Study on spray and combustion characteristics of Fischer-Tropsch diesel/biodiesel blends in a constant volume chamber

Abstract

Fischer-Tropsch (F-T) diesel synthesized from coal is a promising alternate fuel for diesel engines. Because F-T diesel has low viscosity and does not contain oxygen, biodiesel is added to F-T diesel in this study to increase the viscosity and oxygen content of F-T diesel. In this study, the effects of adding different proportions of biodiesel (20% and 50% in volume) to F-T diesel on spray and combustion characteristics are investigated using constant volume chamber (CVC). The experimental results show that among petro-diesel, F-T diesel, and biodiesel, F-T diesel has the best evaporation performance and biodiesel has the worst. When biodiesel is added to F-T diesel, the evaporative property of the fuel becomes worse. At the ambient temperature of 773K, the liquid spray projected area of FB20 and FB50 increase by 28.9% and 64.9%, respectively, compared with FT100. Compared with petro-diesel, F-T diesel and biodiesel have shorter ignition delay and flame lift-off length. In addition, the flame temperature and KL of biodiesel are significantly lower. After blending biodiesel with F-T diesel, the ignition delay and flame lift-off length gradually increase, which will be beneficial for air fuel mixing. In addition, adding biodiesel will lower the flame temperature and KL. Compared with F100, the KL of FB20 and FB50 decrease by 7.4% and 20.2%, respectively.