Predictions of NO and CO emissions in ammonia/methane/air combustion by LES using a non-adiabatic flamelet generated manifold

A large-eddy simulation (LES) employing a non-adiabatic flamelet generated manifold approach, which can account for the effects of heat losses due to radiation and cold walls, is applied to NH3/CH4/air combustion fields generated by a swirl burner, and the formation mechanisms of NO and CO for ammonia combustion are investigated in detail. The amounts of NO and CO emissions for various equivalence ratios, are compared with those predicted by LES employing the conventional adiabatic flamelet generated manifold approach and measured in the bespoke experiments. The results show that the amounts of NO and CO emissions predicted by the large-eddy simulations with the non-adiabatic flamelet generated manifold approach agree well with the experiments much better than the ones with the adiabatic flamelet generated manifold approach. This is because the NO and CO reactions for NH3/CH4/air combustion are quite susceptible to H and OH radicals’ concentrations and gas temperature. This suggests that it is essential to take into account the effects of various heat losses caused by radiation and cold walls in predicting the NO and CO emissions for the combustion of ammonia as a primary fuel.