Many of the approaches to diagnostics of in-cylinder spatially resolved quantities (such as equivalence ratio, temperature, speciation, etc.) require either optical engines or computational fluid dynamics. These approaches are expensive (time or money) and will likely never be practical for on-board use in the future. The market trend towards real-time control and consumer grade in-cylinder pressure transducers suggest that relatively simple modeling techniques based on cylinder pressure and other standard engine sensors are well situated to be a part of the future engine control schemes. This work expands previous efforts to calculate combustion trajectories (path through equivalence ratio vs. temperature plane) based on cylinder pressure measurements in near real-time.
This work incorporates the current state-of-the-art diesel fuel spray mixing models (Kattke and Musculus entrainment waves) and adds features to accounting for changing cylinder pressure, adaptive time step based on sampling rate of cylinder pressure, and optimizing spray axial resolution for reduced calculation time. Based on the predicted local fuel concentration, flame temperature and relating calculated heat release rates to the amount of fuel burned in each portion of the spray the combustion processes can be tracked to give a cumulative history of the ignition, subsequent mixing and heating/cooling that gives a picture of what combustion looks like on the equivalence ratio vs. temperature plane.
Various engine operating conditions are explored including conventional diesel operation with and without EGR as well as highly dilute late injection low temperature combustion at different injection pressures. The results obtained in this work give encouragement that this type of approach may enable future engine control using these detailed yet computationally simple approaches.