Systematic Uncertainty Considerations in the Comparison of Experimental and Computed Cylinder Pressure and Heat Release Histories

Computational simulations of engine combustion processes are increasingly relied upon to lead the design of advanced IC engines. Both computational fluid dynamics (CFD) simulations as well as thermodynamics-based phenomenological 0D or 1D gas dynamics simulations are examples of current simulation strategies. Before simulations can be utilized to guide the design process, they must be validated with experimental results. Typically, the experimental data used for validation of computational simulations include in-cylinder pressure and apparent heat release rate (AHRR) histories. However, the process of comparison of experimental and simulated pressure and AHRR curves is largely qualitative; therefore, the validation process is mostly visual. In the present work, the authors introduce a framework for quantifying uncertainties in experimental pressure data, as well as uncertainties in the “average” AHRR curve that is derived from ensemble-averaged cylinder pressure histories. Predicted AHRR curves from CFD simulations are also quantitatively compared with the experimental AHRR bounded by “uncertainty bands” in the present work.