多点喷射贫预混喷嘴流场及排放特性研究

Flowfield and Emission Characteristics of Lean Premixed Injector with Multi-Point Injection

关键词:  燃气轮机  低污染燃烧室  多点喷射  贫预混喷嘴  预混不均匀度  排放特性

Key words:  Gas turbine  Low emission combustor  Multi-point injection  Lean premixed injector  Spatial mixing variance  Emission characteristics

摘要:

基于燃料喷射孔与旋流器中空叶片相耦合的发展趋势和避免贫预混喷嘴发生回火和自燃，本文提出了一种新型的带收敛出口、壁面开冷却孔且中空叶片叶背开喷射孔的多点喷射贫预混喷嘴，试验研究了其流场和污染排放特性，并采用数值计算方法对流场和燃料/空气混合特性进行了补充研究。结果表明：主回流区脱离喷嘴出口一段距离，有利于产生脱体火焰而防止发生自燃和回火，且本文喷嘴出口温度监测结果也证实了在喷嘴内未发生自燃和回火；不同压力状态下喷嘴出口截面混合不均匀度SMV（Spatial Mixing Variance）均在4.7%左右，满足低污染燃烧室SMV低于5%的要求；并且污染物排放试验结果表明，贫预混喷嘴能同时满足NO_x和CO排放要求（@15%O₂）的Φ_dome范围较宽，为0.65~0.82，能减少其应用在全环燃烧室的分级数，另外当Φ_dome低于0.70时，贫预混喷嘴的NO_x排放低于1×10^-5（@15%O₂）。本文提出的新型贫预混喷嘴能满足燃气轮机低污染排放要求。

Abstract:

Based on the development trend of incorporating fuel holes into hollow swirler-vanes and avoiding the auto-ignition and flashback of lean premixed injectors， an original lean premixed injector with multi-point injection and the convergent outlet was proposed. Its fuel holes are located on the swirler-vanes basin and there are a number of cooling holes in its premixing section. The flowfields and emission characteristics of the lean premixed injector were investigated by experiments， and supplementary study on flowfields and fuel/air premixing uniformities were carried out by numerical simulations with the verification of experimental results. The results show that： the main recirculation zone （MRZ） is separated from the injector outlet for a certain distance， which is conducive to the generation of detached flame and avoid the risk of auto-ignition and flashback. The monitoring temperature results of the injector outlet in this paper also confirm that there is no spontaneous combustion and tempering in the injector. The spatial mixing variance （SMV） values at the outlet of the nozzle are all about 4.7% under different pressure conditions， which meets the requirement that SMV of low emission combustor should be less than 5%. The emissions experiment results show that dome equivalence ratio （Φ_dome） of the lean premixed injector， at which its NO_x and CO emissions （@15%O₂） could both meet the emission requirements， ranges from 0.65 to 0.82， and its wide range of Φ_dome can reduce the number of stages used in full ring combustor. In addition， when Φ_dome is lower than 0.70， the lean premixed injector is capable of achieving NO_x emissions below 1.0×10^-5 （@15%O₂）. Therefore， the original lean premixed injector proposed in this paper could meet the stringent emission standards of industrial gas turbine.