Abstract:

Due to the low density and the high adiabatic combustion temperature of hydrogen fuel, issues such as poor fuel-air mixing and high localized thermal NO _x formation arise in the combustion chamber. To address these problems, a numerical simulation employing the GRI-Mech 3.0 mechanism combined with the FGM combustion model was conducted. And the effects of the equivalence ratios, the air tube diameters, the fuel tube diameters and the spoiler structures on the mixing characteristics and the combustion performance are considered. The results of the study indicate that an increase in the diameter of the air pipe is not conducive to the complete mixing of fuel and air. Furthermore, the NO emission increases by 13 times after the air tube diameter is tripled in the lean combustion condition with an equivalence ratio of 0.4. After the fuel pipe diameter increased from 0.20 mm to 0.65 mm, the hydrogen jet depth at each equivalence ratio decreased by more than 30%, the fuel-air mixing effect became worse, and the anchored flame turned into a lifting flame. Increasing the equivalence ratios raises flame temperatures and diminishes the effectiveness of NO _x control, particularly with smaller air or fuel tube diameters. The spoiler structure strengthens the premixing process of fuel and air, improves the temperature uniformity of the combustion chamber and reduces the NO _x generation. Among the structures studied, structure B exhibits superior mixing optimization and combustion characteristics.

Key words: hydrogen, micromix combustion, mixing, NO _x emissions, numerical simulation

摘要：

氢燃料由于密度小、绝热燃烧温度高，造成了燃烧室内燃空掺混困难和局部热力型NO _x 过高等问题。基于GRI-Mech 3.0机理，结合FGM燃烧模型对纯氢燃烧开展了数值模拟，考虑了当量比、微管空气管径、燃料管径、扰流结构对燃空混合特性和燃烧性能的影响。研究结果表明，空气管径的增大不利于燃空的充分混合，当量比为0.4的贫燃状态下，空气管径扩大三倍后NO排放量提高了13倍；燃料管径从0.20 mm增大至0.65 mm后，导致各当量比下氢气射流深度均降低30%以上，燃空混合效果变差，锚定火焰转变为抬升火焰；当量比的增大会使火焰温度升高，削弱了小空气管径或小燃料管径下NO _x 排放的控制效果；扰流结构强化了燃料与空气的预混过程，提高了燃烧室温度均匀度，降低了NO _x 的生成，且采用结构B时混合优化效果与基础燃烧特征更佳。

关键词: 氢, 微混燃烧, 混合, NO _x 排放, 数值模拟