Session: 04-29 Emissions Hydrogen/Ammonia II

Paper Number: 153268

Reducing NOx Emissions in Ammonia Combustors 

Ammonia continues to attract growing interest as a carbon-neutral replacement fuel, motivating numerous research efforts toward understanding fundamental ammonia combustion characteristics.  A major challenge for the use of ammonia is the development of combustor technologies for mitigating potentially high NOx emissions from the fuel-bound nitrogen chemical pathways to acceptable levels.  Our work focuses on a staged RQL combustor architecture for minimizing the NOx levels through burning fuel-rich in the primary stage to form combustion products containing significant levels of hydrogen in addition to nitrogen and water with minimal NOx formation.  The subsequent quench and burnout stages of the combustor must then quickly burn residual hydrogen with flame-temperatures moderated by nitrogen and water forming in the first stage.  Chemical Reactor Network modeling was used to understand and identify optimal stoichiometry and residence times in each stage for minimizing NOx and to quantify pressure and temperature effects.  Reducing the overall NOx emissions requires relatively long residence times in the primary stage to achieve near equilibrium NO levels due to kinetically controlling processes.  For conditions relevant to gas turbines (e.g., 35 atm), our work indicates that NOx emissions below 30 ppm are theoretically achievable in a staged RQL combustor architecture.  However, these emission predictions significantly depend on the accuracies of currently available chemical kinetic mechanisms which have not been extensively validated under elevated pressure and temperature conditions relevant to gas turbines.

Presenting Author: Paul Papas RTX Technology Research Center

Presenting Author Biography: Dr. Paul Papas received a B.S. in Aerospace Engineering from the Georgia Institute of Technology, M.A. from Princeton University, and Ph.D. in Aerospace and Mechanical Engineering from Princeton University in 1994. From 1994-96, he was a National Research Council Fellow at the US Naval Research Laboratory. From 1996-2004, he was a Senior Lecturer at the École Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland, and an Associate Professor at the Colorado School of Mines (Colorado, USA) from 2004-2010. Currently, Dr. Papas is a Technical Fellow of Combustion & Propulsion Technology at the RTX Technology Research Center, known formerly as United Technologies Research Center (Connecticut USA). Dr. Papas is a Fellow of the Combustion Institute, an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA), Past Chair of the Executive Board for the Eastern States Section of the Combustion Institute (ESSCI), Chair of the US Sections Board of Directors of the Combustion Institute (USSCI), and member of the Connecticut Academy of Science and Engineering (CASE). He has over 100 publications, patents, and conference papers in combustion and areas related to aviation sustainability, including propulsion, alternative fuels, combustion dynamics and instabilities, extinction, material flammability, fuel oxidation kinetics, and fire safety.

Authors:

Satyendra Rana University of Connecticut
Paul Papas RTX Technology Research Center
Lance L. Smith RTX Technology Research Center
Chih-Jen Sung University of Connecticut