机内净化降低船用二冲程柴油机NOx排放仿真

摘要

针对一台满足Tier Ⅱ排放标准的船用二冲程柴油机,建立GT-Power一维仿真模型,研究了废气再循环(EGR)、米勒循环、进气加湿(HAM)以及优化喷油正时等手段对NOx排放和燃油消耗率的影响,并探讨了通过多种措施耦合来实现Tier Ⅲ排放标准的技术路线.结果表明:单独采用米勒循环或进气加湿难以达到Tier Ⅲ排放标准;通过结合米勒循环和进气加湿,可以将NOx排放降低至Tier Ⅲ标准,但会导致燃油消耗率大幅增加;废气再循环是降低NOx排放的最有效措施,通过将其与米勒循环和进气加湿相结合,可有效减小EGR使用率,并适度改善燃油经济性的恶化程度.%One-dimensional simulation was employed to evaluate the potential in-cylinder NOx control approaches on a low-speed 2-stroke marine diesel engine in order to meet the international maritime organization (IMO) Tier Ⅲ NOx emission standard.Based on the established GT-Power model,the influence of exhaust gas recirculation (EGR),Miller-cycle,humid air motor (HAM) and injection timing on both NOx emissions and brake specific fuel consumption (BSFC)were studied.Results show that only using Miller-cycle or HAM is not capable of meeting IMO Tier Ⅲ emission standard.When combining Miller-cycle with HAM,NOx emissions are dramatically decreased to Tier Ⅲ requirement but the BSFC also increases significantly.Among the three NOx control approaches,EGR is found to be the most effective approach to reduce NOx emissions.By further combining EGR with Miller-cycle and HAM,the fuel economy can be improved at a reduced EGR rate requirement.