-flame temperature is used to provide the candidate frequencies and corresponding mode shapes. The results demonstrate the reconstructed mode shapes and standing/spinning character of transverse waves, as well as the associated frequencies, both of which are consistent with the FEM predictions. Nodal line location was also extracted from the experimental data during the instabilities in the pressure data. It was found that the line was wandering at fixed location for one mode, whereas the line was rotating in one direction for the other mode. This paper details these experimental measurements and analysis methodologies for high frequency modal identification in self-excited can combustors.
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    Energy in the Information Age
    (Georgia Institute of Technology, 2016-09-06) Lieuwen, Timothy C.
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    Energy and Security in History, Technology, and Society
    ( 2015-02-06) Brown, Marilyn A. ; Lieuwen, Timothy C. ; Moreno-Cruz, Juan ; Stulberg, Adam ; Usselman, Steven W.
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    Towards a New Era of Gas?: Trends, Challenges, and Opportunities [Panel, part 1]
    (Georgia Institute of Technology, 2014-04-16) Stulberg, Adam ; Ladislaw, Sarah O. ; Suleymanov, Elin ; LeBlanc, Raoul ; Lieuwen, Timothy C. ; Kurfess, Thomas R.
    Moderator: Adam N. Stulberg ; Panel Discussion (Part 1): Towards a New Era of Gas?: Trends, Challenges, and Opportunities: Sarah O. Ladislaw, Director and Senior Fellow, Energy and National Security Program, Center for Strategic & International Studies ; Elin Suleymanov, Ambassador of the Republic of Azerbaijan to the United States of America ; Raoul LeBlanc, Managing Director, Global Gas, PFC Energy ; Timothy C. Lieuwen, Professor of Aerospace Engineering & Executive Director of the Strategic Energy Institute, Georgia Institute of Technology ; Thomas Kurfess, Professor and HUSCO/Ramirez Distinguished Chair In Fluid Power and Motion Control, The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology
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    Cross-flow dilution air jet studies
    (Georgia Institute of Technology, 2010-12-01) Seitzman, Jerry M. ; Lieuwen, Timothy C. ; Wilde, Ben ; Noble, Bobby
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    Turbulent flame speed measurements and modeling of syngas fuels
    (Georgia Institute of Technology, 2010-11-30) Seitzman, Jerry M. ; Lieuwen, Timothy C.