Engine knock is an important phenomenon that needs consideration in the development of gasoline-fueled engines. In our days, this development is supported using numerical simulation tools to further understand and predict in-cylinder processes. In this work, a model tool chain which uses a detailed chemical reaction scheme is proposed to predict the auto-ignition behavior of fuels with different octane ratings and to evaluate the transition from harmless auto-ignitive deflagration to knocking combustion. In our method, the auto-ignition characteristics and the emissions are calculated using a gasoline surrogate reaction scheme containing pathways for oxidation of ethanol, toluene, n-heptane, iso-octane and their mixtures. The combustion is predicted using a combination of the G-equation based flame propagation model utilizing tabulated laminar flame speeds and well-stirred reactors in the burned and unburned zone in three-dimensional Reynolds-averaged Navier-Stokes. Based on the detonation theory by Bradley et al., the character and the severity of the auto-ignition event are evaluated. Using the suggested tool chain, the impact of fuel properties can be efficiently studied, the transition from harmless deflagration to knocking combustion can be illustrated and the severity of the autoignition event can be quantified.

The incineration of municipal solid waste (MSW) is an attractive technology to generate thermal energy and reduce landfill waste volume. To optimize primary measures to ensure low emission formation during combustion, numerical models that account for varying waste streams and their impact on nitrogen oxide (NO x ) formation are needed. In this work, the representation of the fuel by surrogate species is adopted from liquid fuel and biomass combustion and applied to solid waste devolatilization and combustion. A surrogate formulation including biomass components, protein, inorganics, and plastic species is proposed, and a comprehensive description of the heterogeneous and homogeneous reactions is developed. The presented work combines and extends available schemes from the literature for woody and algae biomass, coal, and plastic pyrolysis. The focus is set on the prediction of fuel NO x and its precursors, including cyclic nitrogen-containing hydrocarbons. Additionally, the interaction of NO x with sulfur and chloride species is accounted for, which are typically released during the devolatilization of MSW. The model allows for predicting thermogravimetric analysis measurement of waste fractions and different waste mixtures. The proposed kinetic mechanism well reproduces NO x formation from ammonia and hydrogen cyanide and its reduction under selective non-catalytic reduction conditions. The chemical model is successfully applied to predict the released gas composition along a grate-fired fuel bed using a stochastic reactor network.

In this work, we apply a sequence of concepts for mechanism reduction on one reaction mechanism including novel quality control. We introduce a moment-based accuracy rating method for species profiles. The concept is used for a necessity-based mechanism reduction utilizing 0D reactors. Thereafter a stochastic reactor model for internal combustion engines is applied to control the quality of the reduced reaction mechanism during the expansion phase of the engine. This phase is sensitive on engine out emissions, and is often not considered in mechanism reduction work. The proposed process allows to compile highly reduced reaction schemes for computational fluid dynamics application for internal combustion engine simulations. It is demonstrated that the resulting reduced mechanisms predict combustion and emission formation in engines with accuracies comparable to the original detailed scheme.

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