An Experimental Study on the Spray, Combustion, and Emission Characteristics of Two Types of Biodiesel Fuel

Abstract

In this study, we produced pure biodiesel and analyzed its properties. Also, pure biodiesel was blended with conventional diesel fuel in volumetric mixing rates of 5%, 20%, and 35%. Therefore, a total seven kinds of fuels were tested for this study. Injection quantity was measured according to the blending rate. Spray penetration, distribution, and evaporation characteristics were also clarified through a spray visualization system. Furthermore, the combustion flame was investigated using a single cylinder optical engine and a high-speed camera to understand how evaporation characteristics affect the combustion flame. Moreover, exhaust emissions were measured with an exhaust emission analyzer and a smoke meter. According to the results of the injection test, there were few differences between the characteristics of diesel and biodiesel-blended fuel regarding the injection quantity and penetration length when the fuel temperature was maintained at 60 degrees C. Hence, there were not any problems such as additional correction of the injection duration and pressure found to be used for the engine tests as long as the fuel temperature was properly controlled. From the spray RMS images, two types of biodiesel-blended fuels showed nonuniform spray distributions compared to diesel, indicating that biodiesel-blended fuel had worse evaporation characteristics. The flame visualization experiment showed that the combustion flame characteristics of diesel and biodiesel-blended fuels were similar; however, white smoke was observed at the start of ignition with the biodiesel-blended fuel due to its poor atomization characteristics. From the emission results, the biodiesel-blended fuels showed higher levels of NOx emissions compared to diesel, and it could be expected that the oxygen content and rapid combustion of the biodiesel-blended fuel amplified NOx generation. Also, as a result of combustion image analysis through an image processing, the PM distribution rates of biodiesel-blended fuels were significantly lower than that of diesel, and it showed a similar trend to the exhaust emission data. Therefore, it was judged to be a useful and valid method for analyzing the relationship between combustion and emission.