Author : Alireza Valipour

The liquid alternative fuels discussed in the present work include alcohol fuels such as ethanol, butanol and methanol, neat vegetable oils and biodiesel fuels. From the review, it is observed that the emissions pollutants (HC, CO, NOx and PM) are typically the same or lower with regards to ethanol fuels than conventional diesel fuel. Methanol contains oxygen in its chemical structure; hence less air is required for complete combustion. This is the reason for reduced CO2 emissions from motor vehicles using methanol/diesel blends. However, this could also increase NO x. The previous studies revealed the beneficial effects of using various blends of n-butanol with diesel fuel on smoke and CO emissions at various loads, however at the expense of higher NOx and HC emissions. Again, it is the high oxygen content of n-butanol that leads to enhanced in-cylinder soot oxidation, which is responsible for the decrease in smoke emissions. The combustion of straight vegetable oil (SVO) in internal combustion engines has shown conflicting results in emissions. Vegetable oils with high percentages of fully saturated fatty acids have the potential to produce lower NOx emissions. The reported value of oxides of nitrogen emission from biodiesels were higher as compare to diesel, whereas the carbon monoxide, hydrocarbon, and smoke emission of biodiesel fuels are lower than diesel. From the review, it is observed that the combustion characteristics of biodiesel are almost similar to that of diesel and slightly inferior performance as compared to diesel.

Keywords: Biodiesel, Vegetable Oil, Alcohol Fuel, Carbon Monoxide, Nitrogen Oxide, Hydrocarbon, Smoke

Article published in International Journal of Current  Engineering  and Technology, Vol.4,No.1 (Feb- 2014)