Development of Oxygenated Diesel Fuel and Impact on Vehicle Performance

World is moving towards cleaner, greener and energy efficient fuels.

The rapid increase in the consumption of petroleum fuel has led to twin problem of air pollution and energy security. India being a developing nation, fuel demand and consumption in various industries, especially in road transport sector has been rising continuously. Fossil fuels are the main source of energy and approximately 85% of domestic need met through import of crude oil. The increasing fuel consumption has created interest for the blending of biofuels in conventional fuel and renewable fuels also. Among biofuels ethanol is one of them and preferable choice for blending in gasoline which is a fuel for spark ignition engines and flex fuel vehicles. As such ethanol/methanol cannot be used in compression-ignition diesel engines without engine modifications due to inherent low cetane number and lubricity of alcohols. Therefore, fuel consisting of certain concentrations of alcohols such as methanol/ethanol in diesel blends is being promoted.

The lower alcohols (methanol/ethanol) are not miscible in diesel due to their polarity differences. An additive package is essential for the solubility and stability of alcohol (methanol/ethanol) in diesel phase or diesel blends. Since diesel fuel pumps operate at much higher pressure (up to 220MPa in high-pressure diesel fuel pumps) than the gasoline pumps, oxygenated diesel blends must impart adequate lubricity to metallic parts of fuel delivery system and engine. Lubricity is the one of the important property of diesel specifications (IS: 1460-2017) and appropriate dosing of additive package is compulsory to maintain the specifications of oxygenated diesel blends / alcohol-diesel blends. To tackle the low cetane number, lubricity issue and stability of alcohol-diesel blends, suitable chemistry and dosage of additive package was optimized. Fuel properties of conventional diesel vis-a-vis oxygenated diesel blends having methanol/ethanol up to 15% (v/v) along with appropriate additive package comprising of lubricity improver (LI), cetane improver (CI) and corrosion inhibitor were studied. In this paper, the detailed critical properties of conventional diesel versus oxygenated diesel blends are discussed.