甲烷掺氢自点火非平衡态热力学[火用]损分析  

Non-Equilibrium Thermodynamic Analysis on Exergy Destruction During Auto-Ignition of Methane-Hydrogen Blends

作　　者：伍宏环 洪聪结 曹军[1] 黄佐华[1] 张英佳[1] WU Honghuan;HONG Congjie;CAO Jun;HUANG Zuohua;ZHANG Yingjia(State Key Laboratory of Multiphase Flows in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,西安710049

出　　处：《西安交通大学学报》2022年第11期138-147,共10页Journal of Xi'an Jiaotong University

基　　金：国家自然科学基金资助项目(51888103)。

摘　　要：为明晰天然气掺氢发动机非平衡燃烧过程主要[火用]损源,本文利用自点火压力时程对文献中5个代表性CH_(4)/H_(2)燃烧动力学模型性能进行再评估,基于非平衡态热力学理论初步建立了基元反应[火用]损评估方法,结合详细动力学模型分析了不同约束条件下(温度、当量比、掺氢比)CH_(4)/H_(2)混合气自点火过程中基元反应[火用]损贡献及其变化规律。结果表明,反应初始温度升高,化学反应[火用]损减少,不完全燃烧损失增加。H_(2)掺混虽未显著降低CH_(4)燃烧最低[火用]损值,但有效扩展了CH_(4)低[火用]损燃烧区。对比了不同温度、不同掺氢比下[火用]损速率和总[火用]损的时程演化,分析了H_(2)和H自由基产率及其主导基元反应[火用]损贡献,揭示了初始温度和掺氢对燃烧[火用]损影响的动力学机制。进一步对比不同反应路径关键物种吉布斯自由能,从热力学角度解释了CH_(4)高/低温氧化路径[火用]损差异。研究结果在基元反应水平上揭示了H_(2)介入对CH_(4)燃烧[火用]损的影响机制,可为探索减少天然气掺氢发动机[火用]损的控制方法提供理论依据。This paper analyzes the main sources of exergy destruction during the non-equilibrium combustion of the hydrogen-natural gas engine.The performance of five representative CH_(4)/H_(2) kinetic models in the literature is re-evaluated and a method for calculating exergy destruction of elementary reactions is preliminarily established based on non-equilibrium thermodynamics.Combined with the selected kinetic model,the exergy destruction behaviors during the auto-ignition of CH_(4)/H_(2) mixtures under different initial conditions(temperatures,equivalence ratios,hydrogen ratios)are numerically analyzed.According to the results,with the initial temperature increases,exergy destruction caused by chemical reaction decreases,while exergy destruction from incomplete combustion increases.Moreover,H_(2) addition shows little effect on the total exergy destruction,but effectively extends the low exergy destruction zone of CH_(4) combustion.The time histories of exergy destruction at different temperatures and varied H_(2) additions are compared;the rates of production(ROP)of H_(2) and H radicals,as well as the contribution of the elementary reactions that dominate their generation and consumption to the exergy destruction,are analyzed,to reveal the effects of initial temperature and H_(2) addition on exergy destruction of CH_(4) combustion.Furthermore,the discrepancy in exergy destruction between CH_(4) high-/low-temperature oxidation pathways is thermodynamically clarified by comparing the Gibbs free energy of key species during fuel oxidation.The research results reveal the effects of H_(2) addition on exergy destruction during CH_(4) combustion at molecular reaction level,and is expected to provide theoretical guidance for further reducing exergy destruction of hydrogen-natural gas engine combustion.

关 键 词：自点火 掺氢 非平衡态热力学 反应[火用]损 基元反应 

分 类 号：TK431[动力工程及工程热物理—动力机械及工程]