Ignition characteristics of hydrogen-enriched ammonia/air mixtures

Abstract

Ammonia is an attractive hydrogen carrier and potential fuel which could play a role in decarbonizing process heat, power or transport applications. However, the combustion properties of ammonia are disadvantageous for many technical processes. Hydrogen addition has been shown to mitigate this challenge by increasing the laminar burning velocity and extending the lean blow-off limit. In this work, the ignition characteristics of hydrogen enriched ammonia/air mixtures are investigated experimentally. A capacitive discharge is used to ignite the mixture. The effects of an increasing share of hydrogen in the fuel are a drastic decrease in ignition energy as well as an increase in explosion pressure and the rate of pressure rise. Further, schlieren imaging was employed to study the structure and evolution of the flame kernel shortly after ignition. Due to the high discharge energy necessary to ignite ammonia/air, the flame kernel evolution is dominated by the discharge.