Effect of Fuel Injection Timing in the Combustion of Biofuels in a Diesel Engine

Abstract

Methyl and ethyl esters of vegetable oils have become an important source of renewable energy with convenient applications in traditional compression ignition engines. Previous studies have indicated that some advantages exist with the use of these biofuels, such as the reduction of CO, particulate matter and unburned hydrocarbons in the emissions. On the other hand, the main disadvantage in the use of these biofuels is the increase of nitrogen oxides (NOx) emissions due to differences in chemical composition and physical properties of the biofuel, which in turn affect engine operational parameters such as injection delay and ignition characteristics, compared to petroleum-based diesel. The effects of fuel injection timing, which can compensate for these changes, on the performance and emissions in a single cylinder air-cooled diesel engine using canola methyl ester and its blends with diesel are presented in this study. The engine is a single cylinder, four stroke, naturally aspirated, CI engine with a displacement volume of 280 cm rated at 5 HP @ 3600 rpm under a dynamometer load. It was equipped with a pressure sensor in the combustion chamber, a needle lift sensor in the fuel injector and a crank angle sensor attached to the crankshaft. Additionally, the temperature of the exhaust gases was monitored using a thermocouple inside the exhaust pipe. Pollutant emissions were measured using an automotive exhaust gas analyzer. Advanced, manufacturer-specified standard, and delayed injection settings were applied by placing shims of different thicknesses under the injection pump, hence, altering the time at which the high pressure fuel reached the chamber. The start of injection was found to be insensitive to the use of biofuels in the engine. The late injection timing of the engine provides advantages in the CO and NO emissions with a small penalty in fuel consumption and thermal efficiency.