Combustion Engine Air Intake Theoretical Modelling, Model-Verfication & Application to Optimal Valve Actuation

Abstract

AbstractA theoretical model for the air intake of a four stroke internal combustion engine is derived from first principles, the conservation of mass and the conservation of energy. Full valve actuation is taken into account: The opening angle of both the intake as well as the exhaust valve, as well as the variable valve lift are considered as plant inputs, which may be manipulated to maximize the air intake rate and hence the power, the engine delivers. The theoretical model is verified by comparing the model output to steady state data collected at an engine test bench. Therefor a formal connection between state-of-the-art mean value models and the crank angle resolved physical model must be established. The pressure loss in the intake valve is considered a disturbance of the ideal cylinder filling dynamics, which is estimated using non-linear optimization techniques. The intended purpose of physical model building for the cylinder air intake is prediction of the air intake rate and computation of optimal valve control action before a lot of effort is put into a real experiment at the engine test bench. A significant reduction of operating time and cost consumed by the real engine test bench can be achieved, if a small subset of steady state measurements are used to compute a meta-model for the pressure loss. The combination of the black-box pressure loss model and the air intake model allows for prediction of the air intake rate at unknown operating points of the engine with sufficient accuracy.