Global warming and climate change have led to a greater interest in the implementation of biofuels in internal combustion engines. In spark ignited engines, biofuels have been shown to improve efficiency and knock resistance while decreasing emissions of unburned hydrocarbons, carbon monoxide and particles.
This study investigates the effect of biofuels on SI engine combustion through a graphical compilation of previously reported results. Experimental data from 88 articles were used to evaluate the trends of the addition of different biofuels in gasoline. Graphs illustrating engine performance, combustion phasing and emissions are presented in conjunction with data on the physiochemical properties of each biofuel component to understand the observed trends.
Internal combustion engines have the ability to handle a wide variety of fuels resulting in a broad range of biofuel candidates. Three groups of oxygenated liquid biofuels were investigated in this review: alcohols, ethers and furans. While the investigated alcohols showcase properties associated with increased engine efficiencies (such as higher chemical knock resistance, greater charge cooling and faster laminar flame speeds). They also pose the challenge of greater fuel consumption due to lower energy densities than gasoline. Ethers and furans, on the other hand are favored by current engine designs as they exhibit properties (such as the energy density) closer to gasoline alongside increased chemical knock resistance.
The compiled data summarizes the possibilities to improve efficiency and fuel economy for biofuel and binary blends in SI engines. However, the results also, show that some of the trends are more complex than anticipated. The effect of biofuels on combustion speed, regulated emissions and exhaust temperatures are not proven to be as self-evident as reported in previous studies. Results on multiple blends with focus on the effect of blending on properties would help improve the picture of the effect of future fuels on SI combustion.