Effect of Butanol Addition to Neem Biodiesel-Diesel Blend on Emission Characteristics of Diesel Engine

Abstract

The effect of butanol addition in biodiesel-diesel blend to ascertain the emission characteristics of diesel engine was investigated. Experiments were carried out on a four-stroke, single cylinder, air-cooled compression ignition engine. A blend of neem biodiesel 20% and diesel fuel 80% was prepared and labelled as B20. Butanol was then added to B20 blend at volume percent of 5%, 10% and 15% which was labelled as B20Bu5, B20Bu10 and B20Bu15 respectively. These samples were tested on the engine at two conditions: firstly, when speed was constant (2600 rpm) with varying torque of 4, 6, 8, 10 and 11 Nm, and secondly when torque was constant (4 Nm) with varying speed of 2000, 2200, 2400 and 2600 rpm. Exhaust gas analyzer was used to measure exhaust emissions such as nitric oxide (NO), carbon dioxide (CO2), carbon monoxide (CO) and unburnt hydrocarbon (HC). The result shows that B20 blend has the highest amount of NO emission at all engine loads. At varying speed B20 blend was found to have NO emission of 303.8 ppm on average but the addition of butanol to B20 blend significantly reduced the amount of NO emission by 16%. NO emission reduced much with more percentage of butanol in the blend. In regards to CO₂ emission, it was found that blends containing butanol emits higher amount of CO₂ than B20 blend. However, CO₂ emission decreased as percentage of butanol in the blend increase. At constant speed B20 blend increases CO emission more than blends containing butanol while at varying speed the result shows very insignificant difference. It was also revealed that blends containing butanol releases higher HC emissions than B20 blend across all engine speeds. At varying torque B20 blend emits higher HC than blends with butanol except for B20Bu15 which has 16.4 ppm on average. A regression equation was developed in order to predict the exhaust emissions at specific engine conditions using a particular fuel blend.

Keywords: Butanol, neem-biodiesel-diesel, emissions and predictive equation