Development of a Control-Oriented Engine Model Including Wave Action Effects

This paper describes the development of a control-oriented model that allows the simulation of the Internal Combustion Engine (ICE) thermodynamics, including pressure wave effects. One of the objectives of this work is to study the effects of a Variable Valve Timing (VVT) system on the behavior of a single-cylinder, four-stroke engine installed on a motor scooter. For a single cylinder engine running at relatively high engine speeds, the amount of air trapped into the cylinder strongly depends on intake pressure wave effects: it is essential, therefore, the development of a model that has the ability to resolve the wave-action phenomena, if successful simulation of the VVT system effects is to be performed. The engine model has been fully implemented in the Matlab-Simulink environment: a zero-dimensional sub-model is used for modeling the cylinder and exhaust manifold thermodynamics, while a one-dimensional model is used for the intake system, in order to take into account the wave action phenomena. The combustion is modeled as a single zone model, with the fuel burning rate described by Wiebe functions. The gas-wall heat transfer calculations are based on Annand heat transfer model for ICE. The gas properties are dependent on temperature and chemical composition of the gas, which are evaluated at each crank-angle. The equations of one dimensional compressible flow in pipes are solved by using the Courant, Isaacson and Rees (CIR) method, and a short description of the boundary conditions is also given. The experimental data needed for model identification are the crank-angle resolved in-cylinder pressure, intake and exhaust manifold pressure, as well as the measurements performed during typical engine-dynamometer steady state tests: rotational speed, load, fuel consumption, Air Fuel Ratio (AFR), ... An automatic procedure for identifying the unknown parameters of the model by using experimental data has also been developed. The Simulink model has been identified and validated by using experimental data acquired on an engine equipped with a traditional valve timing system. It has then been used in order to examine the effects of a VVT system on the amount of air trapped inside the cylinder and on the performance of the engine. The results obtained in simulation have also been compared with the results obtained by using a 1-D commercial code (Ricardo Wave).