Development of a Skeletal Mechanism with NOx Chemistry for CH4/H2 Combustion over a Wide Range of Hydrogen-Blending Ratios

An accurate and efficient skeletal mechanism is critical to describe the combustion chemistry of CH4/H2 with nitrogen oxides (NOx) through computational fluid dynamics (CFD) simulations. In this paper, the performance of the 11 classical/state-of-the-art detailed C/H/O/N mechanisms (1995–2020) for predicting combustion of CH4, H2, and their mixtures is comprehensively and quantitatively evaluated. Based on the best-performing one Glarborg2018, a 60-species and 566-reaction skeletal C1–2/H/O/N mechanism with NOx chemistry for CH4/H2 combustion over a wide range of hydrogen-blending ratios from 0 to 100% is developed using the directed relation graph with error propagation (DRGEP), sensitivity analysis (SA), and quasi-steady-state-approximation (QSSA) methods. Also, the present newly developed skeletal mechanism is comprehensively evaluated against large numbers of available experimental data (∼3500 data points) for combustion of CH4, H2, and their mixtures, in terms of ignition delay times, laminar burning velocities, flame structures (i.e., temperature and species (reactants, intermediates, and final products, including CH4, H2, O2, CO, CO2, CH2O, C2H4, C2H6, N2, and H2O) concentrations), NOx emissions, as well as NO formation and reduction via different submechanisms. Results show that Glarborg2018 performs best in predicting NO from combustion of CH4, H2, and their mixtures, especially at high temperatures. The present newly developed skeletal mechanism can reasonably well predict NOx emissions in CH4/H2 combustion over a wide range of hydrogen-blending ratios from 0 to 100% at low-/intermediate-/high-temperature levels (e.g., 650–2200 K), which is superior to the existing skeletal ones; in particular, thermal NO, prompt NO, NO formed via NNH and N2O-intermediate, as well as NO reduced by HCCO/CHi=0–3 and H can be separately reproduced. In conclusion, the present newly developed skeletal C1–2/H/O/N mechanism preserves comparable prediction accuracy compared to its parent Glarborg2018 and is applicable to model combustion of CH4, H2, and their mixtures with NOx chemistry over a wide range of low, intermediate, and high temperatures.

精准高效的骨架机理对于通过计算流体动力学（CFD）模拟描述含氮氧化物（NOx）的CH₄/H₂燃烧化学过程至关重要。本文针对11套经典/当前领先的C/H/O/N类详细机理（1995–2020年）在预测CH₄、H₂及其混合燃料燃烧行为的表现，开展了全面且定量的评估。基于表现最优的Glarborg2018机理，本文采用误差传播定向关系图（DRGEP）、敏感性分析（SA）与准稳态近似（QSSA）方法，开发了一套包含NOx化学过程的60组分、566反应的C₁–₂/H/O/N骨架机理，可适用于氢掺混比覆盖0至100%宽范围的CH₄/H₂燃烧场景。此外，本文针对CH₄、H₂及其混合燃料的大量公开实验数据（约3500组数据点），从点火延迟时间、层流燃烧速度、火焰结构（即温度与组分浓度，涵盖反应物、中间产物与最终产物，包括CH₄、H₂、O₂、CO、CO₂、CH₂O、C₂H₄、C₂H₆、N₂及H₂O）、NOx排放，以及通过不同子机理实现的NO生成与还原路径等维度，对新开发的骨架机理进行了全面评估。研究结果表明，Glarborg2018机理在预测CH₄、H₂及其混合燃料燃烧生成的NO方面表现最优，尤其在高温工况下。本文新开发的骨架机理可在650–2200 K等低、中、高温区间内，针对氢掺混比覆盖0至100%的CH₄/H₂燃烧场景，准确预测其NOx排放表现，性能优于现有同类骨架机理；尤其可分别复现热NO、快速NO（prompt NO）、通过NNH与N₂O中间路径生成的NO，以及被HCCO/CHᵢ=0–3与H还原的NO。综上，本新开发的C₁–₂/H/O/N骨架机理与母机理Glarborg2018的预测精度相当，可适用于宽温度区间（低、中、高温）内CH₄、H₂及其混合燃料耦合NOx化学过程的燃烧模拟。