压缩比对直喷天然气发动机燃烧与排放特性的影响  

Effect of Compression Ratio on Combustion and Emission Characteristics of a Direct-Injection Natural Gas Engine

作　　者：郑建军[1] 王金华[1] 王彬[1] 黄佐华[1] 宁德忠[1] 张英佳[1] 

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,陕西西安710049

出　　处：《内燃机学报》2010年第1期20-25,共6页Transactions of Csice

基　　金：国家自然科学基金重点项目(50636040);国家重大基础研究计划项目(2007CB210006)

摘　　要：在缸内直喷火花点火天然气发动机上开展了压缩比为8、10、12和14的燃烧和排放特性研究。研究结果表明,压缩比对发动机性能、燃烧和排放有较大影响。压缩比增加,发动机充量系数增加,燃烧速率加快,热效率提高。缸内最高燃烧压力、最高燃气平均温度和最大压力升高率等燃烧参数随压缩比的增加而增加;HC和CO排放随压缩比的增加而降低,NOx随压缩比的增加而增加。压缩比过高会导致HC排放的增加,当压缩比大于12时,发动机在中高负荷出现轻微爆燃现象,NOx排放明显增加。综合考虑直喷式天然气发动机的动力性、经济性和排放性能,认为发动机的最佳压缩比设置在12比较合理。An experimental study on combustion and emission characteristics of a direct-injection sparkignition engine fueled with natural gas under various compression ratios was investigated. The results show that the compression ratio has a significant influence on the engine performance, combustion and emissions. When compression ratio is increased, the volumetric efficiency is increased, giving a fast burning rate and thus high thermal efficiency and power output. The maximum rate of heat release increases with the increase of compression ratio while the flame development duration decreases with the increase of compression ratio, and these behavior become more obviously with the increase of compression ratio at the small load or lean mixture combustion. This indicates that compression ratio has a significant influence on combustion duration for lean mixture combustion. Exhaust HC and CO emissions decrease with the increase of compression ratio, while exhaust NOx increases with the increase of compression ratio. However, the exhaust HC emission tends to increase at higher compression ratio. Light knock is observed at high load at compression of 14, leading to the increase of NOx. Compression ratio of 12 is a reasonable value for the compressed natural gas direct-injection engine based on the experimental study.

关 键 词：天然气 压缩比 缸内直喷 发动机 燃烧 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]