Session: 04-24 Combustion - Modeling II

Submission Number: 179313

Modeling and Design of a Counterflow Burner for Ammonia-Hydrogen Flames Extinction Limits Under High-Pressure Conditions 

The counterflow burner is a well-established configuration used to study fundamental combustion phenomena, mainly the interaction between chemical reactions and transport processes under controlled conditions. This study focuses on the modeling and design of a counterflow burner to investigate the extinction limits, flame structure, and species distribution of ammonia/hydrogen blend flames at both ambient and high-pressure conditions relevant to aviation gas turbine applications. Ammonia is emerging as a promising carbon-free fuel and hydrogen carrier due to its high hydrogen content, limited flammability range, and compatibility with existing fuel infrastructure. However, challenges such as low burning velocity, high ignition energy, and the formation of nitrogen oxides (NOx) demand detailed experimental and numerical investigations to enable its practical implementation. Blending ammonia with hydrogen enhances its reactivity, improves ignition characteristics, and reduces unburned ammonia slip, making it suitable for high-performance combustion systems. The designed counterflow burner consists of two vertically opposed concentric tubes, with the top tube supplying oxidizer and the bottom tube delivering the ammonia/hydrogen fuel mixture. A nitrogen sheath flow is introduced to prevent secondary combustion and ensure stable flame formation at the stagnation plane. Each tube outlet incorporates a honeycomb and three 200-mesh stainless-steel screens to ensure uniform flow distribution and minimize turbulence. The Reynolds number for both the fuel and oxidizer streams was maintained at a low value to ensure laminar, axisymmetric flow conditions at the nozzle exits. Flow velocities and nozzle diameters were selected to achieve comparable Reynolds numbers on each side, providing a stable stagnation plane and distinct strain rate for extinction studies. Cantera simulations were used to estimate flow rates, temperature distributions, and initial flame locations between the two opposing jets. The entire burner assembly is constructed from 316 stainless steel to withstand ammonia corrosion and elevated pressures, with the wall thickness and flange dimensions determined using ASME high-pressure vessel codes. Computational Fluid Dynamics (CFD) simulations were conducted using ANSYS Fluent to investigate the laminar flow distribution, velocity gradients, and mixing characteristics between the opposing jets. Future work will integrate a high-pressure vessel with the burner to experimentally measure flame extinction strain rates, species concentrations, and NOx emissions using laser absorption spectroscopy. This will provide critical insights into the viability of ammonia/hydrogen blends as next-generation carbon-free fuels for gas turbine and aerospace propulsion applications.

Presenting Author: Shahzad Bobi University of Central Florida

Presenting Author Biography: I am a graduate student at the University of Central Florida. My research focuses on internal combustion engines and alternative fuels, particularly ammonia and hydrogen, to achieve cleaner and more sustainable combustion. My goal is to contribute to advancements in clean energy technologies that benefit both combustion industry and humanity

Authors:

Shahzad Bobi University of Central Florida
Priyankar Garai University of Central Florida
Ramees K. Rahman University of Central Florida
Oli M. Valenzuela University Of Central Florida
Subith Vasu University of Central Florida