Performance and Emission Characteristics of CI Engine Fueled by Coconut Oil Methyl Ester

Neat vegetable oils pose some problems when subjected to prolonged usage in CI engine. These problems are attributed to high viscosity, low volatility and polyunsaturated character of the neat vegetable oils. These problems are reduced to minimum by subjecting the vegetable oils to the process of transesterification. Biodiesel is a non-toxic, biodegradable and renewable fuel with the potential to reduce engine exhaust emissions. The methyl ester of coconut oil, known as biodiesel, is receiving increasing attention as an alternative fuel for diesel engines. The biodiesel is obtained through transesterification process. Transesterification is the process of using an alcohol, ethanol or methanol, in the presence of a catalyst, such as sodium hydroxide or potassium hydroxide, to chemically break the molecule of the oil or fat into an ester and glycerol. The coconut oil methyl ester (or biodiesel) was prepared from coconut oil through transesterification process using methanol and sodium hydroxide. Various properties of the biodiesel thus developed are evaluated and compared in relation to that of conventional diesel oil. Neat biodiesel has almost similar density and viscosity to that of diesel. Neat biodiesel was miscible in any proportion with that of mineral diesel oil. The flash point of biodiesel is high thus biodiesel is an extremely safe fuel to handle as compared to diesel oil. The calorific value of biodiesel is less than diesel fuel as it is oxygenated fuel.

In the present investigation neat coconut oil methyl ester (CME) as well as the blends of varying proportions of coconut oil methyl ester (CME) and diesel were used to run a CI engine. A 661 CC Kiloskar make TV1 single cylinder 4-Stroke water-cooled diesel engine having compression ratio of 17.5: 1 and developing 5.2 kW at 1500 rpm was used. Significant improvements in engine performance and emission characteristics were observed. The addition of coconut methyl ester (CME) to diesel fuel has significantly reduced HC and smoke emissions. The similar brake thermal efficiency and BSEC was observed. The cylinder gas pressure and the exhaust gas temperature produced during biodiesel operation were similar to diesel operation.