The use of natural gas (NG) in dual-fuel heavy-duty engines has the potential to reduce pollutant and greenhouse gas (GHG) emissions from the transport sector when compared to the conventional diesel engines. However, NG composition and methane slip are of interest because both can adversely affect the benefits of NG as an alternative fuel, especially when considering GHG emissions. Therefore, this study experimentally investigated the effects of NG fuel properties on the performance and emissions of both conventional dual-fuel and reactivity-controlled compression ignition (RCCI) engine operations. Three different gas mixtures were selected to simulate typical NG compositions available in the world market, with methane numbers (MN) of 80.9, 87.6 and 94.1. These fuels were tested in a single-cylinder compression ignition engine operating at 0.6, 1.2 and 1.8 MPa net indicated mean effective pressure (IMEP). A high-pressure common rail system allowed for the use of various diesel injection strategies while a variable valve actuation system enabled the effective compression ratio to be adjusted via late intake valve closing (LIVC). The RCCI combustion was found to be more sensitive to changes in MN than the conventional NG-diesel dual-fuel operation. The gas mixture with the lowest MN reduced both total unburned hydrocarbons emissions and methane slip at the expense of higher nitrogen oxides (NOx) emissions. The effects of MN on the net indicated efficiency were more significant at 0.6 MPa IMEP, yielding differences of up to 4.9% between the RCCI operations with the lowest and highest MN fuels. Overall, this work revealed that the combination of the RCCI combustion and LIVC can achieve up to 80% lower methane slip and NOx emissions and relatively higher net indicated efficiency than the conventional dual-fuel regime, independent of the NG composition.

与传统柴油发动机相比，在双燃料重型发动机中使用天然气（NG）具有减少交通运输部门污染物和温室气体（GHG）排放的潜力。但是，NG组成和甲烷泄漏很重要，因为它们都会对NG作为替代燃料的益处产生不利影响，尤其是在考虑温室气体排放时。因此，本研究通过实验研究了天然气燃料特性对常规双燃料和反应控制的压缩点火（RCCI）发动机性能和排放的影响。选择了三种不同的气体混合物来模拟世界市场上可用的典型天然气成分，甲烷数（MN）为80.9、87.6和94.1。这些燃料是在单缸压缩点火发动机中以0.6、1进行测试的。净重2和1.8 MPa表示平均有效压力（IMEP）。高压共轨系统允许使用各种柴油喷射策略，而可变气门致动系统则可以通过延迟进气门关闭（LIVC）来调节有效压缩比。发现RCCI燃烧比常规的NG柴油双燃料操作对MN的变化更敏感。MN最低的混合气体减少了总的未燃烧碳氢化合物排放量和甲烷泄漏量，但以较高的氮氧化物（NOx）排放量为代价。在0.6 MPa IMEP下，MN对净指示效率的影响更为显着，使用最低和最高MN燃料的RCCI操作之间的差异高达4.9％。总体，