GENERAL THERMODYNAMIC ANALYSIS FOR ENGINE COMBUSTION MODELING.

The energy and entropy balance equations in an open control volume are treated analytically by a method that can be applied to any level of modeling of any internal combustion engine. The method involves no major assumptions. The result is in the form of differential equations for the instantaneous mass fraction of burnt gas mixture and for the entropy generated by irreversibility within the chosen control volume, in terms of the pressure and volume histories and appropriately defined mean variables. The choice of control volume may range from the entire combustion chamber to a single mesh point in a numerical solution scheme. Irrespective of the level of detail of the chosen modeling approach, the entropy balance equation provides an interesting and useful, though very seldom exploited, independent relation to check the consistency of any set of additional modeling assumptions or closure scheme with the second law requirement of nonnegativity of the local and global rate of entropy production by irreversibility.