A Numerical Study of the Effects of Using Reformer Gas on Ignition Characteristics under Dual-Fuel Engine-Relevant Conditions

Abstract

Natural gas/diesel dual-fuel engine has become an urgent need to alleviate the energy crisis and reduce emissions. As an additive, reforming gas can improve the combustion process of dual-fuel engines because it improves the combustion rate and compensates for the low reactivity of natural gas. Therefore, it is of great significance to study the ignition characteristics of natural gas diesel blends by adding H2 and syngas. Based on ANSYS Chemkin 17.0 software, the ignition delay time was solved by a closed uniform model. The effects of H2 and syngas on the ignition performance of a natural gas/diesel engine were studied. The results showed that the ignition delay time of the methane/n-heptane mixture was prolonged after adding H2 in the range of medium and low temperatures. This was due to the fact that reaction R3 (OH + H2 = H + H2O) was an endothermic reaction, which consumed OH radicals and inhibited the ignition process. In the high-temperature range, adding H2 reduced the ignition delay time of the mixture system, which was because of the significant increase in the sensitivity coefficients of R1(H + O2 = O + OH) and R3 and the generation of OH radicals. Therefore, the reduction in ignition delay caused by H2 addition in the high-temperature regions was mainly attributed to R3 and R1. In syngas, CO reduced the ignition delay time of methane/syngas/n-heptane. However, the addition of CO could reduce the importance of R3 in the reaction process—resulting in the weakening of the influence of H2 on ignition delay. This study can expand the theoretical basis of ignition characteristics of methane/n-heptane mixture with H2 and syngas under dual-fuel engine-relevant conditions.

Maximum reduction in greenhouse gas emissions by complete replacement of natural gas with pure hydrogen as a sole low reactive fuel in a RCCI engine

“…the mixture of hydrogen and CO) as an additive to gaseous hydrocarbon fuels such as natural gas, CNG, biogas, and landfill gas has been followed up in heavy-duty diesel engines under RCCI combustion. [37][38][39][40][41][42][43][44][45] However, due to global warming concern, the maximum reduction in hydrocarbon fuels consumption as the largest source of greenhouse gas emissions has also been followed up by researchers. Hence, some limited studies related to the use of pure hydrogen as a sole low reactive fuel in diesel engines under dual-fuel mode of combustion and more recently under RCCI combustion has been conducted.…”