Session: 03-04 Hybrid-Electric and Ammonia-Based Propulsion Concepts for Sustainable Aviation

Submission Number: 179380

Numerical Investigation of Extinction Strain Rates in Ammonia-Hydrogen Counterflow Diffusion Flames Under High-Pressure Conditions 

Ammonia is increasingly being recognized as a potential zero-carbon fuel for aviation due to its high hydrogen content and well-established global production infrastructure. However, its low reactivity, toxicity, and tendency to produce high nitrogen oxide (NOx) emissions pose significant challenges for practical implementation. Blending ammonia with hydrogen offers a promising route to overcome these limitations by enhancing flame stability and improving combustion efficiency while maintaining carbon-free operation. This study investigates the behavior of ammonia-hydrogen diffusion flames under elevated pressures, focusing particularly on the extinction strain rate, which defines the maximum aerodynamic strain a flame can withstand before quenching. Counterflow diffusion flame simulations were conducted using Cantera while utilizing the detailed Glarborg (2018) [RK1] , C3mech v4 (2025), Szanthoffer et al (2025), Jian et al (2024) and the UCF (2024) chemical kinetic mechanism to examine ammonia-hydrogen mixtures of varying compositions across a range of pressures, specifically 1 bar, 20 bar and 40 bar. The results show that increasing pressure consistently enhances the extinction strain rate and flame stability, indicating that flames become more resistant to aerodynamic stretching as operating pressure rises. Similarly, enriching ammonia with hydrogen substantially strengthens the flame, as hydrogen addition accelerates radical generation and heat release, leading to more compact and resilient flame zones. In contrast, pure ammonia flames exhibit low stability and weaker temperature profiles, highlighting the difficulty of sustaining combustion without hydrogen addition. To validate the computational trends, a vertical counterflow burner is being developed, featuring concentric nozzles for the fuel and oxidizer at opposing sides, honeycombs/screens to straighten the flow, and inert co-flows to ensure symmetric, buoyancy-free operation at pressures up to 30 bar. Additionally, reaction pathway analysis and sensitivity analysis will also be conducted  to identify the important reactions and key species that govern extinction behavior, providing a better understanding of the chemical kinetic pathways influencing flame stability. Together, these efforts provide valuable insight into ammonia-hydrogen flame behavior under high-pressure conditions and support the development of cleaner, more efficient combustor designs for next-generation low-emission aviation systems.

Presenting Author: Priyankar Garai University of Central Florida (UCF)

Presenting Author Biography: I am currently pursuing my PhD in Aerospace Engineering at University of Central Florida (UCF), with Dr. Subith Vasu Sumathi as my PhD advisor. I work at the CATER (Center for Advanced Turbomachinery and Energy Research) Lab at UCF under Dr. Vasu's supervision, where the research is primarily focused on Turbomachinery and Associated Technologies for Power Generation, Aviation and Space Propulsion. I previously graduated with my bachelors from the Indian Institute of Technology, Kanpur (IITK), India, and with my masters from Texas A&M University, College Station (TAMU), both in Aerospace Engineering. My current work is with Ammonia as a fuel where we are trying to exploit the benefits of Ammonia as a green fuel and a zero-carbon fuel in order to potentially replace the current Jet fuels which are non-biodegradable and hence unsustainable for the future.

Authors:

Priyankar Garai University of Central Florida (UCF)
Shahzad Bobi University of Central Florida (UCF)
Ritesh Ghorpade University of Central Florida (UCF)
Ramees K. Rahman University of Central Florida
Subith S. Vasu University of Central Florida (UCF)