Properties of Nonpremixed Ammonia-substituted Hydrogen-air Flames

The extinction and nitrogen oxide (NOx) emissions of nonpremixed ammonia (NH3)-hydrogen (H-2)-air flames were experimentally studied to evaluate the potential of partial NH3 substitution to improve the safety of H-2 use and provide a database of nonpremixed NH3-substituted H-2 -air flames. Considering coflow nonpremixed NH3-H-2-air flames at normal temperature and pressure for a wide range of fuel and coflow air injection velocities and the extent of NH3 substitution, the effects of NH3 substitution and fuel and air injection velocities on the combustion stability (extinction) limits and NOx, emissions of H-2 -air flames were investigated. Results show reduction of stability limits with NH3 substitution, supporting the potential of NH3 as an effective, green (i.e., carbon-free) additive in H-2 -air flames. The NOx, emission index (EINox) increases with enhanced NH3 substitution in general. For a given air injection velocity, EINOx), decreases and then increases with increasing fuel injection velocities.