EXPERIMENTAL ANALYSIS OF BIOGAS RUN DUAL-FUELLED DIESEL ENGINE PERFORMANCE

Abstract

The price of fossil fuels is constantly increasing because of the limitations of deposit, supply and increase in demand for petroleum fuels resulting from industrialization. The regulations for emissions from diesel engines have also been strengthened, especially for particulate matter (PM) and oxides of nitrogen (NOx). There is therefore need to find alternative fuels which will reduce harmful exhaust emissions while maintaining high thermal efficiency. Biogas is one such fuel, which can be adapted for use in internal combustion (IC) engines. In this research, a Direct Injection Compression Ignition (DICI) engine was modified into a dual fuel engine which uses biogas and pilot fuel, with the focus on reduction of harmful exhaust emissions while maintaining high thermal efficiency. Diesel,biodiesel,alcohol were used as the pilot fuel wherease biogas was considered as the gaseous fuel. The performance and emission characteristics of the modified engine were compared with those of the conventional diesel engine. The air intake system of the engine was modified to allow mixing of air and biogas before supplying the mixture to the combustion chamber of the engine. The results obtained from this study showed that a DICI engine can be modified into a dual fuel engine that uses diesel and biogas. Engine performance tests were done for single fuel mode and dual fuel modes. Exhaust emissions of HC, CO, NOx and CO2 were measured for the various operating conditions. The results showed that at maximum substitution of pilot fuel with biogas (Biogas:SBDO in the ratio 80:20) occur in the case where SBDO is considered as pilot fuel. The brake thermal efficiency however, decreased from 33.23% in diesel mode to 18.86% in diesel dual fuel mode due to the lower calorific value of biogas compared to diesel. The performance characteristics of the modified engine showed that diesel can be substituted partly with biogas and the engine used for a range of applications. The most appropriate areas of use are stationary applications such as driving of electric power generators, hoisting in construction sites and driving of machines such as water pumps and concrete mixers. This is due to the challenge of compact storage of the gas.