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A software “Automatic Scheme Reduction Tool (ASRT)” [1], which was developed by the authors to reduce the number of detailed elementary reactions automatically with CHEMKIN-II code [2], was applied to the reduction of the elementary reaction scheme for gas oil, ethanol and dimethyl ether (DME). It was found that the reduced scheme obtained for a fuel-rich mixture has the capability to predict heat release histories and ignition delay characteristics not only for fuel-rich mixtures, but also for stoichiometric and lean mixtures. As a result, the reduction scheme for DME, which was obtained by the ASRT combined with optimization method, was applied to three-dimensional engine combustion analysis.

In order to numerically simulate the mixture formation and combustion processes in a direct-injection gasoline engine, the validity of the submodels for fuel spray and combustion was investigated. The physical model proposed by the authors was employed for hollow-cone sprays injected from a swirl injector along with the authors' original submodels. This hollow-cone spray model was validated by comparing the calculated and measured results of the behavior of hollow-cone free spray. As a combustion model, Reitz's model was employed. These submodels were incorporated into the authors' GTT code, and the mixture formation and combustion processes in a direct-injection gasoline engine were numerically analyzed using this code. The validity of the submodels was confirmed by comparing the calculated results of the temporal variation of fuel vapor concentration and gas pressure in the cylinder with the experimental ones under various operating conditions of stratified charge combustion.