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A personal computer-based transient simulation model has been developed to predict heavy tracked vehicle performance and fuel consumption under accelerating conditions. The model consists of a transient engine model, a transient powertrain model and a driving resistance model. Engine dynamics, turbocharger dynamics and governor dynamics are related with throttle position, clutch pedal and gear lever, and the effects of these factors on vehicle transient behavior are formulated. Engine transient performance is calculated based on the cycle by cycle analysis of engine running processes. The computer simulation has been implemented for a 5-speed manual-transmission heavy tracked vehicle, and is validated by comparing the predicted values with the measured data. The vehicle accelerating performance and fuel consumption have also been calculated by using the engine maps based on the steady-state experiments.

This paper describes the development of a numerical optimization technique for in-cylinder processes of SI engines, which consists of an in-cylinder processes model and an optimization model. The in-cylinder processes model simulates the full thermodynamic cycle containing spark ignition, turbulent flame propagation, heat release, nitric oxide emission and knock. The optimization model uses a nonlinear mathematical programming method, in which effective specific fuel consumption, NO emission and knock index are respectively regarded as objective function or constraint function, spark timing, compression ratio, equivalence ratio and valve timings as independent variables. The numerical optimization for a SI engine is carried out and is validated by experimental result. The engine performances are evidently improved by the optimization.