Numerical study of ignition process of ternary hydrogenated catalytic biodiesel/methanol/n-octanol blends under high-temperature and high-pressure conditions

Abstract

This article presents a numerical simulation study of the spray combustion process of methanol/n-octanol/hydrogenated catalytic biodiesel (HCB) blended fuel in a high-temperature and high-pressure constant volume combustion chamber environment, using the Reynolds-averaged Navier-Stokes (RANS) method. This study focuses on the effects of the fuel properties on two-stage ignition processes. The blended fuel, denoted as M15, is composed of methanol, octanol, and HCB in volume ratios of 15 %:17 %:68 %. The pure HCB (M0) was also calculated under the same operating condition as references. The results indicate that M15 exhibits significant delays in both high-temperature and low-temperature ignition compared to M0. At low ambient temperatures, methanol demonstrates a strong inhibitory effect on spray ignition in part due to its competition with alkanes for OH radicals. Additionally, high-temperature ignition of M0 primarily occurs at the periphery of the spray, whereas the ignition of M15 transitions toward the fuel-rich region near the nozzle exit. This transition is attributed to the ignition delay, which provides better-mixing characteristics in the M15 spray, along with the oxygen content introduced by methanol.