Influence of Glycerol on Methanol Fuel Characteristics and Engine Combustion Performance

Abstract

Methanol derived from solar energy is a carbon-neutral alternative fuel for engines. The low viscosity of methanol is one of the problems that restrict its direct compression ignition application in engines. Glycerol is a renewable resource derived from biomass, and its viscosity is more than 1700 times that of methanol. In this study, glycerol was mixed with methanol in different volume fractions (1–50%), and a methanol-glycerol mixture with similar viscosity to diesel was prepared. Then, the particle size, electrical conductivity, viscosity, swelling and corrosion characteristics of the mixed fuel were measured. Finally, the combustion and emission tests of methanol-glycerol mixed fuel were carried out on a heavy-duty multi-cylinder diesel engine. The results show that glycerol can effectively adjust the viscosity of the mixed fuel. The viscosity of the mixed fuel can reach 3.19 mm2/s at 20 °C when blended with 30% glycerol by volume, which meets the requirements of the national standard for diesel fuel. The addition of glycerol can alleviate the corrosion of methanol to the polymer. The test of the mixed fuel in the direct compression ignition engine shows that the thermal efficiency of methanol mixed with 5% glycerol was further improved than that of pure methanol, both of which were significantly higher than the thermal efficiency of diesel compression ignition engines. Methanol and 5% glycerol by volume blends can reduce soot and nitrogen oxide emissions while maintaining low HC and CO emissions. Therefore, proper blending of glycerol in methanol fuel can optimize the fuel properties of methanol and achieve higher thermal efficiency and lower pollutant emissions than pure methanol direct compression ignition.