The improvements of a diesel engine fueled with renewable and sustainable diesel/n-butanol/polyoxymethylene dimethyl ethers blended fuels at high altitudes

Atmospheric conditions at high altitudes deteriorate combustion in the cylinder of compression ignition (CI) engines, severely degrading engine performance and increasing soot emissions. The use of oxygenated fuels as an alternative fuel to diesel is an effective solution to improve performance and reduce emissions of highland CI engines. Before optimizing a highland CI engine, it is necessary to determine the law of influence of oxygenated fuels on the performance and emission characteristics of the engines. This paper focuses on the effect of diesel/n-butanol/polyformaldehyde dimethyl ether blends on the combustion, performance, and emission characteristics of a CI engine at different simulated altitudes (0 m, 2000 m, 3000 m, and 4000 m). First, a three-dimensional computational fluid dynamics (3D-CFD) simulation model was developed and validated by experimental results. Second, the 3D-CFD model coupled with a chemical kinetic mechanism including 164 species and 643 reactions was used to simulate the combustion process in the cylinder under different operating conditions. The results showed that the high-altitude environment increased the cylinder temperature, peak heat release rate, ignition delay, soot emissions, HC emissions, and brake specific fuel consumption, and reduced BTE, and NOx emissions of the CI engine compared with the plains. At the same altitude, the use of n-butanol and PODE3 provided oxygen for in-cylinder combustion, which somewhat promoted more complete combustion in the cylinder, reduced HC and soot emissions and increased BTE. Although the use of oxygenated fuels in highland CI engines elevated NOx emissions, the problem could be solved by methods such as LTC and SCR. Overall, n-butanol and PODE3 are promising alternative fuels for highland CI engines, mitigating to some extent the problems of higher soot and HC emissions and lower BTE associated with high-altitude environments.