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Concern about the depletion of petroleum reserves, rising prices of conventional fuels, security of supply and global warming have driven research toward the development of renewable fuels for use in diesel engines. These fuels have different physical and chemical properties that affect the diesel combustion process. This paper compares between the autoignition, combustion, performance and emissions of soy-bean derived biodiesel, Jet propellant (JP-8) and ultra low sulfur diesel (ULSD) in a high speed single-cylinder research diesel engine equipped with a common rail injection system. Tests were conducted at steady state conditions at different injection pressures ranging from 600 bar to 1200 bar. The ‘rate of heat release’ traces are analyzed to determine the effect of fuel properties on the ignition delay, premixed combustion fraction and mixing and diffusion controlled combustion fractions. Biodiesel produced the largest diffusion controlled combustion fraction at all injection pressures compared to ULSD and JP-8. At 600 bar injection pressure, the diffusion controlled combustion fraction for biodiesel was 53% whereas both JP-8 and ULSD produced 39%. In addition, the effect of fuel properties on engine performance, fuel economy, and engine-out emissions is determined. On an average JP-8 produced 3% higher thermal efficiency than ULSD. Special attention is given to the oxides of nitrogen (NOx) emissions and particulate matter characteristics. On an average biodiesel produced 37% less NOx emissions compared to ULSD and JP-8.

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JP-8 is being closely watched as a suitable fuel for the “One fuel policy” by US Army. Some of the main targets of Army in the battle are the fuel economy and smoke/soot emissions. Soot emissions can be reduced in two ways, by increasing the injection pressure or by increasing swirl. An investigation was conducted to find out the more effective way to reduce soot emissions and to evaluate the influence of the swirl motion on JP-8 fuel combustion, performance and emissions in a single cylinder diesel engine. Increasing swirl increased heat losses and produced lower temperatures during injection process. Increasing swirl improved the premixed combustion fraction and produced higher peak temperatures and in turn increased NOx emissions. Increasing swirl also increased the nano-particle emissions.

An investigation was conducted on a 0.42 liter single cylinder diesel engine equipped with a common rail fuel injection system to evaluate the influence of the swirl motion on JP-8 fuel combustion. Engine tests were performed under steady state conditions of 5 bar IMEP and 1500 RPM. Two different swirl ratios of 1.44 and 7.12 were applied at injection pressures ranging from 400 to 1200 bar. The apparent rate of heat release (ARHR) curve is analyzed to determine the effect of swirl on combustible mixture formation, auto-ignition, premixed and diffusion controlled combustion fractions. An attempt is made to correlate between the swirl ratio and different combustion and emissions parameters at different injection pressures. The emissions included the gaseous fractions and particulates. Two types of particulate matter were measured: Accumulation mode particles (AMPs) and Nucleation mode particles (NMPs). The results indicate that ignition delay duration of JP-8 increases as the swirl ratio increases influencing the overall combustion process and engine out emissions.