Numerical study on auto-ignition characteristics of hydrogen-enriched methane under engine-relevant conditions
Numerical study on auto-ignition characteristics of hydrogen-enriched methane under engine-relevant conditions
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发动机相关条件下富氢甲烷自燃特性的数值研究
DOI：
10.1016/j.enconman.2019.112092
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发表时间：
2019-11
影响因子：
10.4
通讯作者：
Banglin Deng
中科院分区：
文献类型：
--
作者：
Yongxiang Zhang;Jianqin Fu;Jun Shu;Mingke Xie;Jingping Liu;Tao Jiang;Zhuoyin Peng;Banglin Deng
摘要火花点火发动机的爆震燃烧是指一部分未燃烧的燃料-空气混合气的自燃。本文对富氢甲烷在发动机相关条件下的自燃特性进行了详细的化学动力学机理的数值研究。与实验数据比较，USC Mech 2.0机制最符合，并将其用于灵敏度分析、产率（ROP）分析和反应途径分析。结果表明：在高温高压下，随着氢分数的增加，CH4/H2燃料混合物的点火延迟时间（IDs）显著降低（最多降低2个数量级），但在低温下下降幅度不明显（在37.3%以内）；灵敏度分析表明，在高温下反应（R1）与反应（R2、R3）相互促进，而在低温下只有反应（R3）单方面促进反应（R12）。ROP分析表明，加氢对甲烷IDs的降低是通过增加H、O和OH自由基的生成来实现的。有趣的是，CH4/H2燃料混合物的IDs在不同温度下呈现出不同的变化趋势，随着当量比的增加，低温时最大降低47.5%，高温时最大增加132.7%。灵敏度分析表明，CH4/H2燃料混合物的着火动力学主要取决于低温CH4浓度而不是高温氧浓度。本研究不仅补充了CH4/H2燃料混合物在高压下燃烧的基础研究，而且揭示了加氢和当量比对CH4/H2燃料混合物在高压下IDs的影响机理。更重要的是，它可能为火花点火（SI）发动机的爆震燃烧控制提供基础性的见解。
Abstract Knocking combustion for spark-ignition engine is related to auto-ignition of a portion of the unburned fuel-air mixture. In this investigation, the detailed chemical kinetic mechanism was engaged to numerically study the auto-ignition characteristics of hydrogen-enriched methane under engine-relevant conditions. Compared with the experimental data, the USC Mech 2.0 mechanism obtained the closest agreement, and it was adopted in the sensitivity analysis, the rate of production (ROP) analysis and the reaction pathway analysis. Results showed that at high temperature and high pressure, the ignition delay times (IDs) of CH4/H2 fuel blends reduce significantly (by two orders of magnitude at most) with rising hydrogen fraction, but the decline rate is not so obvious (within 37.3%) at low temperature. The sensitivity analysis indicated that at high temperature the reaction (R1) and reactions (R2, R3) promote each other while at low temperature only the reaction (R3) unilaterally facilitates the reaction (R12). The ROP analysis implied that the decrease of IDs of methane by hydrogen addition is realized through increasing the H, O, and OH radical production. Interestingly, the IDs for CH4/H2 fuel blends show different trends at different temperature, which decrease (by 47.5% at most) at low temperature but increase (by 132.7% at most) at high temperature as the equivalence ratio rises. The sensitivity analysis showed that the ignition kinetics for CH4/H2 fuel blends more depend on the CH4 concentration at low temperature but oxygen concentration at high temperature. This investigation not only supplements the fundamental combustion studies of CH4/H2 fuel blends in elevated pressures, but also reveals the influence mechanism of hydrogen addition and equivalence ratio on the IDs of CH4/H2 fuel blends at high pressure. More importantly, it may offer fundamental insights for the control of knocking combustion of spark-ignition (SI) engine.
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