The search for alternative fuels for internal combustion engines is ongoing. Among the alternatives, plant-based fuels can also be mentioned. Alcohol is not a common fuel for diesel engines because the physical and chemical properties of the alcohols are closer to those of gasoline. In our research, the combustion properties of diesel-n-butanol mixtures have been investigated to obtain results on the effect of butanol blending on combustion. Among the combustion properties, ignition delay, in-cylinder pressure, and heat release rate can be mentioned. They have been observed under different compression conditions on an engine on which the compression ratio can be adjusted. The method used was a quite simple one, so the speed of the engine was set to a constant 900 rpm without load, while three compression ratios (19.92, 15.27, and 12.53) were adjusted with a fuel flow rate of 13 mL/min and the pre-injection angle of 18^◦ BTDC. Blending butanol into the investigated fuel does not significantly affect maximal values of indicated pressure, while much more effect on the pressure rising rate can be detected. Furthermore, heat release rate and ignition delay increased at every compression ratio investigated. Despite the low blending rates of butanol in the mixtures, butanol significantly affects the combustion parameters, especially at high compression ratios.

The ambient air around us is continuously and increasingly loaded and polluted through emission that comes from different sectors, especially from the transportation sector. This fact is due to the growing energy consumption in the transport sector which is forecasted worldwide in the nearer and far future. Bio-based energy may be consumed in an increasing way in the sector until 2050. Methanol, and if it is produced on bio-basis, called bio-methanol, is the simplest alcohol. Methanol costs less than other automotive alternative alcohols, for example, ethanol or butanol, so it may be among the cheapest technical alcohols. As for methanol’s structure, it contains 30% more inherent oxygen on a molecular base than fossil diesel. The aim of this research is to give comprehensive overview about the methanol’s effect on the combustion and emission properties of a diesel engine. During the analyses of combustion and emission characteristics the most relevant parameters have been included. The study also contains calculations regarding theoretical combustion (oxidation process) of the different hydrogen-carbons. A rarely investigated parameter, O2 consumption or demand is also in focus, besides CO2 emission and intensity throughout the calculations. For our experimental test series, diesel fuel was the base fuel and it has been mixed with biodiesel first, and this mixture has been further blended with methanol. Methanol’s theoretical contribution to the diesel–biodiesel blend’s O2 consumption and CO2 emission is a small amount. Engine’s external parameters have not changed significantly if it is running on blend with methanol. Methanol has rather affected the combustion and emission properties of the engine more significantly.