VOL. 4, NO. 9, NOVEMBER 2009 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2009 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com THE PERFORMANCE AND EMISSIONS OF A VARIABLE COMPRESSION RATIO DIESEL ENGINE FUELLED WITH BIO-DIESEL FROM COTTON SEED OIL R. Anand 1 , G. R. Kannan 1 , K. Rajasekhar Reddy 1 and S. Velmathi 2 1 Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamilnadu, India 2 Department of Chemistry, National Institute of Technology, Tiruchirappalli, Tamilnadu, India E-Mail: anandachu@nitt.edu ABSTRACT A methyl ester of cottonseed oil was prepared and blended with diesel in four different compositions varying from 5% to 20% in steps of 5%. Tests were conducted in a single cylinder variable compression ratio diesel engine at a constant speed of 1500 rpm. Highest brake thermal efficiency and lowest specific fuel consumption were observed for 5% biodiesel blend for compression ratio of 15 and 17 and 20% biodiesel blend for compression ratio of 19. The 20% biodiesel blend at a compression ratio of 17 had maximum nitric oxide emission as 205 ppm, while it was 155 ppm for diesel. Substantial reduction in Carbon monoxide emissions and smoke in the full range of compression ratio and loads was observed. Improved heat release characteristics were observed for the prepared biodiesels. The results reveal that the biodiesels can be used safely without any modification to the engine. Keywords: cotton seed oil, biodiesel, emission, combustion, compression ratio. INTRODUCTION India is the second largest producer of cotton seed in the world next to china with the potential of 4.6 million tonnes of oil seeds per annum. With the rapid development of rural agricultural production and rapid growth of local industry in India, the discrepancy between demand and supply of energy has become an increasingly acute problem. Due to seasonality of farm work, a temporary shortage of fuel will bring about unexpected and irreparable loss to peasants. The limited (and fast diminishing) resources of fossil fuels, increasing prices of crude oil, and environmental concerns have been the diverse reasons for exploring the use of vegetable oils as alternative to diesel oil [1-4]. Vegetable oils offer almost the same output with slightly lower thermal efficiency when used in diesel engines [5-7]. Reduction of engine emissions is a major research aspect in engine development with the increasing concern over environmental protection and the stringent exhaust gas regulation [8-13]. The use of neat vegetable oils poses some problems when subjected to prolonged usage in CI engines. These problems are attributed to high viscosity, low volatility and polyunsaturated character of vegetable oils [14-17]. Some of the common problems posed by using vegetable oils in diesel engines are coking and trumpet formation on the injectors, carbon deposits, oil ring sticking and thickening and gelling of lubricating oil as a result of contamination by the vegetable oils [18-20]. Different methods such as preheating, blending and transesterification [21-25] are being used to reduce the viscosity and to produce bio-diesel, suitable for engine applications. In the present investigation, bio-diesel is prepared from cotton seed oil. The fuel properties of the synthesized bio-diesel were determined and their performance, emission and combustion characteristics were studied on a four-stroke, single cylinder, variable compression ratio direct-injection diesel engine to ensure their suitability as CI engine fuel. EXPERIMENTAL SYSTEM DEVELOPMENT FOR BIO-DIESEL FORMULATION METHODOLOGY The raw cotton seed oil was extracted by mechanical expeller in which small traces of organic matter, water and other impurities were present. Transesterification is a most common and well established chemical reaction in which alcohol reacts with triglycerides of fatty acids (vegetable oil) in presence of catalyst to form glycerol and esters [1- 3, 10, 17, 22-23]. The reaction is shown in Figure-1. Experiments were conducted in a laboratory setup consisting of heating mantle, reaction flask (made of glass), separating funnel and mechanical stirrer. A round bottom flask of 2 litre was used as laboratory scale reactor for the present analysis. It consisted of three necks. One for stirrer, the others for condenser and inlet of reactants, as well as for placing the thermocouple to observe the reaction temperature. The flask has a stopcock at the bottom for collection of the final product. The progress of the reaction was observed by measuring the acid value. In the course of the test, it was observed that the appropriate quality of bio-diesel could be produced from cotton seed oil in both acid catalyst esterification and alkaline catalyst esterification. 72