Optimization of the Compression Ratio of a Diesel Engine Running on Croton Bio-diesel

Abstract

Over the past few decades, there has been growing concerns over the sustainability of petroleum derived fuels. Approximately 86.4 percent of the world depends on fossil fuel as their primary energy source. Numerous researches have found that fossil fuels are being depleted very rapidly and will be completely depleted in the near future. With no alternative energy source to the major fuel in the world, there will be the largest energy crisis ever experienced. Due to this, researchers all over the world are in constant search for alternative fuels that are renewable, sustainable, readily available and which can easily replace petroleum fuels. In Eastern Africa, one such potential renewable fuel source is the croton megalocarpus plant, which widely grows in the highlands of Eastern and Southern Africa. A number of previous studies have identified croton seed bio-diesel as a very promising fuel that can substitute diesel fuel in an internal combustion without any major modifications on the engine. However, most of these studies have focused more on the properties of the bio-diesel rather than on its performance in an engine. Sivaramakrishnan studied Karanja biodiesel and found that a blend of B20 and compression ratio of 18 had even better performance than diesel fuel. Muralidharan and Vasudevan studied waste vegetable oil and found out that a blend of B40 had almost similar performance and lower emissions when compared to diesel fuel at higher compression ratios. Similar studies have also been done on other renewable fuel sources such as Jatropha and palm oil. The aim of this study was to analyse the performance, combustion and emission characteristics of a variable compression ratio CI engine running on croton bio-diesel. Extensive research has shown that croton is relatively unexplored as a bio-diesel. Tests were done on blends of the bio-diesel (B0, B20, B40, B60, B80 and B100) at compression ratios of 12, 14, 16 and 18. The performance characteristics to be considered included brake thermal efficiency, specific fuel consumption (SFC), brake thermal efficiency and brake mean effective pressure (BMEP). Combustion parameters to be considered included the mass fraction burnt, net heat release and mean gas temperature. From the results of the study, croton bio-diesel can be used in a diesel engine without any major modifications. The greatest challenge identified was the viscosity of the bio-diesel, which effects the rate of the combustion process. As the compression ratio was increased from 12 to 18, the performance of the engine also increased. A blend of B20 has the best performance, with almost the same brake power as that of diesel fuel and a higher rate of heat release."