ABSTRACT

This paper presents experimental results of the effects of CO₂ and H₂O dilution on CH₄-air flames enriched by oxygen. The study focuses on pollutant emissions, flame stability through the determination of liftoff heights and flow fields by LDV measurements. Different parameters of the burner are studied such as the swirl number, the global equivalence ratio, and the fractions of O₂, H₂O, and CO₂ in the mixture. The fraction of diluents varies from 0% to 20%, O₂ enrichment from 21% to 30% (in vol.), and the swirl number from 0.8 to 1.4. The experiments are carried out on a coaxial swirled burner placed in a vertical combustion chamber. The flame is visualized by the chemiluminescence technique on OH* in order to locate the flame front. Measurements of combustion products such as NOx, CO, and CO₂ are done using a HORIBA PG250 multi-gas analyzer. Flow fields are measured by LDV measurement for the longitudinal velocity component and its fluctuations. Results show that the CO₂ and H₂O dilution influences significantly the flame characteristics. With dilution the liftoff height increases but the flame remains stabilized. With O₂ enrichment the liftoff height decreases and flame stability is enhanced. If we therefore want to dilute more, we should enrich with oxygen. The increase of dilution rate induces a decrease in NOx emission and exhaust gas temperature and an increase in CO emissions. LDV measurements showed the longitudinal velocity distribution of flow and its fluctuations in reactive and non-reactive conditions. Note that the presence of the flame induces an increase in the longitudinal velocity downstream of the flow due to the expansion of gases.

摘要

本文介绍了CO ₂和H ₂ O稀释对富氧CH ₄空气火焰影响的实验结果。该研究着重于污染物排放，火焰稳定性，其通过LDV测量确定起升高度和流场。研究了燃烧器的不同参数，例如旋流数，整体当量比以及混合物中O ₂，H ₂ O和CO ₂的分数。稀释剂的分数从0％到20％O ₂富集度从21％增至30％（以体积计），涡旋数从0.8增至1.4。在放置在垂直燃烧室中的同轴涡旋燃烧器上进行实验。通过化学发光技术在OH *上可视化火焰，以便定位火焰前缘。使用HORIBA PG250多气体分析仪对燃烧产物（例如NOx，CO和CO _2）进行测量。通过LDV测量可测量流场的纵向速度分量及其波动。结果表明，CO ₂和H ₂ O稀释显着影响火焰特性。随着稀释，剥离高度增加，但是火焰保持稳定。与O ₂富集，提升高度降低，火焰稳定性增强。因此，如果我们想稀释更多，我们应该富含氧气。稀释率的增加导致NOx排放和废气温度的降低以及CO排放的增加。LDV测量显示在反应和非反应条件下，流体的纵向速度分布及其波动。注意，由于气体的膨胀，火焰的存在会导致气流下游的纵向速度增加。