A comprehensive review on water-emulsified diesel fuel: chemistry, engine performance and exhaust emissions

Increasing environmental concern, human health and the continuous upgradation in the stringent standards of vehicular emissions have shown much interest in cleaner diesel fuels. Out of various strategies to mitigate the diesel engine emissions, use of water blended diesel in the form of emulsion has grabbed sufficient attention of the fuel research community. Various researches have shown that water-emulsified diesel has sufficient potential to improve the engine performance simultaneously with a significant reduction in the levels of nitrogen oxides (NO_x) and particulate matter (PM) emissions. Micro-explosion phenomenon of combustion in emulsion fuel helps to provide efficient and complete combustion which in turn improves brake thermal efficiency. The current study presents a comprehensive review of the usage of water-emulsified diesel fuel in CI engines. Focusing on the performance, combustion, and emission analysis, it also talks in detail about the principle and the chemistry involved in making of a stable and homogeneous water-diesel emulsion compatible for CI engine. The literature survey concludes two crucial points. First, the water-blended diesel emulsion serves as an economical, fuel efficient, and cleaner combustion technology. Second, the optimum blend ratio, emulsifier quantity, and proper process differs in almost all the research papers and hence needed to be standardized.