Comparison of Combustion and Pollutant Emission Models for DI Diesel Engines

In this work two significant approaches with different level of complexity for Diesel combustion modeling have been analyzed and implemented by the authors in the same open-source code, OpenFOAM: the Eddy Dissipation model and the PaSR (Partially Stirred Reactor) model. Concerning the latter, the potentialities and accuracy of the ISAT (In-Situ Adaptive Tabulation) algorithm, recently implemented by the authors into OpenFOAM, to reduce significantly the required computational time, were evaluated. Similarly, different models to predict pollutant emissions are revised and tested, due to considering the need to fulfill the future emission regulations imposing further reductions in NO_x and soot.

The mentioned models were applied to simulate a selection of significant Constant-Volume Diesel Combustion test-cases from the Engine Combustion Network database [1]. These data are particularly worth of interest since they have a public domain access, providing a framework for collaborative comparisons, and they include detailed information about pressure rise, liquid penetration length, ignition delay, lift-off length and soot distribution. The selected and simulated conditions consider n-heptane as fuel and include different oxygen concentrations and thermodynamic states (ambient density and temperature). Finally a real engine configuration was considered and the obtained results were compared against cylinder pressure data and pollutant concentrations.