Experimental investigation of methanol–biodiesel blend at high altitude: kinetic and performance characterization

This study investigates the combustion and emission characteristics of a methanol–biodiesel blend (BM20) under high-altitude conditions. A detailed reaction mechanism for methanol–biodiesel blends was developed for kinetic analysis. The results indicate that methanol addition at temperatures above 1000 K generates substantial quantities of OH radicals, while reducing the molar concentrations of acetylene (C2H2) and ethylene (C2H4)—key precursors of polycyclic aromatic hydrocarbons (PAHs). Experimental data further demonstrate that methanol can significantly mitigate the adverse effects of high-altitude intake hypoxia. Compared with diesel and biodiesel, BM20 shows superior performance. The brake thermal efficiency (BTE) of BM20 increases by up to 2.5 %. At medium–high loads, the power output rises by a maximum of 3.8 %, while the exhaust gas temperature (EGT) decreases by up to 12.4 %. NOx emissions decline by a maximum of 3.6 %, and low exhaust smoke levels are maintained under all load conditions, with peak reductions reaching 83.2 %. Notably, at higher load, both NOx and smoke emissions decrease simultaneously. These findings suggest that the distinctive combustion chemistry of methanol can facilitate cleaner and more efficient engine operation in oxygen-deficient environments.