基于化学反应器网络模型法的预混气组分对NOx反应路径影响研究

Effects of Premixed Gas Components on NOx Pathways Based on Chemical Reactor Network Model

关键词:  低排放燃烧室  预混气组分  反应路径  化学反应器网格模型法  绝热火焰温度

Key words:  Low emission combustor  Premixed gas components  Pathway  Chemical reactor network model method  Adiabatic flame temperature

摘要:

为探究预混气组分对不同反应路径下NO_x生成影响，针对高压射流反应器，基于CFD流场特征，构建优化了单PSR（Perfectly-stirred reactor），2PSR，3PSR以及PSR+PFR（Plug flow reactor）四种CRN（Chemical reactor network）模型。在贫预混燃烧条件下，研究了纯CH₄及其混合气燃烧时不同反应路径下NO_x的生成情况，得出了燃烧室内不同反应区域每条反应路径NO_x的生成量。结果表明，纯CH₄燃烧产生的NO_x主要来自于热力型、快速型和N₂O-中间体型三条反应路径。绝热火焰温度的提高主要促进了热力型和N₂O-中间体型NO_x的生成。随着CH₄或CO中加入的H₂摩尔分数的增加，NO_x排放总量降低，快速型NO_x生成速率降低，特别是火焰刷区。另外，混合气中CO摩尔分数的增加会导致NO_x生成量增多。

Abstract:

To investigate the effects of premix gas components on NO_x generation under different pathways， four chemical reactor network models， namely single PSR（Perfectly-stirred reactor）， 2PSR， 3PSR and PSR+PFR， were constructed and optimized based on the characteristics of CFD flow field in high-pressure jet stirred reactor. Under the condition of lean premix combustion， the NO_x generation of pure CH₄ and its mixture in different pathways were studied， and the NO_x generation of each pathway in different reaction areas in the combustion chamber was obtained. The results show that NO_x produced by pure CH₄ combustion mainly comes from three pathways： thermal NO_x， prompt NO_x and N₂O-intermediate NO_x. It is found that thermal and N₂O-intermediate NO_x emission increase with the increase of adiabatic flame temperature. With the addition of H₂ in CH₄ or CO， the total NO_x emission decreases and the rate of prompt NO_x decreases， especially in the flame brush area. In addition， NO_x emission increases with the CO mole fraction increasing in the CH₄/CO mixture.