Engine Emissions and Performance using WCO Biodiesel

Abstract

Combustion performance and exhaust emissions from the combustion of biodiesel made from waste cooking oil (WCO) are presented in this paper. Several solutions for alternative fuels particularly to substitute petroleum/fossil fuels in transport sector are available. Waste cooking oil (WCO) is one such option already used in certain ratios in the US, EU and other countries but there are still some issues relating to running diesel engines on WCO due to differences in the chemical composition between biodiesel and diesel. In order to gather more information of the overall performance in engines and emission formation, experimental tests were conducted and comparisons were made with the petroleum diesel. Elemental analysis of WCO biodiesel confirmed that different functional groups, lead to major differences in the combustion characteristics of the two fuel types. The biodiesel found to have 10% lower carbon content, almost no Sulphur content and up to 12%, more oxygen content compared with diesel. Higher oxygen content and double bonds in WCO biodiesel increase its susceptibility to oxidation and explains up to l8% lower caloric value and up to 9% lower engine torque compared with diesel. Using WCO blends ratio up to 75% in diesel showed a reduction in exhaust emissions compared with diesel. The brake specific fuel consumption (BSFC) increases as the biodiesel blend ratio in diesel increases due to greater mass of fuel being injected at a given injection pressure, compared with diesel. A common conclusion can be made in favor of the WCO biodiesel as being a greener alternative to petro-diesel when used in blend with diesel. Large variations in the feedstock used for biodiesel production would lead to variations in the physical and chemical properties of the WCO biodiesel produced. Stringent standards may need to be imposed for biodiesel quality in order to reduce the effect of variation in physiochemical properties on engine performance and emissions. However, experimental tests confirmed that biodiesel-diesel blends could be used in current diesel engines without loss of performance.