In recent years, fuels that lower CO2 emissions have been developed to achieve carbon neutrality. In Europe, a new emission regulation called Euro 7 is planned to be introduced for passenger vehicles from 2028. Notably, methanol is a promising fuel because it can be synthesized relatively easily and converted into various chemical products. Moreover, it is liquid at room temperature and pressure, making it superior for transportation and storage. However, methanol has a low cetane number; thus, it is necessary to co-burn with a readily auto-ignited fuel such as diesel fuels. Although the dual fuel combustion of diesel-methanol has an inhibitor effect that prolongs the ignition delay, few studies have been reported. Therefore, this work aims to investigate how methanol energy ratio and excess air ratio affect combustion characteristics. The experiment utilized a Rapid Compression and Expansion Machine (RCEM) with a compression ratio of 13.8. Results were analyzed using pressure diagrams, rate of heat release, and visualized images of the combustion process taken by a high-speed camera at 10,000 fps. It was yielded under the engine speed equivalent to 850rpm, the methanol energy ratio increase, and excess air ratio decrease resulted in prolonging the ignition delay time. Additionally, sensitivity analysis and rate of production analysis of the diesel-methanol dual fuel combustion process were performed using a detailed chemistry model to examine the mechanism of inhibitor effect.
MORIWAKI et al. (Wed,) studied this question.