Preprint / Version 2

Optical Characterization of Cellular Instabilities in Spherically Expanding Ammonia-Hydrogen Flames




ammonia, hydrogen, flame, combustion, instabilities


Ammonia (NH3) and hydrogen (H2) are promising zero-carbon fuels that face numerous technical challenges. Some of the potential issues may be mitigated if they are used together as blends and fundamental combustion studies can provide insight into how these fuels interact. This study aims at improving the understanding of the formation of cellular instabilities as NH3-H2 fractions vary at various equivalence ratios. Premixed NH3-H2 blends are ignited in a constant volume combustion chamber (CVCC) with optical access and Schlieren images of the resulting spherically expanding flames are recorded using a high-speed camera. The images are processed to automatically determine the length of cracks within the spherical flame and the evolution of instabilities is analyzed using the length of cracks. The mole fraction of H2 in the H2/NH3 blend is varied between 0% and 50% at increments of 10% and the equivalence ratio is varied between 0.5, 0.7, 0.9, 1.0, 1.1, and 1.3 for each mole fraction. It is observed that instabilities appear at shorter flame radii as the fraction of H2 is increased and the total crack length is also higher. However, this trend diminishes as the equivalence ratio increases and few to no cracks are observed for the richer conditions at high H2 fractions.


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2023-05-26 — Updated on 2023-05-30