Abstract:

Biodiesel, which commonly refers to fat acid methyl esters made from vegetable oils or animal fats, is a kind of ideal alternative fuel for diesel engines. Compared to pure petroleum diesel fuel, biodiesel has higher cetane number, including oxygen, higher viscosity, lower heating value, almost no aromatic hydrocarbon and sulfur. This leads to different fuel injection and spray properties, combustion characteristic, power and fuel consumption, exhaust emissions from petroleum diesel fuel. Compared to pure petroleum diesel fuel, biodiesel has earlier fuel injection timing, longer spray penetration and smaller spray angle, and shorter ignition delay. Diesel engines have lower mass of CO, HC, smoke, and particulate matter (PM) emissions when using biodiesel, and the reduction percentages are proportional to blend ratios of biodiesel fuel. But NOx , aldehyde and ketones emission have slightly increase, as well as number concentration of nucleation mode particles. High pressure common rail fuel injection system and exhaust gas after-treatment technology for biodiesel are important directions in future.

Key words: diesel engine, biodiesel, fuel injection, combustion, emission