甲烷掺氢自点火非平衡态热力学损分析

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 CH₄/H₂ 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 CH₄/H₂ 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, H₂ addition shows little effect on the total exergy destruction, but effectively extends the low exergy destruction zone of CH₄ combustion. The time histories of exergy destruction at different temperatures and varied H₂ additions are compared; the rates of production (ROP) of HO₂ and OH 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 H₂ addition on exergy destruction of CH₄ combustion. Furthermore, the discrepancy in exergy destruction between CH₄ 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 H₂ addition on exergy destruction during CH₄ combustion at molecular reaction level, and is expected to provide theoretical guidance for further reducing exergy destruction of hydrogen-natural gas engine combustion.