PERFORMANCE AND EMISSION CHARACTERISTICS OF A DIESEL ENGINE FUELED BY RAPESEED OIL BIO-FUEL

Abstract

This study had used straight vegetable oil (SVO) particularly neat rapeseed oil as a fuel in a direct injection diesel engine. Combustion performance and exhaust emissions of using the fuel have been measured from no load up to full load engine condition. For comparison diesel fuel JIS#2 have been used. SVO gives higher NOx but lower smoke emissions at high load compared with JIS#2. Lower smoke emissions at high load is due to oxygen content in the SVO that can eliminate partially unburned fuel at stratified fuel rich zone during combustion. Enhanced combustion raises the temperature inside the combustion chamber and caused higher NOx emission. In addition of using SVO as fuel, this study also had blend several percentages of ethanol into SVO with the presence of octanol as surfactant. As percentage of ethanol increased in this SVO-ethanol blend, smoke and particulate emissions reduced with unchanged NOx level. This is because the reduction of kinematic viscosity of SVO-ethanol blend improves the atomization and vaporization of injected fuel droplets that leads to lower particulate emission. Simultaneous reduction of NOx and particulate emissions can be obtained by transform the SVO into an emulsion fuel by blending some percentages of water into SVO with existence of castor oil as surfactant. Evaporation of water during combustion reduces the combustion temperature and causes the reduction of NOx emission. Reduction of particulate emission is due to water gas reaction. However, the use of SVO emulsion in diesel engine shows deterioration of CO and THC emissions.