Combustion and emissions of an automotive diesel engine using biodiesel fuels under steady and start conditions

摘要

Biodiesels have been proved to reduce the smoke and THC emissions by many researchers. The demands of biodiesel are increasing all over the world. Various feedstocks of biodiesel have been used in different countries and regions. The blend ratio of biodiesel in petrol station is also varies. Therefore, more calibration works have been done for the car manufacturers. In first part this research, the combustion characteristics and emissions of using biodiesels from different feedstocks with different blend ratio was studied by experimental works. Statistical analysis indicated the correlation between emissions and fuel properties. Then, a smoke index, containing Reynolds Number of fuel spray, cetane number and gross heat value of combustion, was created and showed a significant linear relationship with the smoke emissions. The effects of engine loads and EGR rates on the relationship were also discussed. The second part of this research was focused on the cold start with using biodiesel blends. The tests were conducted in a wide range of the temperatures (from -20°C to 90°C). Results showed that the methyl ester biodiesel reduced the PM during the acceleration period of the start at 20°C conditions. As ambient temperature decreased, using of biodiesel shows an increased emissions of PM and THC. The chemical compositions of particle emissions with using biodiesel blends at cold start were identified by a 20-GC/MS and the results also confirmed this trend.