燃料掺混方式对天然气柔和燃烧器燃烧性能的影响研究

燃气轮机在更高参数下的低污染排放限制和宽工况范围稳定运行的需求,对燃烧室燃烧提出了新的要求。柔和燃烧作为一种新型燃烧技术,具有燃烧稳定和污染物排放低的优势。高速射流引射掺混是实现柔和燃烧所需条件的一种可行方式。本文主要研究不同燃料掺混方式对柔和燃烧器污染物排放和稳定工作范围的影响。在前期工作基础上设计了可实现燃料不同掺混方式的天然气柔和燃烧器。在常压条件下,通过实验研究了不同当量比、不同燃料/空气掺混方式下天然气柔和燃烧器的污染物排放,并研究了不同掺混方式对燃烧贫燃极限的影响,通过OH~*自发荧光、OH平面激光诱导荧光测量和数值模拟对反应区和流场结构进行了观察和分析。实验结果表明,在相同当量比下,全预混模式下的NO_x排放最低,全预混模式下稳定燃烧的贫熄火当量比为0.57;扩散模式下NO_x排放相对高,但贫熄火当量比可低至0.15,燃烧稳定范围更宽;混合模式下污染物排放水平介于预混和扩散模式之间;非预混模式下较好的贫燃火焰稳定性得益于燃烧室头部扩散燃料周围形成的低速稳定反应区。

Investigation of the Effect of Fuel Mixing Mode on the Combustion Characteristics of A Natural Gas MILD Combustor

To reduce pollutant emission and to widen stable operating range for gas turbine with advanced parameter, we turned to MILD combustion featured by low pollutant emission and good stability. High momentum jet injection was used to create the flow field for MILD combustion, and fuel mixing strategy was investigated to broaden the range for stable combustion. A natural gas MILD combustor capable of changing fuel mixing mode was designed. Under the atmospheric condition, The influence of fuel/air mixing mode and equivalence ratio on the combustion characteristics have been investigated, the optical combustion diagnostics and CFD was taken to analyze the concerned reaction zone. It was shown that for the premix mode, the equivalence ratio at lean blow off (^LB0 ) was 0. 57 and the NOx emission reached the minimum value, while for the diffusion mode, ^LB0 was shifted to 0. 15 ,whereas the NOx emission exceeded the former level, and the NOx emission for the transition mode was between them. It also turned out the good flame stabilization for the diffusion and transition mode was dependent on the low speed reaction zone around the diffusion fuel nozzle.