Microemulsion fuels for compression ignition engines: A review on engine performance and emission characteristics

Abstract Fossil fuels are currently the world’s primary source of energy. Their limited reserves and increasing emissions have, however, generated an interest in the development of renewable and cleaner alternative sources of energy. Compression ignition (CI) engine is an extensively used internal combustion engine, with a better fuel economy and efficiency as compared to spark ignition (SI) engine. Particulate matter (PM) and NOx emissions generated from diesel fuel are serious environmental and health concerns, which also have led to an interest in the diesel alternatives. Most commonly used diesel alternatives are either uneconomical or require modifications in current engine and infrastructure. Microemulsification is a developing technique, which is economical and does not require any changes in the current systems. In this review, we have focused our attention on diesel, vegetable oil, and alcohol based microemulsion fuels as an alternative to diesel for the CI engines. While most of the microemulsions have lower calorific values and higher fuel consumptions, the thermal efficiency is improved due to the presence of water. Moreover, it helps in the simultaneous reduction of PM and NOx emissions. Considering the trends in the costs of fossil fuels in recent past and present, microemulsions seem to be most promising, cleaner, and powerful alternative to fossil fuels, such as gasoline, diesel and aviation fuels.