Experimental Investigation of Neem Oil Methyl Ester and its Blends with Diesel as an Alternative Fuel for a DI Diesel Engine

Abstract

Vegetable oils offer almost the same power output with slightly lower thermal efficiency when used in diesel engines. Neem oil being non-edible could be regarded as an alternative fuel for compression ignition engines. Vegetable oils like neem oil are available in rural areas and have high cetane number and calorific value quite close to that of diesel fuel. The uses of any vegetable oils have some problems when subjected to prolonged usage in diesel engines. The problems are attributed to high viscosity, low volatility and poly unsaturated character of neat vegetable oils. Higher viscosity of vegetable oils causes improper atomization of fuels during injection and result in incomplete combustion. The viscosity of neem oil is reduced by transesterification to obtain neem oil methyl ester. Application of bio-fuel derived through trans-esterification of Neem oil is prevalent in diesel engines since it has fuel economy and reduction of emission of exhaust gases. In the present study necessary efforts have been made to prepare a bio-fuel through trans-esterification from raw neem oil to study the performance, combustion analysis and emission characteristics.  The derived fuel called “NEEM OIL METHYL ESTER” (NOME-C17H34COOCH3) has been used in a single cylinder water cooled diesel engine under standard operating conditions. The experimental investigations were carried out to assess the combustion analysis, performance and emission levels of the engine using NOME and its blends with diesel.  The brake thermal efficiency of NOME is found to be much higher than diesel due to improved combustion lubricity and reduced friction.  The NOx level, the exhaust gas temperature and HC for NOME are found to be higher than diesel due to efficient combustion, lower viscosity and good mixture formation.  The smoke is also found to be lower than diesel, because of excess oxygen present in the bio-diesel.  Under combustion analysis heat release rate, rate of pressure rise, and cylinder pressure were calculated, plotted and curves were drawn for diesel fuel, NOME and its blends with diesel and compared with diesel fuel. The heat release rate is slightly higher for NOME compared to diesel because of better premixed combustion and increases NOX emissions. Adiabatic flame temperatures were also calculated for NOME and its blends with diesel. The adiabatic flame temperature is reduced drastically with excess air for diesel, NOME, B20 and B30.  It is found that adiabatic flame temperature of B20 is close to diesel.