Performance and Emission Studies of a Compression Ignition Engine on blends of Calophyllum Oil and Diesel.

Abstract

In the present scenario of energy crisis and global warming, the use of eco-friendly renewable fuels is gaining worldwide attention. Amongst the variety of such fuels, biofuels from energy crops form an important solution. In this context, fuels derived from non-edible vegetable oil have a major role to provide energy security and mitigate environmental degradation. Despite extensive work carried out by large number of researchers, a huge number of non-edible vegetable oils are yet to be explored as a feedstock for small energy requirements. So, there is an urgent need to assess the potential of such underutilised feed stocks. It has been found that chemical processing of vegetable oil should be carried to bring out its properties similar to diesel fuel. However, the chemical processing requires capital investment and technical experience, which is not feasible in rural areas. Therefore, the vegetable oil in neat form without any chemical treatment presents a sustainable solution. The present study aims at evaluation of one such underutilised species ‘Calophyllum’. This plant is abundantly available in coastal India, Bangladesh, South America, African coast and Australia. The oil in raw form and blended with diesel (10% and 20% by volume) were used to fuel a single-cylinder diesel engine, and the results compared with baseline data of diesel. The results suggest a reduction of 6.97 and 12.4% in brake thermal efficiency (BTE) on 10 and 20% blends, respectively, as compared to mineral diesel operation. Further brake-specific energy consumption (BSEC) was found to increase by 7.35% for 10% blend and by 14.03% for 20% blend. This reduction in BTE is compensated by the fact that carbon monoxide (CO) emission is reduced by 25% at full load with 10% blend, and around 50% with 20% blend, suggesting better combustion. The nitrogen oxide (NOx) emissions were found to be reduced by 13.48% at full load with 10% blend, and by 25.24% with 20% blend. Unburnt hydrocarbon (UBHC) emissions at peak load were increased by 9.1% at 10% blend, as compared to baseline. At 20% blend, the UBHC emissions were found to be further increased by 18%, compared to the neat diesel operation. The UBHC emissions are lower at partial loads, but tend to increase at higher loads for all fuels. This is due to the lack of oxygen, which is caused by engine operation at a higher equivalence ratio. On the basis of exhaustive experimental work, it can be concluded that 10% blend of Calophyllum oil with diesel in unmodified diesel engine may roughly decrease CO emissions by 12% and NOx by 25%, whereas UBHC is increased by 9%, at the penalty of 5% reduction in BTE and 8% increase of BSEC.