Combustion and emission characteristics of wood pyrolysis oil-butanol blended fuels in a DI diesel engine

We investigate the emission and combustion characteristics of a biomass-based fuel that is primarily comprised of two biofuels, namely, wood pyrolysis oil (WPO) and n-butanol in a DI diesel engine. WPO has been of interest as an alternative fuel to conventional fossil fuels in several countries. The use of WPO in conventional internal combustion engines, however, requires modifications of their fuel supply systems due to its poor fuel properties of high viscosity, high water content, and low cetane number. In addition, since WPO is chemically unstable, gummy polymers are spontaneously generated, increasing the viscosity of the fuel. In the present study, it is shown that n-butanol plays an important role in facilitating the use of WPO in an internal combustion engine. Principally, n-butanol can be mixed with WPO without any phase separation. Additionally, n-butanol has a viscosity of 3.1 cSt that is similar to the viscosity value of 2.7 cSt for diesel, and can effectively lower the viscosity of the blended fuel. As an organic solvent, n-butanol is capable of dissolving solid particles existing in WPO and suppressing polymerization. In order to achieve a stable combustion of WPO-butanol blended fuels, we introduce a high compression ratio diesel engine. Experimental results show that the combustion of WPO-butanol blended fuels yields lower particulate matter emissions than diesel fuel combustion.