Abstract:
The combustion process of ammonia causes high NO
x emissions. In order to reduce NO
x emissions, the fuel staging strategy was applied in NH
3/dimethyl ether combustion. In this work, the emission characteristics of NH
3/DME flames were investigated in an experimental fuel staging combustor. It was found that the NO and NO
2 concentration in exhaust decreased when the fuel staging strategy was used. The maximum reduction rates of NO and NO
2 were 60.1% and 88.7%, respectively. NH
3 was almost completely consumed under single stage combustion, but it was emitted when fuel staging method was used. The concentration of NH
3 in exhaust increased with the increase of secondary NH
3 injection flowrate, while the trend of the NO concentrations was opposite. The emission concentrations of NO
x and NH
3 were observed to reach relatively low values (around 3 × 10
−3) simultaneously at
φpri = 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 NH
3/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 NH
2 + NO = N
2 + H
2O and NH
2 + NO = NNH + OH at the secondary stage zone.