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A well-known auto-ignition model for gasoline, which was proposed by Halstead et al, is automatically optimized on computers by using a simple artificial brain including genetic algorithm as learning theory and an intuition model. Arbitrary constants inside the mathematical equations of highly-nonlinear chemical reaction processes can be fitted by using the experimental time-evolutions of several components. Thus, ignition delay, the interval from compression start to ignition occurrence, can be accurately calculated for different types of fuel, production regions, and engine test benches. The intuition model clarifies whether the arbitrary constants are optimized or not. The present approach will be important for building up several types of virtual engines, which are based on zero-dimensional thermodynamic models, ensemble-averaged flow simulators, and large eddy simulation (LES).

Large Eddy Simulation of the turbulent premixed-flame in engine is performed in a wide range of the operating conditions such as engine speed, air-fuel ratio, and ignition timing. Firstly, a mathematical formulation suitable for Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) of the compressible turbulence and combusting flows is derived, which is the Multi-Level formulation. And a numerical algorithm based on the formulation is developed in order to calculate precisely the supergrid fluctuations of the physical quantities. As the determinations of the subgrid-turbulence and flame wrinkling, the Yakhot-Orszag turbulence model based on the Renormalization Group theory(RNG theory) and a flame-sheet model are combined with the numerical code. Computations are performed for a real engine with dual intakeport and valves. Obtained computational data agrees well with the experimental data on turbulence-intensity and pressure history.

A theoretical model based on a nonlinear ordinary differential equation was developed, which can estimate the atomization process of fuel droplets after the wall impingement. The phase-space trajectory of the equation for droplet deformation and oscillation varies from oval to parabola with increasing impact velocity. Four different regimes for droplet diameter distribution are derived from this complex feature of the equation. The amount of liquid film remaining on the wall and the number of droplets are estimated from the related mass and energy conservation laws. The model is called the Oval-Parabola Trajectories (OPT) model in the present report. Comparisons made with some fundamental experimetal data confirm that this mathematical model is effective in a velocity range from 2m/s to 40m/s and in a diameter range below 300 micrometers.