改变压缩比对正庚烷HCCI发动机燃烧及排放特性影响的模拟研究  

Simulation Study on Combustion and Emission Characteristics of N-heptane HCCI Engine with Varying Compression Ratio

作　　者：李延吉[1] 宋瑞雯 马婕 董春良 LI Yanji;SONG Ruiwen;MA Jie;DONG Chunliang(Clean Energy Key Laboratory of Liaoning,Shenyang Aerospace University,Shenyang 110136,China)

机构地区：[1]沈阳航空航天大学清洁能源利用辽宁省重点实验室,辽宁沈阳110136

出　　处：《内燃机》2023年第3期1-11,共11页Internal Combustion Engines

基　　金：辽宁省自然科学基金项目(20180550324);辽宁省教育厅项目(L201707)。

摘　　要：为研究压缩比的改变对正庚烷均质充量压燃(HCCI)发动机的燃烧特性及排放的影响,本研究基于CHEMKIN中的ICE模型,模拟了正庚烷HCCI发动机在压缩比为11~15时的燃烧及排放特性,研究结果揭示了压缩比的改变对正庚烷HCCI燃烧及排放的主要基元反应及化学动力学的影响方式。研究结果显示,压缩比增大使低温燃烧阶段的着火时刻稍有提前,负温度系数(NTC)区持续时间缩短,高温燃烧阶段的着火时刻提前明显,缸内温度压力峰值随之变大,放热率增势减缓,整体燃烧放热持续期缩短,着火时刻不断提前,正庚烷分解速率加快。OH自由基的总反应速率加快,增大压缩比对高温蓝焰反应速率影响较大使得OH自由基到达峰值浓度时刻提前,着火延迟期缩短。此外,压缩比的变化对CO和CO_(2)的生成量影响较小,但加快了CO转化为CO_(2)的反应速率,NO的浓度显著上升,压缩比增大主要增加了热力型NO的形成。In order to investigate the effects of compression ratio changes on the combustion characteristics and emissions of a stoichiometric homogeneous charge compression ignition(HCCI)engine fueled with n-heptane,this study employed the ICE model based on CHEMKIN to simulate the combustion and emission characteristics of the n-heptane HCCI engine at compression ratios ranging from 11 to 15.The research aimed to reveal the primary elementary reactions and chemical kinetics influenced by the variation in compression ratio on the combustion and emissions of n-heptane in HCCI engines.The results demonstrated that with an increase in compression ratio,the ignition timing of the low-temperature combustion stage slightly advanced,the duration of the NTC(negative temperature coefficient)region was reduced,and the ignition timing of the high-temperature combustion stage significantly advanced.Moreover,the peak temperatures and pressures inside the cylinder increased with the rising compression ratio.The rate of heat release showed a decreasing growth trend,resulting in a shorter overall duration of combustion heat release.The ignition timing continuously advanced,and the decomposition rate of n-heptane accelerated.The total reaction rate of OH radicals increased,and the influence of compression ratio on the reaction rate of high-temperature blue flame was significant.Consequently,the timing of peak OH radical concentration was brought forward,and the ignition delay period was shortened.Additionally,the change in compression ratio had a minor effect on the production of CO and CO_(2).However,it accelerated the reaction rate of CO conversion to CO_(2).The concentration of NO increased significantly,and the increase in compression ratio primarily contributed to the formation of thermal NO.

关 键 词：正庚烷 均质充量压燃 压缩比 化学反应动力学 

分 类 号：TK432[动力工程及工程热物理—动力机械及工程]