Effect of Multiple Injections on Particulate Size-Number Distributions in a Common Rail Direct Injection Engine Fueled with Karanja Biodiesel Blends

Use of alternative fuels, and reduction of particulate and NOx emissions are major challenges for making diesel engines environmentally benign. Measures adopted for reducing gravimetric particulate emissions necessarily always do not reduce particulate number concentration, which is strongly related with adverse health effects. Current emission norms in some parts of the world limit particulate number concentration along with particulate mass. In this scenario, it becomes important to investigate effect of fuel injection parameters and fuel injection strategies such as pilot injections on particulate size-number distribution. A single cylinder research engine is used to evaluate the effect of different fuel injection strategies and injection timings (for pilot and main injections) on particulate size-number distribution and total particulate numbers. Experiments were conducted at two fuel injection pressures (500 and 1000 bar) for different injection timings for biofuels (20% and 50% Karanja biodiesel blends) and the results are compared with baseline data of mineral diesel. Particulate number-size distribution decreases with increasing fuel injection pressure. For a fixed pilot injection timing, particulate number-size distribution increases with retarded main injection for all test fuels. Total particulate number concentration of biodiesel blends is lower than mineral diesel. Utilization of 20% blend of Karanja biodiesel results in highest reduction of particulate number emissions at retarded start of injection timing.