A diesel engine study of conventional and alternative diesel and jet fuels: Ignition and emissions characteristics

• In-cylinder ignition delay decreases with increasing DCN, 15% for DCN from 40 to 80.
• BSFC and CO and NO emissions are lower for hydroprocessed and F-T fuels.
• Fuel consumption and CO emission are correlated and decrease with increasing DCN.
• NO emissions are correlated and decrease with increasing H/C.

Measurements of ignition delay, CO and NO emissions, and fuel consumption were carried out in a light-duty single-cylinder direct-injection diesel engine for operation with petroleum and alternative hydroprocessed and Fischer–Tropsch diesel and jet fuels. Ignition measurements carried out for a fixed engine speed and injection timing quantify the decrease in in-cylinder ignition delay with increasing derived cetane number (DCN) over a range of DCN relevant to diesel engine operation (DCN = 40–80) and show no discernible dependence of ignition delay on other fuel properties. Brake specific fuel consumption (BSFC) was found to decrease with increasing DCN with strong correlation due to a reduction in ignition time for fixed-injection-timed operation. Brake specific CO emissions were also found to decrease with increasing DCN due to increased time provided for CO burn out due to earlier ignition. Brake specific NO emissions were found to decrease with increasing hydrogen-to-carbon (H/C) ratio, due to the lower peak combustion temperatures and thermal NOx occurring for fuels with higher H/C.