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The present study extends our previous methane flame chemistry to methane autoignition based on most recent shock-tube experiments. It results in a detailed mechanism that consists of 128 elementary reactions among 31 species and that can be applied to predicting methane autoinginition times for temperatures between 1000 K and 2000 K, pressures between 1 bar and 250 bar and equivalence ratios between 0.4 and 3. A 9-step short mechanism is derived from this detailed mechanism with the objective of predicting knock in dual-fuel engines for equivalence ratio between 0.5 and 1.5 with temperature ranging 800 to 1200 K and pressure from 50 to 150 bar.

Turbulent combustion in cylinders can be considered to involve chemistry of two different types, namely fast and slow in comparison with the turbulence. Different methods are needed for addressing these two types of chemistry. Turbulent mixing controls the fast chemistry, which proceeds as rapidly as advancing turbulent fronts allow. Slow chemistry is more oblivious to turbulence and proceeds at rates dependent on local temperature, pressure and chemical composition. Reaction-sheet descriptions thus may be applied to fast chemistry and distributed-reaction descriptions to slow. This work addresses methods for describing combustion processes that treat fast and slow chemistry differently. In premixed charges, the principal heat-release rates are fast. Turbulence modeling is suggested to be sufficient for describing the propagation of the main heat-release fronts. Slow chemistry includes autoignition, CO burnup and NOx production.