THE TEMPERATURE DEPENDENCE OF LAMINAR BURNING VELOCITIES OF METHANOL-SYNGAS-AIR FLAMES

摘要

Using the simplest alcohol - methanol - as a fuel for spark ignition (SI) engines, enables an increase of thermal efficiency compared to gasoline. Additionally, with the enrichment of hydrogen rich gas from methanol reforming (syngas) using exhaust heat, the efficiency can be further improved. The complexity of optimizing such an arrangement asks for numerical support. However, there is no research that publishes the effect of unburned mixture temperature and equivalence ratio on the laminar burning velocity of methanol-syngas blends, which is needed for developing an engine cycle code to simulate methanol fueled SI engines with syngas addition from exhaust gas fuel reforming. The influence of temperature on the laminar burning velocity of methanol-syngas blends is investigated in this study using CHEM1D. The simulation shows that the flame speed increases dramatically with the enrichment of syngas, especially at lean and rich conditions. The effect of syngas ratio on the improvement of burning velocity is less important at higher temperatures, and there is almost no influence at stoichiometry. Some well-known mixing rules are then examined. In general, the Hirasawa mixing rule shows the best fit with the numerical data. For blends with high syngas content, the Le Chatelier's mixing rule is recommended. The temperature power exponent α is calculated and compared to other correlations. It shows that the published correlations are unable to predict the influence of temperature on laminar burning velocity accurately enough for the combustion of methanol, syngas and their blends in air.