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本文基于一台四缸点燃式涡轮增压天然气发动机,在第四缸进行加浓燃烧并将其排气(重整气)直接引入进气总管,以实现缸内热化学燃料改质.在此基础上开展了11和13压缩比下的缸内热化学燃料改质过程和整机燃烧与排放特性的研究.研究发现,压缩比增加,第四缸循环变动降低,重整气中CH4含量减少而H2和CO含量增加,缸内热化学燃料改质过程得到优化.同时,提高压缩比会使有效燃气消耗率降低,缸内最高燃烧压力增加,滞燃期和燃烧持续期缩短,整机稳定性增强.然而压缩比的增加引起THC排放增加.高压缩比下CO排放在小负荷时较低,在大负荷时较高.而NOx排放在第四缸当量比较低时随压缩比增加而增加,但在第四缸当量比较高时随压缩比增加而降低.“,”Based on a turbo-charged four-cylinder SI natural gas engine,the concept of in-cylinder thermochemical fuel reforming (TFR) was realized by running the fourth cylinder rich and routing the entire exhaust of this cylinder into the intake manifold.With this basis,the TFR process and the characteristics of engine combustion and emissions under engine compression ratio (CR) 11 and 13 were investigated.Results proved better in-cylinder TFR process for higher CR,which was signified by lower cyclic variation in the fourth cylinder,higher H2 and CO as well as lower CH4 fraction in the reformed gas.Higher CR also resulted in lower brake specific fuel consumption,higher peak cylinder pressure,lower ignition delay and combustion duration and enhanced global engine stability.Results also signified that increased CR bettered CO emission under low engine load while worsened it under high engine load.Nevertheless,engine THC emission was worsened with the increased CR.As for NOx emission,increased CR helped to lower it under lower equivalence ratio in the fourth cylinder while to increase it under higher equivalence ratio in the fourth cylinder.