Currently, it is necessary to secure sustainable energy and stable energy supply in response to the more strengthened regulations on greenhouse gas emissions due to global warming, the finite nature of fossil fuels, and energy security issues. Major developed countries, including Korea, are making great efforts to introduce and apply renewable energy such as solar, wind, water, biofuel, hydrogen fuel cell, and coal gasification to solve these problems. In particular, biofuels among renewable energy resources can be considered as the most promising alternative to petroleum-based fuels in the distribution infrastructure and vehicles of existing transportation fuels, and it is actually in use widely.
Among these biofuels, bio-alcohols such as bioethanol are currently used as additives or alternative fuels for gasoline, but are known to have an adverse effect on existing fuel supply infrastructure and vehicle.
Therefore, this paper suggests the possibility that bioethanol and biobutanol representing as biofuels might replace a gasoline mostly used among road transport fuels without any modification of gasoline vehicles. Herein, bio-alcohols were blended with petroleum-based gasoline at low level and the experiments were conducted to verify the overall performance.
This study was divided into three categories: effect of low level bio-alcohol blended fuel on the material of the engine fuel delivery systems, characteristics on the engine cleanliness during combustion, and performance characteristics such as fuel economy and exhaust gas of vehicles.
At first, the most commonly used rubber materials for automotive fuel systems such as nitrile butadiene rubber and fluorocarbon rubber were selected for the analysis of the effect of blended fuel on the engine’s fuel delivery system material. The results showed that the compatibility of bioethanol was relatively worse than that of biobutanol or ethanol/butanol blended fuels. The corrosiveness to the metal materials did not appear to be corrosive to iron, nickel, tin, and copper, but in the case of aluminum alloy materials, corrosion occurred severely when 5% or more bioethanol was blended. On the other hand, corrosion did not occur in the case of the 5% biobutanol blended.
Secondly, in terms of engine cleanliness, bio-alcohols blended fuels showed improved cleanliness in both intake valve deposit (IVD) and combustion chamber deposit (CCD) compared to sub-octane gasoline. Particularly, the fuel blended with 7:3 ratio of bioethanol and biobutanol improved engine cleanliness by up to 37% of IVD and up to 36% of CCD. The mixture shows the best engine cleanliness.
Lastly, emission and fuel economy characteristics were investigated by using CVS-75 and HWFET modes for vehicles equipped with GDI and PFI engines. Fuels blended with bio-alcohols and MTBE compare to sub-octane gasoline showed the decrease of 5 ~ 32% of CO and that of 14 ~ 40% of particle number. On the other hand, no significant differences showed on NMHC, NOx and fuel economy. In terms of an unregulated emissions, as expected, the higher aldehyde were emitted from two vehicles fueled with bio-alcohols blended fuel, than that of vehicles operated with sub-octane gasoline.
Based on the results of this study, it is conducted that the use of fuels blended with low level bio-alcohols would be possible without vehicle modification. It is estimated that it’s use would contribute to the reduction of greenhouse gases in the transportation sector. However, in the case of bioethanol, it is expected that additional consideration would be needed for corrosion problems of aluminum alloy materials even at low level blending (5%) of existing vehicles.