A study on the combustion and emission characteristics of biobutanol blended diesel fuels in a direct injection diesel engine

Abstract

This study was performed to investigate the effect of pilot injection strategy on the combustion and emission characteristics in a 4-cylinder compression-ignition engine fueled with biobutanol blended diesel fuels. Mixing ratios of experimental fuels were blended on a mass ratio basis. The present study is divided into spray experiments (to provide a basis for the analysis of the main experiment findings) and experiments on combustion and exhaust measurement results under different conditions. This includes experiments to determine the spray characteristics of the biobutanol, the injection duration and injection quantity in accordance with the injector conduction period from the engine, the fuel per unit time by applying the Bosch method, the mass and energy to understand the supply characteristic injection rate experiment. The objective was to investigate the effect of biobutanol-diesel blended fuel on the spray behavior and macroscopic spray characteristics. To analyze spray characteristics of test fuels such as spray tip penetration, spray cone angle, and spray area of biobutanol blended fuels, spray development processes were carried out using high speed camera and pressurized spray chamber visualization system. Based on the measured spray images, the spray tip penetration and spray cone angle were investigated at various energizing timings and injection pressures. In addition, this study was performed to investigate the effect of pilot injection strategy on the combustion and emission characteristics in a 4-cylinder compression-ignition engine fueled with biobutanol blended diesel fuels. The test engine has a compression ratio of 17.3 achieved by using the 150kW EC dynamo to control the performance characteristics of the experimental engine. In order to study the effect of combustion and emission characteristics of blended fuels on injection timing, the experiments were performed under various pilot injection timings, from BTDC20˚ to BTDC60˚, and various load conditions, from 30Nm to 60Nm by increasing 15Nm of load. However, the main injection timing is fixed at that condition. In addition, the mixing ratios of experimental fuels are blended on a mass ratio basis. Tests fuels were mixed at 10% biobutanol and 90% conventional diesel fuel (B10), 20% biobutanol and 80% conventional diesel fuel (B20), and 100% conventional diesel fuel (B0). Results showed the density of biobutanol blended diesel fuels were lower than that for conventional diesel fuel and decreased the injection quantity and injection rate. The results of the visualization experiment show that spray tip penetration and spray area are increased with increasing injection pressure. The spray tip penetrations of butanol blended fuels showed slightly higher values than that of the conventional diesel fuel. In addition, the spray cone angles of butanol blended fuels were made wider than that of conventional diesel fuel by increasing amount of the butanol blending ratio, and spray cone angle increased in accordance with the increase of ambient pressure. The experimental results indicated that the ignition delay of B20 was longer than that of conventional diesel fuel, and the fuel consumption of butanol blended diesel fuels was higher than that of conventional diesel fuel in all cases of pilot injection timing. Although Nitrogen Oxide (NOx) and Soot of butanol blended diesel fuels are lower than those of conventional diesel fuel, Carbon monoxide (CO) and Hydrocarbon (HC) are higher than those of conventional diesel fuel.