天然气燃料轴向分级预混燃烧特性研究

低NOx排放是燃气轮机燃烧室的重要性能指标,面对燃烧室出口温度不断增加的趋势,新型燃烧技术探索应用成为必然。燃料轴向分级(Axial Fuel Staging,AFS)燃烧作为一项可行技术方案已在各燃机厂商的最先进燃气轮机燃烧室上获得应用,其主要通过降低高温烟气有效停留时间和低氧浓度燃烧来实现低NOx排放。基于Chemkin平台建立轴向分级预混燃烧室化学网络模型,针对1 973 K燃烧室,研究二级负荷比例、当量比和停留时间对NOx/CO排放的影响规律,对比分析主燃区高温烟气与二级未燃预混气掺混特征的影响,获得AFS燃烧的污染物排放特性和关键影响因素。同时,在贫预混燃烧器上,设计二级喷射段,实验研究二级火焰结构、污染物排放等燃烧特性。结果表明,相比于常规贫预混燃烧,AFS燃烧在高温区体现出很好的低NOx优势,且能拓宽低NOx工况范围,其中主燃区温度、二级当量比和停留时间匹配特征、主燃区高温烟气与二级预混气掺混性能等是关键。

Investigations of Combustion Characteristics of a Natural Gas Axial Fuel Staging Burner for Gas Turbine Application

With the objective of low NOx emission of gas turbines of the increased trend of combustion temperatures, investigating a new technology becomes inevitable. Axial fuel staging ( AFS) combustion technology has been applied to the most advanced gas turbine combustors,mainly by reducing exhaust gas residence time and oxygen concentration. Based on the Chemkin, a chemical model of axial fuel staging combustion with 1 973 K combustion temperature was established, studying the effects of secondary load ratio, secondary equivalent ratio, secondary residence time and mixing between secondary unburned gas and the high temperature exhaust gas of main chamber on NOx//CO emissions. At the same time, based on the axial fuel staging combustion model burner, the secondary flame structure and characteristics of emissions was experimentally studied. The results show that AFS combustion has the advantage of low NOx with high combustion temperature and broadening the load range. The main chamber temperature, secondary equivalent ratio, split of residence time and the mixing between secondary unburned premixed gas and exhaust gas of main chamber are the key to reduce the NOx emission in the axial staging combustion.