Optimization of Chemical Kinetic Mechanism for Efficient Computation of Combustion Process in Advanced Internal Combustion Engine Configurations
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For the development and optimization of future fuels and automotive engines, computer modeling and simulation has proved itself as an inseparable, efficient and cost effective tool to experimental studies. The traditional reliance of computer models on simplified global reaction steps to simulate the combustion and engine performance parameters, such as in-cylinder pressure, heat release rate and pollutant formation could reduce credibility of the predictions as the global reaction steps depend on arbitrary adjustment of model parameters. This study has incorporated detailed chemistry by augmenting the combustion model of a three dimensional unsteady compressible turbulent Navier-Stokes solver with liquid spray injection by coupling its fluid mechanics solution with detailed kinetic reactions solved by a commercial chemistry solver. Detailed chemistry has been incorporated by constructing a novel reduced mechanism for spark ignition engines. Mechanism reduction is carried out through sensitivity analysis of a skeletal reaction mechanism for compression and power stroke utilizing computational singular perturbation (CSP) method and using the low temperature reaction pathway analysis. To use detailed chemistry and enhance the chemical kinetics library of the fluid dynamics code, this research is comprised of the development of an interface between fluid dynamics and chemical kinetics codes for study of gasoline mechanism in a premixed spark ignition engine. A well-established surrogate (isooctane) has been selected for this study because gasoline is a complex mixture of various compounds and hydrocarbons. A distinguishing feature of this study is the use of 90% iso-octane and 10% n-heptane as surrogate fuel because this combination best modeled the results. With this novel approach, the reduced mechanism obtained from this study is used to perform a mesh independent study that validated and showed a good agreement of in-cylinder pressure, heat release rate and emissions against the experimental data for a range of equivalence ratio from ɸ = 0.98 to 1.3 for spark ignition engines.