Auto-ignition, combustion and emission characteristics of soybean biodiesel, Jet Propellant (JP-8) fuel and ultra low sulfur diesel in a single cylinder diesel engine

Concerns about the depletion of petroleum reserves, rising prices of conventional fuels and ill-effect of vehicular emissions on human health have driven research toward the development of alternate fuels like biodiesels and Jet propellant fuels for use in diesel engines. The use of biodiesel in diesel engines is motivated by aspirations to find suitable future substitute, whereas Jet Propellant (JP-8) fuel is currently used by US army on its combat vehicle fleet as a substitute to diesel to simplify the logistic supply chain for petroleum products in war zones. Though the topic of 'diesel fuel combustion' has been extensively investigated by scientific community, there is need to further understand the combustion mechanism of biodiesel and JP-8 fuel.This thesis presents results of series of investigations conducted on a 0.42 liter, single cylinder diesel engine to evaluate the influence of the auto-ignition and combustion characteristics of a fuel on engine performance and engine out emissions. The engine is equipped with a common rail fuel injection system. Three different fuels - Soybean biodiesel, JP-8 fuel and ultra low sulfur diesel were used. Tests were conducted at steady state conditions at different injection pressures ranging from 600 bar to 1200 bar. The 'rate of heat release' traces were analyzed to determine the effect of fuel properties on the ignition delay, premixed combustion fraction and diffusion controlled combustion fractions. Also, an effort is made to analyze and compare engine out emissions such as HC,CO,NOx and particulate matter.The results indicate that the physical and chemical properties of fuel had a significant impact on the combustion process, affecting the overall engine performance and emissions. It was concluded that fuel volatility has a considerable effect on rate of fuel evaporation and mixture formation, whereas aromatics, sulfur and O2 content of a fuel influence the NOx and particulate formation in diesel engine.