Linköping Studies in Science and Technology Thesis No. 1104 A Specific Heat Ratio Model and Compression Ratio Estimation Marcus Klein Division of Vehicular Systems Department of Electrical Engineering Linköping University, SE–581 83 Linköping, Sweden http://www.vehicular.isy.liu.se/ Email:
[email protected] Linköping 2004 A Specific Heat Ratio Model and Compression Ratio Estimation °c 2004 Marcus Klein Department of Electrical Engineering, Linköping University, SE–581 83 Linköping, Sweden. ISBN 91-7373-992-8 ISSN 0280-7971 LiU-TEK-LIC-2004:33 Printed by UniTryck, Linköping, Sweden 2004 To Sofia and Ebba Abstract Cylinder pressure modeling and heat release analysis are today important and standard tools for engineers and researchers, when developing and tuning new engines. An accurate specific heat ratio model is important for an accurate heat release analysis, since the specific heat ratio couples the systems energy to other thermodynamic quantities. The objective of the first part is therefore to investigate models of the specific heat ratio for the single-zone heat release model, and find a model accurate enough to introduce a cylinder pressure modeling error less than or in the order of the cylinder pressure measurement noise, while keeping the computational complexity at a minimum. As reference, a specific heat ratio is calculated for burned and unburned gases, assuming that the unburned mixture is frozen and that the burned is at chemical equilibrium. Use of the reference model in heat release analysis is too time consuming and therefore a set of simpler models, both existing and newly developed, are compared to the reference model.