基于仿真的不同添加成分对HCCI天然气发动机性能影响

Effect of different additives on performance of natural gas HCCI engine based on simulation

该文针对天然气混合均质压燃(HCCI)发动机存在的低负荷易失火问题,基于一台改装的单缸机搭建了相应的三维模型,从缸内燃烧特性和助燃机理两方面对比分析了氢气(H_(2))、臭氧(O_(3))和二甲醚(DME)3种气态添加成分对天然气HCCI发动机性能的影响。结果表明,3种添加成分均能改变天然气空气混合气的自燃燃烧特性,增强着火能力,提前燃烧相位,均可实现天然气HCCI向低负荷范围扩展;自由基OH是强化天然气HCCI燃烧的重要组分,H_(2)和O_(3)的助燃机理在于增加自由基OH浓度,加快甲烷消耗反应速率,DME的助燃机理在于引燃天然气;H_(2)是一种扩展天然气HCCI发动机低负荷运行边界的优良添加成分。

Aiming at the misfire problem of natural gas mixed homogeneous compression ignition(HCCI)engine at low load,a three-dimensional model of the modified single cylinder engine was built to study the effect of hydrogen(H_(2)),ozone(O_(3))and dimethyl ether(DME)as the additives on combustion characteristics and combustion-supporting mechanism.The results show that the three additive components can change the autoignition characteristics of natural gas-air mixture,enhance the ignition ability,and advance the combustion phase,all of which can realize the expansion of natural gas HCCI to the low load range.Radical OH is an important component to enhance the combustion of natural gas HCCI.The combustion-supporting mechanism of H_(2) and O_(3) is to increase the concentration of free-radical OH and accelerate the reaction rate of methane consumption,while combustion-supporting mechanism of DME is to ignite natural gas.H_(2) is an excellent additive to extend the low load operation boundary of natural gas HCCI engine.