Performance study of diesel/hydrogen-rich gas engine based on methanol decomposing and waste heat recovery

Dissociated methanol gas (DMG) is a hydrogen-rich mixture produced from methanol using engine exhaust heat. In this study, a diesel/DMG dual-fuel engine was developed to investigate the effects of DMG blending on performance under typical operating conditions and to explore the potential of exhaust-heat-driven methanol decomposition for improving efficiency and reducing fuel cost. DMG generated in a methanol decomposition reactor was introduced into the cylinder to co-combust with diesel. Results show that at a 20 % substitution ratio, the engine's thermal efficiency increased by (1.08 ± 0.08)% and fuel costs decreased by (10.47 ± 0.25)%. The improvement was statistically significant ( p < 0.05). DMG addition led to higher peak cylinder pressure, pressure rise rate, and heat release rate, along with advanced combustion phasing, a shorter combustion duration, and slightly increased cycle-to-cycle variation. Regarding emissions, NOx increased with higher substitution ratios, while soot exhibited a slight rise. HC emissions first decreased and then increased marginally, whereas CO emissions showed a small increase. Blending DMG with diesel not only recycles exhaust heat but also modifies combustion characteristics, improving engine efficiency and lowering operational costs. This method presents a competitive and promising pathway for the efficient utilization of future clean energy. • Methanol online dissociation could recycle engine exhaust heat. • Prototype of the diesel/dissociated methanol gas engine was built and studied. • Blending dissociated methanol gas could improve the overall efficiency of the engine. • The engine heat release rate was improved and the combustion duration is shortened.