Radiation in piston engines has received relatively little attention to date. Recently, it is being revisited in light of current trends towards higher operating pressures and higher levels of exhaust-gas recirculation (EGR), both of which enhance molecular gas radiation. Advanced high-efficiency engines also are expected to function closer to the limits of stable operation, where even small perturbations to the energy balance can have a large influence on system behavior. Here several combinations of spectral radiation property models and radiative transfer equation (RTE) solvers have been implemented in an OpenFOAM-based engine CFD code, and results of preliminary simulations with coupled radiation models are presented for a heavy-duty diesel engine at a part-load no-EGR operating condition. The most important influences on computed emissions and heat losses are found to be those of spectral radiation properties and unresolved turbulent fluctuations in composition and temperature, although overall radiation effects are relatively small for this operating condition. The models are being applied to other operating conditions where radiation effects are expected to be more prominent.
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