低气压条件下甲烷预混燃烧CO和NO生成机理研究

Study on Formation Mechanisms of CO and NO in Methane Premixed Combustion at Low Air Pressure

为研究低气压条件对甲烷预混燃烧中CO和NO_(x)生成特性与生成路径的影响,采用Chemkin软件进行详细数值模拟研究。通过采用Python语言自编程序调用最新光谱数据计算普朗克平均吸收系数,并导入Chemkin软件中来提升辐射传热的计算精准度。结果表明:采用Konnov0.6化学反应机理与所提出的辐射模型中普朗克平均吸收系数计算方法可以准确预测低气压条件下甲烷燃烧的温度、NO和OH质量浓度分布;随着气压的降低,甲烷与空气预混燃烧时炉膛前部温度逐渐降低,而炉膛后部温度逐渐增加;气压降低导致CO生成速率增加和消耗速率减小,两者共同作用导致CO生成量增加和燃尽率降低;甲烷与空气预混燃烧生成的NO主要来自快速型和NNH型,且快速型和NNH型路径的贡献随着气压降低略有增加。

In order to study the influence of low air pressure conditions on the formation characteristics and pathway of CO and NO_(x) in methane premixed combustion,the detailed numerical simulation was carried out by using Chemkin software.According to the latest spectral data used by the Python language self-programmed program,the Planck average absorption coefficient was calculated and imported into Chemkin software to improve the calculation accuracy of radiation heat transfer.Results show that the combustion temperature of methane,concentration distributions of NO and OH at low air pressure can be accurately predicted by using Konnov 0.6 mechanism and the Planck average absorption coefficient calculation method in the radiation model.In addition,with the decrease of air pressure,the temperature in the front of the premixed combustion furnace decreases while that in the back increases gradually.The decrease of air pressure leads to the increase of CO formation rate and decrease of CO consumption rate,resulting in the increase of CO production and decrease of burn-out rate.The NO produced by the premixed combustion of methane and air was mainly from prompt-NO and NNH-NO,and the contribution of the prompt-NO and NNH-NO increases slightly with the decrease of air pressure.