In the thesis the effect of diesel-methanol blends on combustion and emission characteristics is studied. The main objective of methanol addition is to lower exhaust emissions, while keeping other engine parameters within acceptable ranges (eg. power, effective efficiency and fuel consumption). Methanol features high oxygen concentration, low sulfur concentration, low density and high latent heat of vaporization, while it can be produced from renewable sources with various technologies. Based on simulations carried out in AVL Fire the effect of 10%, 20% and 30% methanol-diesel blends was evaluated. Furthermore the influence of injection timing (690˚, 707˚ and 715˚) and the effect of EGR (0%, 30% and 70%) were also studied. The results show that with an increase in methanol fraction the ignition delay became longer, which caused higher heat release rate in premixed phase of combustion and consequently shorter burn duration. Due to late combustion after top dead center, temperature and pressure in the cylinder decreased with increasing methanol fraction. Consequently NOx emissions were lower while soot emissions were higher than those for neat diesel. Advanced injection timing (690˚) caused an increase in pressure and temperature while ignition delays were also longer for all fuels. Meanwhile retarded injection exhibited diametrical results. Emissions of NOx increased with advanced and decreased with retarded injection. The use of EGR provoked an increase in ignition delay time, while also lowering pressure and temperature in the cylinder. Consequently NOx emissions decreased. Detailed analysis of radical formation revealed that OH radical mostly formed in the area where combustion rate reached it's peak.
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