A STUDY ON EMISSION CHARACTERISTICS OF NH₃/DME FLAMES IN A FUEL STAGING COMBUSTOR

The combustion process of ammonia causes high NO_x emissions. In order to reduce NO_x emissions, the fuel staging strategy was applied in NH₃/dimethyl ether combustion. In this work, the emission characteristics of NH₃/DME flames were investigated in an experimental fuel staging combustor. It was found that the NO and NO₂ concentration in exhaust decreased when the fuel staging strategy was used. The maximum reduction rates of NO and NO₂ were 60.1% and 88.7%, respectively. NH₃ was almost completely consumed under single stage combustion, but it was emitted when fuel staging method was used. The concentration of NH₃ in exhaust increased with the increase of secondary NH₃ injection flowrate, while the trend of the NO concentrations was opposite. The emission concentrations of NO_x and NH₃ were observed to reach relatively low values (around 3 × 10⁻³) simultaneously at φ_pri = 0.85 when the thermal power of the combustor was 0.6 kW. The experimental results showed that the globally lean-locally lean two-stage combustion strategy has a promising application prospect in NO_x reduction. Then, the numerical study was conducted in the chemical reactor network (CRN) to further analyze the NO emission behaviors of NH₃/DME fuel staging combustion. It was showed that the CRN model captured the trend of NO emission accurately. The results of NO sensitivity analysis showed that the DME is more active than conventional hydrocarbons and has a significant promoting effect on NO production. The ROP analysis showed that NO was mainly generated through HNO pathway at the primary stage zone, and consumed through the reactions NH₂ + NO = N₂ + H₂O and NH₂ + NO = NNH + OH at the secondary stage zone.