Combustion and Emission Characteristics of a Diesel Engine Fuelled with Diesel-LPG Blends

Recently, it has been worth pointing out the relevance of alternative fuels in the improvement of air quality conditions and in the mitigation of global warming. In order to deal with these demands, in recent studies, it has been considered a great variety of alternative fuels. It goes without saying that the alternative fuels industry needs the best of the efficiency with a moderate layout. From this perspective, Liquefied Petroleum Gas (LPG) could represent a valid option, although it is not a renewable fuel. In terms of polluting emissions, the LPG can reduce nitrous oxides and smoke concentrations in the air, a capability that has a relevant importance for the modern pollution legislation. LPG is well known as an alternative fuel for Spark Ignition (SI) engines and, more recently, LPG systems have also been introduced in the Compression Ignition (CI) engines in dual-fuel configuration. In this research, LPG-Diesel liquid-blend has been used to power a CI engine in mixed fuel configuration. For this purpose, accurate modifications have been made on the single cylinder test ring and on the standard rail fuel injection system. LPG has been blended with diesel on the basis of the ratio 20-35% w/w. During the study, they have been carried out three sets of measurements: one by only using Diesel fuel and the others by using blended fuels at different engine operating conditions. The thermodynamic process, the combustion performance, and the exhaust emissions have been analyzed thanks to a specific designed-test campaign, with particular attention to the control strategies of fuel injection. The results show that, at partial load operating condition, Diesel-LPG blends improve the combustion and emission performances. In particular, it has been noticed, at constant Nitrogen Oxide (NOx), a significant decrease of particulate emissions. This observation confirms the previous authors' results achieved on the optical engines.