Abstract
In this research, a Direct Injection Compression Ignition (DICI) engine was modified into a dual-fuel engine that used biogas as the primary fuel and diesel as pilot fuel, with the focus on reduction of harmful exhaust emissions while maintaining high thermal efficiency. The effect of exhaust gas recirculation (EGR) on engine performance and emission characteristics was studied. The EGR system was developed and tested with different EGR percentages, i.e. 0%, 10%, 20% and 30%. The effect of EGR on exhaust gas temperature and performance parameters like brake specific fuel consumption, brake power and brake thermal efficiency was studied. The performance and emission characteristics of the modified engine were compared with those of the conventional diesel engine. The results showed that EGR led to a decrease in specific fuel consumption and an increase in brake thermal efficiency. With increase in percent (%) of EGR, the percentage increase in brake thermal efficiency was up to 10.3% at quarter load and up to 14.5% at full load for single fuel operation while for dual-fuel operation an increase up to 9.5% at quarter load and up to 11.2% at full load was observed. The results also showed that EGR caused a decrease in exhaust gas temperature; hence it’s potential to reduce NOX emission. However, emissions of HC and CO increased slightly with EGR.
Highlights
Regulations for particulate matter (PM) and oxides of nitrogen (NOX) emissions from diesel engines have beenHow to cite this paper: Hawi, M., Kiplimo, R. and Ndiritu, H. (2015) Effect of Exhaust Gas Recirculation on Performance and Emission Characteristics of a Diesel-Piloted Biogas Engine
Brake Specific Fuel Consumption (BSFC) Figure 2 shows the variation of BSFC with engine load for various percentages of exhaust gas recirculation (EGR); by varying the percentage of exhaust gas which is recirculated under 0%, 25%, 50%, 75% and 100% load
It was found that brake specific fuel consumption decreased with increase in EGR and reached a minimum value at about 20% EGR and increased slightly up to 30% EGR from 50% load to full load
Summary
Regulations for particulate matter (PM) and oxides of nitrogen (NOX) emissions from diesel engines have been. With employment of these cases of EGR, the combustion process improved due to enhancement of the oxidation process in lean mixtures In these cases, the presence of very active radicals and a higher intake charge temperature could promote the combustion process and reduced the chemical availability of unburned fuel in the exhaust gases. The presence of very active radicals and a higher intake charge temperature could promote the combustion process and reduced the chemical availability of unburned fuel in the exhaust gases Their results indicated that the dual-fuel engine can obtain maximum work availability, minimum destruction availability and minimum chemical availability of unburned fuel when 2% of thermal or combined cases of EGR was introduced to the dual-fuel engine under part load operating conditions
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