Performance and Emission Characteristics of a Diesel Engine Fueled by Biodiesel-Ethanol-Diesel Fuel Blends

There is growing interest to study the effect of blending various oxygenated additives with diesel or biodiesel fuel on engine performance and emission characteristics. This study aims to analyze the performance and exhaust emission of a four-stroke, four-cylinder diesel engine fueled with biodiesel-ethanol-diesel. Biodiesel was first produced from crude Jatropha oil, and then it was blended with ethanol and fossil diesel in different blend ratios (B10E10D80, B12.5E12.5D75, B15E15D70, B20E20D60 and B25E25D50). The engine performance and emission characteristics were studied at engine speeds ranging from 1200 to 2000 rpm. The results show that the brake specific fuel consumption increases while the brake power decreases as the percentage of biodiesel and ethanol increases in the blend. The exhaust emission analysis shows a reduction in CO2 emission and increase in NOx emission when the biodiesel -to- ethanol ratio increases in the blends, when compared with diesel as a reference fuel.

Performance Analysis of a Combined Cycle Power Plant with Simultaneous Cooling of Inlet Air Streams to the Compressor and Condenser

This paper presents the thermodynamic performance analysis of an existing combined cycle power plant to be retrofitted with a waste heat driven aqua lithium bromide absorption refrigerator for cooling the inlet air streams to the compressor and air-cooled steam condenser. The power plant is located in the hot and humid tropical region of Nigeria, latitude 4°45′N and longitude 7°00′E. This was achieved by performing energy and exergy analysis of the integrated system. Using the operating data of the existing combined cycle power plant, the results of the analysis showed that by cooling the inlet air streams to 15oC at the compressors, and to 29oC at the air-cooled steam condenser, the net power output, thermal and exergy efficiencies of the combined cycle plant increased by 7.7%, 8.1% and 7.5% respectively while the plant total exergy destruction rate and specific fuel consumption dropped by 10.8% and 7.0% respectively. The stack flue gas exit temperature reduced from 126oC to 84oC in the absorption refrigerator, thus reducing the environmental thermal pollution. The COP and exergy efficiency of the refrigeration cycle was 0.60 and 27.0%, respectively. Results also show that the highest rate of exergy destruction in the combined cycle power plant occurred in the combustion chamber while the highest rate of exergy destruction in the absorption refrigeration cycle occurred in the evaporator followed by the absorber.