It is well known that in automotive applications problems
related to control and management are nowadays of paramount
importance to improve engine performance and to reduce fuel
consumption and pollutant emissions. In the design of control and
diagnostics systems, the use of theoretical models proved to be
very promising, also to reduce development time and costs, as
widely documented in the open literature. From this point of view,
the complexity of actual engines due both to the continuous
enhancement of existing subsystems (e.g., turbochargers, exhaust
gas recirculation systems, aftertreatment components, etc.) and to
the introduction of specific devices (e.g., Variable Valve
Actuation systems) give rise to challenging issues in modeling
development and applications.
The paper describes a theoretical model of an automotive engine
built up starting from the original library developed in Simulink®
by the authors for the simulation of last generation automotive
engines. The tool was used in former works to build up Mean Value
Models (MVMs) of automotive engines for "real-time"
simulations, which were used in Hardware-in-the-Loop (HiL)
applications. The model proposed in this work is an enhancement of
the mentioned ones to allow for "crank-angle" simulations
of engine thermodynamic processes. To this extent several blocks
were built up for the simulation of intake and exhaust valves (with
user-defined lift curves and variable actuation) and of in-cylinder
processes. Combustion process has been described following a
classic single-zone approach based on a proper Heat Release Rate
(HRR). Other components of the intake and exhaust systems were
modeled by using the original library blocks.
Through a specific calibration procedure, the model was fitted
on the typical layout of an automotive SI engine allowing for
steady and transient simulations of the engine behavior. Calculated
results are compared in the paper with available experimental data,
showing a good agreement.