甲醇-正庚烷混合燃料两阶段着火的动力学特性

蒲一帆，庄远^*

合肥工业大学汽车与交通工程学院，安徽 合肥  230009

摘要：基于CHEMKIN软件，分析添加甲醇对正庚烷在高、低温条件下两阶段着火的影响，对甲醇与正庚烷在着火过程中的相互作用机理开展动力学研究。结果表明：在初始低温下，甲醇与正庚烷对OH自由基的竞争抑制了正庚烷的低温链支化反应，延长了燃料第一阶段的着火时间；随着甲醇掺混比例的增加，低温反应强度进一步受到抑制，无法检测到明显的低温着火现象；添加甲醇后，HO₂自由基的浓度增加，有利于H₂O₂的生成，高温下H₂O₂通过分解反应产生大量的OH自由基，加速了第二阶段着火；在初始高温下掺入少量甲醇，着火时刻明显提前，但是掺混的甲醇过多，着火时刻逐渐推迟。

关键词：甲醇；正庚烷；着火延时；化学反应动力学

Kinetic characteristics on two-stage ignition of fuel combined with methanol and n-heptane

PU Yifan，ZHUANG Yuan*

School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei 230009, China

Abstract：Based on the CHEMKIN software, the effect of methanol addition on the two-stage ignition of n-heptane at high and low temperatures is investigated to reveal the interaction mechanism between methanol and n-heptane in the ignition process, and the corresponding kinetic study is carried out. The results show that at the initial low temperature, the competition of methanol for OH radicals inhibits the low-temperature chain branching reaction of n-heptane, which prolongs the first-stage ignition of the fuel. With the increase of methanol substitution percent，the intensity of the low-temperature reaction is further inhibited and no obvious low-temperature ignition phenomenon could be detected. However, the increase in the concentration of HO2 radicals after methanol addition promotes H₂O₂production. HH₂O₂generates a large amount of OH radicals through decomposition reaction at high temperature, which promotes the second-stage ignition. In contrast to the inhibitory effect of methanol at low initial temperatures, the ignition time at high initial temperatures is significantly advanced by blending a few amounts of methanol, but the ignition time is gradually delayed again by blending an excessive amount of methanol.

Keywords:methanol; n-heptane; ignition delay; chemical reaction kinetics