Theoretical Analysis of Diesel Engine NOx and Soot with Heuristic Macro-Parameter-Dependent Approach and Virtual Multi-Zone Real Time Models

With more stringent emissions regulations, effective emission modeling on NOx and soot for both on-road and off-road diesel engines becomes increasingly important for diesel engine system design and real-time engine controls. In this paper, a heuristic macro-parameter-dependent approach is proposed by combining theoretical analysis with semi-empirical method. The proposed modeling approach is different from the existing methods, such as empirical modeling, phenomenological modeling, and three-dimensional KIVA modeling. The proposed model uses the macro parameters of engine performance, both cycle-average (e.g., air-to-fuel ratio, EGR rate) and in-cylinder instantaneous data (e.g., cylinder pressure trace) as input. The model computes NOx and soot as a function of crank angle. A concept of “time-variant virtual space zones (burning, burned, and unburned)” is proposed based on the fraction of fuel burnt. The fundamental theory of soot formation and oxidation processes was applied in the soot model. Soot formation and oxidation was successfully decoupled to make the modeling convenient and effective. A major advantage of the proposed models is that emissions modeling can be conducted by using algebraic equations in real-time. And this makes the approach especially suitable and attractive for engine system design and for real-time emissions-related electronic controls.