Experimental and reaction mechanism study on laminar burning velocity and characteristics of OH/NH generation in ammonia co-combustion

Developing fuels without carbon, such as ammonia (NH 3 ), is crucial for achieving carbon reduction. Laminar burning velocity (LBV) is investigated, and distribution characteristics of OH and NH radicals are identified through planar laser-induced fluorescence. Rate of production of main free radicals and sensitivity analysis are also studied. The addition of NH 3 to CH 4 -air mixtures results in a decrease in the LBV, a rise in preheating zone height, a reduction in OH radical fluorescence intensity , and an enhancement in NH radical fluorescence intensity. Simulation reveals that the high NH 3 ratio enhance the negative impact of nitrogen-containing elementary reactions on LBV. The addition of NH 3 enhances the initial consumption of more OH via reaction R 248 : NH 2 + OH = NH + H 2 O , leading to increased NH production, and indicating a negative effect on LBV. The decrease in OH concentration is the main factor leading to a decrease in LBV. The reactions affecting the OH generation and consumption are R 39 : H + O 2 = O + OH and R 85 : OH + H 2 = H + H 2 O , respectively. The addition of NH 3 leads to a more significant reduction in R39. • The impact of NH 3 on the combustion characteristics of coal volatiles was studied. • The addition of NH 3 reduces the OH signal while increases the NH signal. • Primary reactions affecting LBV are H + O 2 = O + OH and H + CH 3 (+M) = CH 4 (+M). • H + O 2 = O + OH and OH + H 2 = H + H 2 O are the main reactions for OH generation and consumption.