An Integrated System of Models for Performance and Emissions in SI Engines: Development and Identification

An integrated system of phenomenological models is applied in conjunction with identification techniques to simulate SI engine performance and emissions. In the framework of a hierarchical model architecture, the model structure provides the steady state engine data required for the design and validation of synthetic engine models. This approach allows limiting the recourse to the experimental data and speeds up the engine control strategies prototyping.

The model structure is composed of a multi-zone thermodynamic engine model linked to a 1-D commercial fluid-dynamic model for intake and exhaust gas flow and to a physical model for NO_x exhaust emissions. In order to improve model accuracy and generalization, an identification methodology is applied to estimate the optimal parameters for the turbulent combustion model. Due to the built-in physical content, the proposed methodology requires a relatively limited amount of experimental data for characterizing the under-study engine. Thus it can be extensively used to provide the engine performance and emission data for training the synthetic models usually adopted for engine control application.

The model structure has been tested on a commercial 4 cylinders - 1.2 liters SI engine, with statisfactory accuracy in predicting engine performance and emissions. Furthermore the identification process has allowed deriving a functional expression of some of the model parameters vs. engine operating conditions.