Contribution to the characterization and improvement of dual-fuel engines

Abstract

Today's world depends on petroleum-based fuels, primarily gasoline and diesel, especially in the transportation sector. The use of these fuels is expected to decline for two important reasons: limited global oil reserves and their negative impact on the environment. In addition, the gases emitted by petroleum-fueled vehicles have an adverse effect on the environment and human health. The need to reduce these emissions is universally supported. In view of this, scientists are now faced with the problem of simultaneously achieving maximum fuel efficiency and minimum pollutant emissions by using non-petroleum alternative fuels for internal combustion engines. Alternative fuels have received considerable attention, and much research works have been conducted to identify alternative energy sources and techniques allowing their utilization in compression ignition engines. One of the most promising options is the dual-fuel engine with natural gas as the primary fuel since natural gas is of great interest as a clean alternative fuel. Dual-fuel operation is an interesting technique for using this fuel in compression ignition engines, both economically and environmentally. This technique shows promising results in terms of nitrogen oxides (NOx) and particulate matter (PM) emissions. However, the use of alternative fuels has some disadvantages such as reduced thermal efficiency of the engine, increased carbon monoxide (CO) and total unburned hydrocarbons (THC), especially at low load condition. The main objective of this research is to address the challenges associated with dual-fuel natural gas engines in order to improve engine efficiency and achieve better exhaust emission control. Two approaches were used to improve this mode of operation; the first is mainly based on an experimental investigation where the effect of natural gas enrichment with different levels of hydrogen concentration on the combustion and exhaust emissions of a dual-fuel engine was studied. Then, the effect of the pilot injection strategy was examined. The second approach is a numerical study, since the combustion is very complex; parameters such as temperature field, air-fuel ratio distributions and emission locations are not completely understood using experimental data. Therefore, a numerical simulation was developed to obtain a better understanding of the combustion process. It was also utilized to study the effect of the piton bowl shape