Abstract: In order to obtain the change rules between fuel-staged ratio and flue gas emission， based on the concepts of fuel-staged combustion， combined with numerical simulation and experimental research， the NO_x emission characteristics of axial fuel-staged combustion with CH4 as fuel were studied. In the fuel-staged chemical reaction network model， the effects of residence time and fuel-staged ratios on the NO_x emission were studied， and the reaction routes of NO_x were analyzed， and the effects of the blending performance of secondary fuel and flue gas on NO_x emission were analyzed by adjusting the ratio of flue gas involved. For a fuel-staged model burner， NO_x emissions at different fuel-staged ratios and at different secondary fuel flow rates were measured experimentally. The results showed that fuel-staged combustion could shorten the residence time of the flue gas in the high temperature region and restrained the generation of Thermal-NO. In the initial stage of the combustion in the reburning zone， the secondary fuel formed a reductive atmosphere with high-temperature flue gas， and the NO in the main combustion flue gas was reduced by NO reburning. In a certain total equivalence ratio condition， the increase of fuel-staged ratios decreased the NO_x emissions of the outlet and the proportion of NO₂ in the NO_x emissions increased. The low amount of flue gas mixed with the secondary fuel would form the local high temperature of the reburning zone， which led to the increase of NO_x emission.

Key words: Axial fuel-stage；Nitrogen oxides；Reaction route；Fuel-staged ratios

摘要： 为了获得燃料分级比例与烟气排放之间的变化规律，基于燃料分级概念，结合数值模拟和实验研究的手段对以CH4为燃料的轴向燃料分级燃烧中NO_x排放特性进行了研究。建立燃料分级化学反应器网络模型，研究了停留时间和燃料分级比例对NO_x排放的影响，对燃料分级燃烧中的NO_x反应途径进行了分析，并通过调节参与再燃的烟气比例分析了二级燃料与烟气的掺混性能对NO_x排放的影响。针对燃料分级模型燃烧器，实验测量了不同燃料分级比例和不同二级燃料流量下的NO_x排放。结果表明，燃料分级缩短了烟气在高温区的停留时间，抑制了热力型NO的生成；在再燃区燃烧反应初始阶段二级燃料与高温烟气形成还原性气氛，通过NO再燃还原了主燃烟气中的NO；在一定的总当量比工况下，燃料分级比例的增加降低了出口的NO_x排放，提高了NO_x排放中NO₂的比例。与二级燃料进行掺混反应的烟气量过少会形成再燃区的局部高温，导致NO_x排放增加。

关键词: 轴向燃料分级；氮氧化物；反应途径；燃料分级比例