Srujan Gubbi
(Advisor: Prof. Wenting Sun]
will propose a doctoral thesis entitled,
Study of NOx Chemistry in Ammonia Combustion
On
Friday, April 25 at 9:00 a.m.
Montgomery Knight Building 317
Abstract
The need for decarbonized energy has highlighted ammonia (NH3) as a hydrogen carrier and potential alternative fuel. However, using NH3 in combustion applications comes with other challenges, particularly high levels of NOx emissions due to the presence of fuel-bound nitrogen. Previous studies have proposed different strategies to reduce NOx emissions, such as flameless combustion and Rich-Quench-Lean (RQL). However, a majority of the effort has gone into computational modeling using existing NH3 kinetic models.
Even with these previous efforts, there are still knowledge gaps regarding NOx formation for NH3 combustion. First, it is still unknown what the fundamental floor on NOx emissions is. While staged combustion is an effective way to reduce NOx emissions for nitrogen-containing fuels, the design considerations that are required to achieve the lowest possible NOx emissions when burning NH3 still remain unknown. Second, no validated NH3 kinetic model currently exists, especially on NOx formation. This is particularly critical for ammonia combustion as modeling investigations on designing low-NOx combustors depend on reliable NOx models for NH3 combustion. Many kinetic models have been published and validated using flow reactor and shock tube experiments. Still, significant discrepancies exist between kinetic models in terms of their prediction of NOx chemistry, specifically in flames. There is also a lack of experimental data on NOx measurement in flames for kinetic model validation purposes.
The work proposed here aims to expand the current knowledge of NOx chemistry for NH3 combustion using combined modeling and experimental approaches. The modeling component will use reactor network modeling to determine the theoretical minimum NOx emissions from NH3 combustion for a staged combustion configuration using existing kinetic models. An optimization will be done to determine values for design variables that will achieve this minimum, and the sensitivity of the minimum to firing temperature, pressure, residence time, and cracking fraction will also be explored. The experimental component will employ Laser-Induced Fluorescence (LIF) and Rayleigh scattering in NH3 flames in a counterflow burner and Hencken Burner to conduct measurements on key species. The measured species from LIF will be NO, NH, and NH2 which are critical for NOx chemistry validation. This work will create unique datasets that can be used for the validation of NH3 kinetic models. Kinetic analyses will be done using existing NH3 kinetic models, providing direction for the improvement of these models using the new data collected in this study.
Committee
- Prof. Wenting Sun – School of Aerospace Engineering (advisor)
- Prof. Tim Lieuwen – School of Aerospace Engineering
- Dr. Ben Emerson – School of Aerospace Engineering