摘要
为了完整表达双燃料发动机湍流燃烧过程中湍流流动和化学反应的共同影响,在燃烧过程数值计算中将湍流和化学反应机理模型耦合,考虑两者的相互作用,成为可行的办法。在开展不同LNG替代率下双燃料发动机缸内工作过程数值模拟时,将构建的柴油引燃天然气化学反应机理模型耦合到CFD软件中计算,并考虑湍流和化学反应的相互作用。湍流流动采用RNG k-ε模型,化学反应机理模型由简化而来的正庚烷机理(162组分和692步基元反应)、甲烷机理(26组分和122步基元反应)以及扩展的NO热力学机理(3步反应)组成,湍流和化学反应之间的相互作用通过Kong模型建立。结果表明,双燃料工况下发动机的缸内压力要低于纯柴油工况,但氮氧化物的生成也要小于纯柴油工况,且随着LNG替代率的增加,天然气燃烧始点也逐渐延长,缸内压力以及缸内温度峰值也随之下降,氮氧化物的生成也会下降。
In order to fully express the common influence of turbulent flow and chemical reaction in the turbulent combustion process of dual fuel engine,it is feasible to couple the turbulent flow and chemical reaction mechanism model in the numerical calculation of combustion process,and consider the interaction between them.During the numerical simulation of the in-cylinder working process of a dual-fuel engine with different LNG substitution rates,the established chemical reaction mechanism model of diesel-ignited natural gas was coupled to CFD software for calculation,and the interaction of turbulence and chemical reaction was considered.RNG k-εmodel was used for turbulent flow.The chemical reaction mechanism model was composed of reduced n-heptane mechanism(162 component and 692 step elementary reaction),reduced methane mechanism(26 component and 122 step elementary reaction)and extended NO thermodynamic mechanism(3-step reaction).The interaction between turbulence and chemical reaction was established by Kong model.The results show that the in-cylinder pressure of the engine under dual-fuel condition is lower than that under pure diesel condition,but the generation of nitrogen oxides is also lower than that under pure diesel condition.Moreover,with the increase of the replacement rate of LNG,the starting point of natural gas combustion is gradually prolonged,the in-cylinder pressure and in-cylinder temperature peak also decrease,and the generation of nitrogen oxides also decreases.
作者
刘玉坪
肖民
黄志伟
刘松岭
LIU Yu-ping;XIAO Min;HUANG Zhi-wei;LIU Song-ling(College of Energy and Power Engineering,Jiangsu University of Science and Technology,Zhenjiang 212000,China)
出处
《舰船科学技术》
北大核心
2021年第6期122-129,共8页
Ship Science and Technology
关键词
化学反应
燃烧模型
LNG缸内液喷
替代率
chemical reaction
combustion model
LNG direct injection
substitution rate
