基于EGR技术的船用低速二冲程柴油机增压系统匹配研究

Research on Turbocharging Systems Matching with Marine Low-Speed Two-Stroke Diesel Engines Using EGR

针对采用EGR技术的船用低速二冲程柴油机在满足IMO排放法规时增压系统须兼顾多模式、宽流量范围运行的问题,基于某型低速二冲程柴油机在GT-Power软件中搭建整机及EGR系统仿真模型并校核。在此基础上研究涡轮增压器匹配、进排气旁通、废气旁通(EGB)等措施对该型柴油机TierⅢ和TierⅡ模式时性能的影响并得出系统匹配策略。研究结果表明:TierⅢ模式时,减小涡轮等效流通面积可有效恢复增压压力,但导致运行点接近压气机喘振线;引入进排气旁通则可有效解决喘振问题。TierⅡ模式时,采用EGR和EGB措施均可有效解决因涡轮等效面积减小带来的增压压力过高问题,但其中EGR方案NO_x排放较低,燃油消耗率偏高,而EGB方案燃油消耗率较低,NO_x排放偏高;综合应用EGR和EGB,即高负荷采用EGR,中低负荷采用EGB的匹配方案,可达到整机NO_x排放满足TierⅡ法规要求且燃油消耗率最低的设计目标。

To meet with IMO emissions regulations, the matching of turbocharging systems with marine low-speed two-stroke diesel engines using exhaust gas recirculation （EGR） technology should take the is- sues of multi-mode, wide flow range operation into consideration. An engine simulation model with the EGR system was established and calibrated with GT-Power software based on a type of low-speed two stroke diesel engine. Effects of the turbocharger matching, intake and exhaust bypass, exhaust gas bypass on the engine performance under Tier III and Tier II restrictions were analyzed and the turboeharger matching strategies were obtained. Results show that in the Tier m mode, reducing turbine equivalent ar- ea can effectively restore the boost pressure, however the operating points are close to the compressor sur- ging line; the introduction of intake and exhaust bypass can effectively solve the surging problem. In the Tier ]I mode, the EGR and EGB schemes can effectively solve the high charging pressure caused by the decreased turbine equivalent area. The comparison results show that NOx emissions are low and BSFC is high in the EGR scheme; BSFC is low and the NOx emissions are high in the EGB scheme. To achieve the optimized fuel economy under the Tier II NOx restrictions, the EGR and EGB strategy should he ap- plied comprehensively, which means the EGR strategy should be adopted at high loads and the EGB strat- egy applied at medium to low loads.