Modeling nitrogen species from ammonia reciprocating engine combustion in temperature-equivalence ratio space
William F. Northrop
Abstract
This paper explores nitrogen species formation in temperature (T)-equivalence ratio (ϕ) space under internal combustion engine-relevant conditions using zero-dimensional modeling. The analysis reveals that N2O and NO are formed in a much larger region of ϕ-T space than in hydrocarbon combustion due to fuel chemical pathways. N2O is formed over a large range of ϕ, primarily in low temperature regions that have significant levels of unburned NH3. NO is formed over a large, high temperature, lean region. Further analysis shows that even when mixing burned gas with unburned NH3 from engine crevices, N2O is reduced to low levels in the expansion stroke after initially increasing due to the thermal de-NOx mechanism. This indicates that N2O emissions measured from premixed engine combustion are likely from quenching near cold surfaces.