Lund Reports on Combustion Physics, LRCP-80

The ionization sensor is an electrical probe for diagnostics in internal com-bustion engines. The combustion process aects the electrical properties of the gas in the cylinder. Thus the sensor signal contains copious information about the conditions in the combustion chamber. A thorough characterization of the sensor makes it possible to take advantage of a larger portion of this information for feedback control of the engine. The present work focuses on the identication of the basic mechanisms governing the functioning of the ionization sensor and their interaction. Optical diagnostics, equilibrium analysis and an elementary model have been employed to characterize the sensor. It was found that the contact between ame front and cathode as well as the mixture composition along the main current path governs the sensor signal during early combustion. On the basis of these ndings, a zone-based model for the sensor was suggested