ABSTRACT

This paper presents the effect of CO₂ and N₂ dilution in the oxidizer stream on combustion and emission characteristics in a flameless combustor operating with kerosene and biodiesel as a fuel. The thermal input is varied from 30 kW (7.5 MW/m³) – 53 kW (13.3 MW/m³) and inlet air temperature are varied from 300 K to 800 K. CO₂/N₂ are added to dilute the oxidizer stream in a proportion of 15% of total air volume to reduce the O₂ concentration in the air stream. Reacting and non-reacting flow simulations show that the flow field improves significantly as both the flow velocity and temperature distributions become uniform. Distribution of the reactant dilution ratio becomes more uniform and a maximum value of R_dil = 4.89 is achieved for 30 kW conditions. The reduced O₂ concentration in the oxidizer results in enhanced dilution of fresh air-fuel mixture thereby enables uniform temperature and flow field. For the air preheating case, CO₂ dilution does not affect the velocity and thermal fields significantly. The measured CO emissions are marginally increased due to CO₂ dilution; however, NO_x emissions are significantly reduced. N₂ dilution results in increased levels of NO_x, contrary to the perception of the inert role of N₂ addition even though the combustor operating temperatures are lower than 1800 K. The measurements of acoustic pressure emissions show a sharp decrease during flameless combustion mode.

摘要

本文介绍了氧化剂流中的 CO ₂和 N ₂稀释对使用煤油和生物柴油作为燃料的无焰燃烧器的燃烧和排放特性的影响。热输入从 30 kW (7.5 MW/m ³ ) 到 53 kW (13.3 MW/m ³ ) 不等，入口空气温度从 300 K 到 800 K 不等。添加 CO ₂ /N ₂以稀释氧化剂流占总风量的 15%，以减少 O ₂气流中的浓度。反应和非反应流动模拟表明，随着流速和温度分布变得均匀，流场显着改善。 反应物稀释比的分布变得更加均匀，并且在 30 kW 条件下实现了R _dil = 4.89的最大值。氧化剂中O ₂浓度的降低导致新鲜空气-燃料混合物的稀释增强，从而实现了均匀的温度和流场。对于空气预热情况，CO ₂稀释不会显着影响速度和热场。由于 CO ₂稀释，测得的 CO 排放量略有增加；然而，_NOx排放量显着减少。N ₂稀释导致NO _{x水平增加，这与添加N 2}的惰性作用相反，即使燃烧器操作温度低于1800 K。声压排放的测量显示在无焰燃烧模式期间急剧下降。