Numerical Simulation of Turbulent Combustion in Internal Combustion Engines

The combustion process in internal combustion engines can occur in multiple modes. In spark-ignition (SI) engines it is mainly a turbulent premixed flame propagation process; however, since the charge is at elevated temperature and pressure, it is possible to have autoignition in the unburned charge, which can lead to engine knock. In conventional Diesel engines, the combustion process is first started with the onset of ignition and followed by turbulent diffusion flames. In the development of modern compression ignition engines, the tendency is to use a mixed mode combustion in order to reduce soot and NOx emissions. Examples of such engine concepts are homogeneous charge compression ignition (HCCI), reactivity controlled compression ignition (RCCI), and partially premixed combustion (PPC) engines. To meet the challenge of high-performance numerical simulations in today’s engine design it is necessary that the simulation models shall handle the different modes of combustion. In this chapter, the various combustion modes will be reviewed. Recent simulation results that reveal the finely detailed reaction zone structures in HCCI, RCCI, and PPC engines will be discussed. The challenges in the modeling of multiple modes combustion in internal combustion engine will be discussed in the frameworks of large-eddy simulation and Reynolds-averaged Navier–Stokes simulations. Finally, state-of-the-art models for the various combustion modes will be reviewed, focusing on the modeling of multimodes combustion problems.