Spray, ignition and combustion characteristics of biodiesel and diesel fuels injected by micro-hole nozzle under ultra-high injection pressure

The spray and combustion characteristics of biodiesel (BDF) and diesel fuels injected by a micro-hole nozzle of 0.08 mm diameter under increasing injection pressure up to ultra-high value of 300 MPa were investigated in this research. The LIF-PIV (Laser Induced Fluorescence- Particle Image Velocimetry) technique was used to investigate the spray and entrained gas characteristics of the fuels while the OH chemiluminescence and two color techniques were utilized to study the ignition and combustion characteristics of the spray flames. From the research it was observed that at all injection pressures, due to inferior atomization processes, the normal velocity and total mass of the entrained gas by BDF was less compared to diesel. As a result of higher cetane number the BDF's flame ignition delay was shorter compared to diesel. The ratio of the mass flow rate of gas entrained to mass flow rate of injected fuel by BDF was less compared to diesel. Oxygen content in the BDF played a greater role in soot reduction as against the gas entrained.