Practice of diesel fuel blends using alternative fuels: A review

In order to meet the growing global energy requirement, exhaustive research is carried to develop and to use variety of renewable fuels. Concerns on the long-term availability of petroleum diesel and the stringent environmental norms have mandated the search for a renewable alternative to diesel fuel to address these problems. Diesel engines have proven their utility in the transportation, agriculture, and power sectors for small energy needs as a potential source of decentralized energy generation for electrification. Mixing of diesel fuel with biodiesel has been considered as good alternative to diesel in the past couple of years. The objective of the present study is to compare the performance, emissions and combustion characteristics of blended fuels in the unmodified diesel engine. Differences in the fuel properties of non-edible vegetable oils, biodiesels and other diesel fuel blends are considered in this review. Various diesel fuel blends with di-ethyl ether, ethyl-tert-butyl ether, mono-ethylene glycol ethyl ether, mono-ethylene glycol butyl ether, diethylene glycol ethyl ether, cottonseed oil, jatropha oil, karanja oil, mahua oil, linseed oil, rubber seed oil, neem oil, cashew nut shell oil, marine gas oil, fish oil, were used in diesel engine operation and their results were analyzed. It is clear from this review that all the blends studied generally causes an increase in NOx emission and a decrease in HC, CO and PM emissions compared to diesel. Biodiesel blended fuel shows lower brake thermal efficiency and slight increase in its brake specific fuel consumption compared to conventional diesel for the same energy output. Result of combustion and performance characteristics shows that biodiesels from different origin and its blends with diesel at 10-20% is better than higher blends. Thus, biodiesel could be a potential fuel for diesel engine and play a vital role in the near future especially for small and medium energy requirements. Hence, use of 10% to 20% blend of biodiesel is favorable for long term application in diesel engines, considering performance and emissions characteristics which are close to mineral diesel.