COMBUSTION STUDY OF DIESEL ENGINE OPERATING ON BIO-DIESEL

Abstract

The development of engine combining good fuel economy with low exhaust emissions has underlined the importance of engine pressure measurements. It has been observed that cylinder pressure varies cycle-by-cycle in a diesel engine, indicating there by, cycle-to-cycle variation in heat release, leading to cycle-to-cycle variations in the over all performance parameters viz: torque, thermal efficiency, soot formation, emission and noise emitted from the engine. In this work the cycle-to-cycle variation in the combustion process of a diesel engine running on bio-diesel has been studied. The investigation is carried out on a small DI air-cooled, single cylinder four stroke, naturally aspirated variable speed, 5kW diesel engine. The engine is coupled to AVL Alpha-20 eddy current dynamometer. The pressure-crank angle record is obtained by AVL GM12D Miniature Pressure Transducer and Angle Encoder 333. Emission analysis is also carried out using MK3 Hartridge smoke meter and'4000 light AVL Di gas analyzer. The pressure crank angle record has been obtained for five hundred combustion cycles. Each cyclic combustion variation has been expressed by three parameters viz. maximum pressure (Pmax), maximum pressure rise rate (dP/dOmax) and average pressure. The cycle-to-cycle variation in the combustion process is expressed by mean, standard deviation and coefficient of variation of each cyclic combustion variation parameters (Pmax, dP/dOmax, average pressure). The experimental analysis is then carried out for various operating parameters such as engine speed and type of fuel. The COV of maximum pressure for B20 was higher than that of Diesel. The COV of average pressure for B80 and Bio-diesel was found to be varying to the minimum amount. The 20% bio-diesel blend (B20) was found to be the optimum concentration for blending with respect to coefficient of variation of maximum pressure, average pressure and pressure rise rate. The results have been presented to explain important effects of cycle-to-cycle variations of combustion in small direct injection diesel engine using biodiesel as fuel.