Conceptual Design and Simulation of an Ammonia-Cracking Combustor

Hydrogen has long been at the center of attention as the fuel of the future to achieve carbon-free gas turbine power generation. This choice seems obvious at first glance as hydrogen is very energy-dense on a unit-mass basis and its combustion produces only water as its primary emission. However, complications with hydrogen’s production and liquid-phase storage requirements and low volumetric energy density currently make it practically and economically more inconvenient to use as a combustion fuel than conventional hydrocarbons. Fortunately, ammonia fuel addresses these specific complications while fitting the criteria of being a carbon-free fuel, albeit while ignoring the issue of ammonia’s toxicity. Unfortunately, ammonia combustion has its own challenges with very low flammability and high NOx emissions that must be addressed in order for it to be a viable replacement for pure hydrogen. This presentation will show CFD simulations of an aero-engine gas turbine combustor designed for the NASA CarbonLess Electric AviatioN (CLEAN) project that utilizes detailed combustion chemistry and a one-step surface reaction for ammonia decomposition that addresses the low flammability and high NOx issues in one package.