Session: 04-07 Ammonia Combustion I

Paper Number: 152740

A Study on Combustion Characteristics of Radial Inward Flow Porous Media Burners for Ammonia-Hydrogen Flames 

The present study investigates the potential of porous media burners to improve the combustion characteristics of unconventional fuels, with a focus on ammonia (NH$_3$). The unique heat recirculation characteristics of porous media extend the flammability limits of premixed flames, counteracting the inherently poor combustion properties of NH$_3$. The present study establishes a radial inward flow porous media burner with dynamic flame stabilization,  featuring a compact ceramic foam made of silicon carbide. The foam's Voronoi-based lattice porous structure includes a continuously graded topology, with a linear pore density varying from 10 to 20 pores per inch from the inner to outer radial direction. The burner flammability limits were evaluated with up to 30\% hydrogen $(H_{2})$ by volume added to the fuel stream. The stability range for pure NH$_3$ operation was $0.8 \leq\phi\leq 1.3$, which was extended to $0.55 \leq\phi\leq 1.5$ for 30/70 H$_2$/NH$_3$ mixtures. Infrared radiometry was employed to determine the solid matrix temperature using a narrow band-pass filter to avoid interference of gaseous species. The solid temperatures in the preheat region and the combustion zone revealed the flame front propagation behavior as influenced by variations in the mixture equivalence ratio, H$_2$/NH$_3$ ratio, and the mass flow rate, highlighting the geometric advantages provided by the radial porous media burner. The measured exhaust gas temperatures and the ceramic foam temperatures were correlated to provide insight into flame dynamics. Emissions of NO, along with NH$_3$ and H$_2$ slip, were analyzed in various mixture compositions and equivalence ratios. Conditions which minimized NO emissions included a) near lean-limit NH$_3$/H$_2$ combustion, b) rich conditions of $\phi\geq 1.2$, and c) pure NH$_3$ at near-stoichiometric conditions with low combustion temperature due to low mass flux. The measured pollutant emissions were compared with a perfectly stirred reactor model yielding good agreement.

Presenting Author: Joseph Lefkowitz Technion-IIT

Presenting Author Biography: Joseph Lefkowitz is an Associate Professor at the Technion – Israel Institute of Technology in the Department of Aerospace Engineering. He earned his PhD from Princeton University and completed postdoctoral research at the U.S. Air Force Research Laboratory. His research focuses on combustion, propulsion, and sustainable aviation fuels (SAFs), with expertise in ignition optimization and diagnostics for various fuel types. Dr. Lefkowitz leads the Combustion and Diagnostics Laboratory at Technion and has published extensively on high-speed ignition and alternative fuel systems.

Authors:

Guguloth Mahesh Nayak Technion-IIT
Beni Cukurel Technion-IIT
Joseph K. Lefkowitz Technion-IIT