牛培铮,吴朝晖,董晶瑾,李敬瑞,刘海峰,尧命发.米勒循环协同废气再循环对高压直喷天然气船机的影响研究[J].内燃机工程,2019,40(6):64-70.
米勒循环协同废气再循环对高压直喷天然气船机的影响研究
Numerical Investigation of Effect of Miller Cycle and Exhaust Gas Recirculation on High-Pressure Direct-Injection Natural Gas Marine Engines
DOI：10.13949/j.cnki.nrjgc.2019.06.010
关键词:天然气  米勒循环  废气再循环  微引燃  低速船机  计算流体动力学
Key Words:natural gas  Miller cycle  exhaust gas recirculation(EGR)  pilot ignition  low-speed marine engine  computational fluid dynamics(CFD)
基金项目:船用低速机工程（一期）研制项目（CDG01-KT0308）
作者单位
牛培铮,吴朝晖,董晶瑾,李敬瑞,刘海峰,尧命发 1.天津大学 内燃机燃烧学国家重点实验室,天津 300072； 2.中船动力研究院有限公司,上海 200120 
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摘要:基于CONVERGE建立了高压直喷（high pressure direct injection, HPDI）天然气低速船机三维仿真模型,并基于该模型研究了米勒循环和废气再循环（exhaust gas recirculation, EGR）对发动机燃烧特性及污染物排放的影响规律,探究了米勒循环耦合EGR路线满足Tier Ⅲ排放法规的可行性。研究结果表明,单独使用30%EGR率可满足Tier Ⅲ排放标准,但指示油耗和碳烟排放增加显著；应用米勒循环降低NOx 排放的潜力低于EGR；过大的排气门晚关角度会增大压气机工作负荷,且降低等量NOx 排放情况下油耗牺牲较大；采用25%EGR率耦合小程度米勒循环（排气门关闭时刻推迟5°曲轴转角）并适当提前天然气喷射正时（提前2°曲轴转角）,可在指示油耗仅增加158%的前提下降低77%的NOx 排放,是满足Tier Ⅲ排放法规可行的技术路线。
Abstract:Based on a three-dimensional simulation model established using CONVERGE, the effects of exhaust gas recirculation and the Miller cycle on the combustion characteristics and emissions were studied to explore the feasibility of the Miller cycle coupled with EGR to meet Tier Ⅲ emission regulations for low-speed high-pressure direct injection natural gas marine engines. The results show that using 30% of EGR rate alone can meet Tier Ⅲ emission standards, but with a significant increase in the indicated fuel consumption and soot emissions; the Miller cycle is not as effective as EGR in the potential to reduce NOx emissions; excessive exhaust valve closing delay will cause increase in compressor workload, and lead to a considerable increase in fuel consumption when the same amount of NOx emissions is reduced. Coupling mild Miller cycle(delaying exhaust valve closing by 5° in crank angle) with 25% of EGR rate and the proper natural gas injection timing(advancing 2° in crank angle) can reduce NOx emissions by 77% with only a slight increase in the fuel consumption by 1.58%, which is a feasible way to meet Tier Ⅲ emission regulations.
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