The use of fossil fuels further developed and give a convenient human civilization. However, the use of fossil fuels increases the risk of environmental pollution and resource depletion. In particular, internal combustion engines in the transportation sector, which use fossil fuels as an energy source, account for a large portion of the world''s total energy use. Many researchers are trying to improve the fuel efficiency of and reduce environmental pollutants by increasing the efficiency of internal combustion engines. In addition, the research on fuel, the source of power for internal combustion engines, as well as mechanical improvement and development of engines, is also being actively carried out. By using biomass, which is a representative example of new energy sources for internal combustion engines, biodiesel and bioethanol are produced and applied to internal combustion engines to replace parts of fossil fuels with improvements in exhaust pollutants. Biodiesel and bioethanol are capable of producing fuel using vegetable or animal oils. Biodiesel and bioethanol contain oxygen, which can improve combustion efficiency, reducing emissions of exhaust pollutants.
In this experiment, biodiesel palm oil biodiesel and bioethanol were blended with diesel fuel and applied to Common Rail Direct Injection Diesel Engine. In particular, the engine condition was at low idle speed. This is the condition in which the engine has the lowest rotational speed, the flow in the combustion chamber is slow and the atomization of the fuel injected into the combustion chamber by the low injection pressure is relatively poor. The high viscosity characteristic of biodiesel leads to poor atomization. This affects more severely the combustion characteristics and the generation of exhaust pollutants in low idle conditions. And although bioethanol has a low viscosity that can improve the atomization, its cooling effect by the high latent heat of evaporation affects the combustion in the cylinder significantly in this low idle condition.
The application of biodiesel to low idle conditions increased the maximum combustion pressure and heat release rate. And nitrogen oxides could be reduced by up to 5.9% depending on engine load, and the emission level and particle size of the soot decreased due to the influence of the oxygen content of biodiesel. And the benzene, toluene, ethylbenzene, and xylene which are involved in toxic aromatic volatile organic compounds were detected. Benzene increased depending on engine load conditions. However, the application of pure biodiesel at low idle conditions under high loads reduced benzene.
The application of bioethanol in low idle conditions enabled the simultaneous reduction of NOx and Soot opacity. The cooling effect of bioethanol due to the high latent heat of evaporation increased ignition retardation, but it suppressed the production of NOx. The high oxygen content of bioethanol reduced the emission of soot. However, HC and CO tended to increase.