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A new type of fuel injection nozzle, called a “slit nozzle,” has been developed to improve poor ignitability and to stabilize combustion under low load conditions in direct-injection methanol diesel engines manufactured for medium-duty trucks. This nozzle has a single oblong vent like a slit. Engine test results indicate that the slit nozzle can improve combustion and thermal efficiency, especially at low loads and no load. This can be explained by the fact that the slit nozzle forms a more highly concentrated methanol spray around the glow-plug than do multi-hole nozzles. As a result, this nozzle improves flame propagation.

A numerical model has been developed to predict the formation of NOx and formaldehyde in the combustion and post-combustion zones of a methanol DI engine. For this purpose, a methanol-air mixture model combined with a full kinetics model has been introduced, taking into account 39 species with their 157 related elementary reactions. Through these kinetic simulations, a concept is proposed for optimizing methanol combustion and reducing exhaust emissions.

An experimental and numerical study has been conducted on the emission and reduction of HCHO (formaldehyde) and other pollutants formed in the cylinder of a direct-injection diesel engine fueled by methanol. Engine tests were performed under a variety of intake conditions including throttling, heating, and EGR (exhaust gas recirculation) for the purpose of improving these emissions by changing gas compositions and combustion temperatures in the cylinder. Moreover, a detailed kinetics model was developed and applied to methanol combustion to investigate HCHO formation and the reduction mechanism influenced by associated elementary reactions and in-cylinder mixing.