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A Parametric Model for Ionization Current in a Four Stroke SI Engine

A Parametric Model for Ionization Current in a Four Stroke SI Engine J. Dyn. Sys., Meas., Control -- March 2009 -- Volume 131, Issue 2, 021001 (11 pages) doi:10.1115/1.3023119 Author(s): Ingemar Andersson Signal Processing Group, Department of Signals and Systems Chalmers University of Technology, Gothenburg SE-41296, Sweden Lars Eriksson Vehicular Systems, Department of Electrical Engineering Linkoping University, Linkoping SE-58183, Sweden Abstract: A model for the thermal part of an ionization signal is presented that connects the ionization current to cylinder pressure and temperature in a spark ignited internal combustion engine. One strength of the model is that, after calibration, it has only two free parameters: burn angle and initial kernel temperature. By fitting the model to a measured ionization signal, it is possible to estimate both cylinder pressure and temperature, where the pressure is estimated with good accuracy. The model approach is validated on engine data. Cylinder pressure and ionization current data were collected on a Saab four-cylinder spark ignited engine for a variation in ignition timing and air-fuel ratio. The main result is that the parametrized ionization current model can be used to estimating combustion properties as pressure, temperature, and content of nitric oxides based on measured ionization currents. The current status of the model is suitable for off-line analysis of ionization currents and cylinder pressure. This ionization current model not only describes the connection between the ionization current and the combustion process, but also offers new possibilities for engine management system to control the internal combustion engine.

Ingemar Andersson and Lars Eriksson

ASME Journal of Dynamic Systems, Measurement, and Control, 2009

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