Zhao Lifeng, Wang Defu
School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China.
School of Transportation Science and Engineering, Beihang University, Beijing 100191, China.
ACS Omega. 2020 Mar 23;5(12):6556-6565. doi: 10.1021/acsomega.9b04279. eCollection 2020 Mar 31.
Biobutanol is a promising alternative fuel for spark-ignition engines. Exhaust gas recirculation (EGR) and air dilution were evaluated on a TGDI engine fueled with butanol-gasoline (B20) in view of engine operation, efficiency, gaseous emissions, and PM emissions. For the B20 engine, EGR affected combustion more strongly than excess air dilution; the brake thermal efficiency (BTE) under excess air dilution was much higher than that with EGR. The oxygen concentration in the cylinder was also markedly reduced with EGR relative to air dilution, as the partial fresh charge was substituted with nonreactive gas. A reduced oxygen concentration contributed to differences in combustion between excess air dilution and EGR. Higher BTE was observed during combined EGR and excess air dilution operation, though it was slightly lower than that under excess air dilution alone. NO was also markedly reduced by the combination of EGR and excess air dilution, but was slightly higher than that with EGR alone. Under combined dilution conditions, the particle number (PN) emissions from the B20 engine were reduced significantly, particle sizes decreased, and the nucleate PN significantly decreased.
生物丁醇是一种很有前景的火花点火式发动机替代燃料。考虑到发动机运行、效率、气体排放和颗粒物排放，对一台使用丁醇 - 汽油（B20）的涡轮增压直喷（TGDI）发动机进行了废气再循环（EGR）和空气稀释评估。对于B20发动机，EGR对燃烧的影响比过量空气稀释更强；过量空气稀释下的制动热效率（BTE）远高于EGR时的制动热效率。与空气稀释相比，EGR还使气缸内的氧气浓度显著降低，因为部分新鲜充量被非反应性气体替代。氧气浓度降低导致了过量空气稀释和EGR之间燃烧的差异。在EGR与过量空气稀释联合运行期间观察到更高的BTE，尽管略低于仅进行过量空气稀释时的BTE。EGR与过量空气稀释相结合也显著降低了NO排放，但略高于仅使用EGR时的排放。在联合稀释条件下，B20发动机的颗粒数量（PN）排放显著降低，粒径减小，核态PN显著减少。
