Characteristics of particulate emissions of compression ignition engine fueled with biodiesel derived from soybean

An experimental investigation was performed on the effect of engine speed, exhaust gas recirculation (EGR), and boosting intake pressure on the particulate size distribution and exhaust gas emissions in a compression ignition engine fueled with biodiesel derived from soybean. The results obtained by biodiesel fuel were compared to those obtained by petroleum diesel fuel with a sulfur content of 16.3 ppm. A scanning mobility particulate sizer was used for size distribution analysis, and it measured mobility equivalent particulate diameter in the range of 10.4 - 392.4 nm. In addition to the size distribution of the particulates, exhaust emissions, such as oxides of nitrogen (NOx), hydrocarbon, and carbon monoxide emissions, and combustion characteristics under different engine operating parameters were investigated. The engine operating parameters in terms of engine speed, EGR, and intake pressure were varied to investigate their individual impacts on the combustion and exhaust emission characteristics. As the engine speed was increased for both fuels, the larger size particulates, which dominantly contribute particulate mass, were increased; however, total numbers of particulate were reduced. Compared to diesel fuel, the combustion of biodiesel fuel reduced particulate concentration of relatively larger size where most of the particulate mass is found. Moreover, dramatically lower hydrocarbon and carbon monoxide emissions were found in the biodiesel-fueled engine. However, the NOx emission of the biodiesel-fueled diesel engine shows slightly higher concentration compared to diesel fuel at the same injection timing. EGR significantly increased the larger size particulates, which have diameter near the maximum measurable range of the instrument; however, the total number of particulates was found not to significantly increase with increasing EGR rate for both fuels. Boosting intake pressure shifted the particulate size distribution to smaller particulate diameter and effective reduction of larger size particulate was found for richer operating conditions.