부산대학교 도서관

As the consumption of fossil fuel has deepened andenvironment pollution has intensified, the demands on new renewable green energy are growing more and more intensely. Oil, coal, natural gas and other fossil fuels are the main energy of modern production and contemporary life. But, the faster the fossil fuels are used, the fewer time is life for human beings to us them. Biodiesel, as a clean energy source which can reduce environmental pollution compared to fossil fuel, is becoming increasingly important. The biodiesel can be produce from various vegetable oils, waste cooking oils, and animal fats, and its fuel properties change with the different feed stocks. It is well-known that diesel engines can run on biodiesel blended with conventional diesel without modification. However, through investigating the use of pure vegetable oils in diesel engines, researchers found that they cause numerous engine-related problems. Therefore, vegetable oils must be blended with pure diesel because the net calorific value of biodiesel is less than that of conventional diesel fuel, its viscosity, density, and iodine values are higher, and its volatility is poor. Those shortcomings lead to severe engine deposits, injector coking, and piston ring sticking if vegetable oils are used on their own. Their high density, viscosity, and surface tension decrease the quality of atomization and combustion performance. After transesterification, however, biodiesel can acquire properties closer to those of diesel. Many researchers found that the best volume mix of biodiesel and diesel is 20 to 80. Its combustion performance is closest to diesel fuel and better than diesel in terms of emission reduction. In this study, we investigated the effects of canola oil biodiesel (BD) to improve combustion and exhaust emissions in a common rail direct injection (DI) diesel engine using BD fuel blended with diesel. Experiments were conducted with BD blend amount of 20% on a volume basis (BD20) under a constant engine speed of 1500rpm. And the main injection timing was fixed at the top dead center (TDC) 0 degree, the combustion performance and emission characteristics were investigated according to various pilot injection timings and engine loads. The experimental results showed that with the increasing engine load, the combustion pressure, brake specific fuel consumption (BSFC), brake specific energy consumption (BSEC), and peak combustion pressure (Pmax) were increased. In case of exhaust emissions, the Nitrogen Oxides (NOx) and Particulate matters (PM) emissions were also increased slighty, but the Carbon Oxides (COx) emission was obviously reduced. On the other hand, as the injection timing advanced, the combustion pressure, BSFC, BSEC, heat release rate (HRR), and Pmax were changed slightly, the CO emission was obviously reduced, NOx and PM emission were increased a little. The ignition delay was increased by about 3~8 crank degree.