Experimental Investigation on Life Cycle Analysis and Combustion Characteristics of CI Engine Operating on Bio-Diesel with Additives

Abstract

Petroleum based fuels play a vital role in rapid depletion of conventional energy sources along with increasing demand and also major contributors of air pollution. Major portion of today's energy demand is being met with fossil fuels. The gradual reduction of world petroleum reserves, growths in prices of petroleum based fuels and the exhaust created by engine emissions have heartened studies to search for unconventional fuels. As India is an agricultural country, there is a wide scope for the production of vegetable oils (both edible and non-edible) from different oil seeds. Hence, it is high time that alternate fuels for engines should be derived from indigenous sources. Bio-diesel derived from vegetable oil is an unconventional diesel fuel containing alkyl mono-esters of fatty acids. It has remained the focus of extensive amount of recent research since it is renewable and reduces the emission of some pollutants. The present work emphasis on reduction of diesel engine emission using jatropha based bio-diesel and Di-ethyl ether (DEE). The experiments show that, with 20% (B20) addition of bio-diesel, the BSFC and BSEC increase by 7% and 10% while efficiency and emissions - CO, CO2, NOx, and HC - decreases by 1, 64, 5, 18 and 48% respectively. However, it also shows that, even optimized blend (B20) does not able to meet stringent emission norms _particularly for NOx set by EURO IV. For the further reduction of the NOx, DEE is added from 0% to 5% in B20. The results show that by addition of 4% DEE, the engine performance does not influenced much, however reduction in NOx found to be 40% compared with diesel fuel. A hypothesis is proposed that, _The reduction in engine emission is due to improvement in combustion in presence of DEE_. The hypothesis is validated through combustion analysis showing increase in peak pressure (Pmax) by 7% and reduction in delay period by 1.5 degree with addition of 4% DEE in B20. In the further study optimization of the engine parameters i.e compression ratio, injection pressure and injection timing is adopted to express the output parameter (response - Break Thermal Efficiency) as a function of engine parameters. A standard response surface method (RSM) for this objective. RSM also quantized the relationship between the engine parameters and corresponding response. RSM designs give us an idea of the shape of response surfaces. Box _ Behnken based RSM is having three factors and three levels: further number of experiments conducted for this is much lesser compared to any other technique. In this study, the proposed Box-Behnken design required only 15 runs of experiments for the response surface. Using 'Design Expert' software, 2D and 3D plots are generated. Such plots give an idea of domination of process variables and exhibit the trend of interaction between the variables. Statistical significant test (ANOVA) is carried out to develop a Regression model and its accuracy is verified to predict the output values at nearly all conditions. The response measured through experiments is quite similar to the predicated values obtained using the model. Though, some of the significant issues like: compatibility of bio-diesel with the crankcase lubricating oil, thermal stability of lubricating oil with bio-diesel, changes in physical and chemical properties of lubricating oil with bio-diesel etc. have not been adequately inspected. These requirements are to be addressed in order to conform the long term suitability of bio-diesel in a current family of diesel engines. In the extended work, these problems are addressed. With an overall objective of life cycle analysis, a long run endurance test (512 hours) is carried out on CI engines fueled with diesel and optimized blend of bio-diesel fuel (B20A4) respectively. The endurance tests are directed as per ISO 10000 part IX for the examination of wear of engine components, lubricant's properties, suspended impurities, and wear metal debris. The wear of various component of the engine is characterized by dimension, weight and surface roughness measurements. Lube oil analysis (Atomic Absorption Spectroscopy _ AAS, Ferrography) are performed on oil sample taken after every 128 hours. The wear and lubricating oil analysis suggested that the wear of B20A4 fueled engine is substantially lower compared to diesel. A regression model is also proposed to predict overall wear of the CI engine.