缸内液喷LNG/柴油双燃料发动机燃烧特性

以L 21/31船用中速柴油机为原型,在不改变燃烧室结构的基础上将其改装成缸内液喷LNG/柴油双燃料发动机,利用AVL_FIRE软件展开三维数值模拟,研究此双燃料发动机的LNG替代率极限以及高替代率时的缸内燃烧及排放性能。研究结果表明：改装后双燃料发动机的LNG替代率极限为99.5%,当替代率大于99.5%时,LNG无法被引燃；在可以正常燃烧条件下,保持引燃柴油及液化天然气喷射正时和喷射时间间隔不变,随着液化天然气替代率的增加,液化天然气燃烧始点基本不变,缸内最大爆发压力和最高燃烧温度降低,NO、CO生成量和排放量降低。

Research on Combustion Characteristics of In-cylinder Liquid Injection LNG/Diesel Dual Fuel Engine

Based on the L21/31 marine medium-speed diesel engine, it was converted into a diesel/LNG in-cylinder liquid injection dual-fuel engine without changing the structure. Using AVL_FIRE, the three-dimensional numerical research was carried out on the limit of LNG replacement rate for the dual-fuel engine and the combustion characteristics of in-cylinder liquid injection in high replacement rates. The results show that, in this paper, the limit of the LNG replacement rate is 99.5%, and if the rate is more than 99.5%, the LNG cannot be ignited; For the normal combustion conditions, keep pilot diesel and LNG injection time intervals and injection timing constant, with the increase of LNG replacement rate, the combustion timing of LNG is basically unchanged, the maximum burst pressure and the maximum combustion temperature are gradually reduced, the NO and CO emissions are also reduced.