A Study on the Applicability of Straight Vegetable Oils to Medium Speed Diesel Engines

Straight vegetable oil (SVO) fuels such as palm oil, animal fat oil and waste vegetable oil were tested as fuels in a single-cylinder diesel engine to evaluate applicability to medium-speed diesel engines. Fuel-related properties of the SVO were assessed and compared with conventional marine diesel fuel oil (MDO). The total acid number (TAN) of the SVO fuels changed during a short interval in a drying oven which heated the SVO fuels to 170 degrees Celsius for several weeks. The SVO have not gone rancid any further after reaching limit. And the TAN of the SVO fuels was not related to corrosion of the parts. The SVO fuels needed to be heated to an appropriate temperature to use as fuel of the engine since the SVO fuels are more viscous than conventional diesel fuels. Both the injection period and the injection pressure increased due to low heating values of the SVO fuels. By the same token, fuel oil consumption increased over 10%. The overall exhaust emissions were lower with the SVO fuels, but NOx emission was as much as MDO at the higher loads.