Influence of turbulence-radiation interactions in engine radiation heat transfer

Detailed radiation modelling in advanced high-efficiency piston engines is recently getting attention due to the trends toward higher operating pressures and higher levels of exhaust gas recirculation (EGR), which makes molecular gas radiation more prominent (absorption coefficient proportional to participating species concentration). 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. Hence, here line-by-line (LBL) spectral radiation property model and photon Monte Carlo (PMC) radiative transfer equation (RTE) solvers have been implemented in an OpenFOAM-based engine CFD code. The influence of turbulence-radiation interactions (TRI) is determined by comparing results obtained using local mean values of composition and temperature to compute radiative emission and absorption with those obtained using a particle-based transported probability density function (tPDF) method. Simulations have been performed for a full-load (peak pressure ∼200 bar) heavy-duty diesel engine. Differences in computed NO and soot levels and wall heat transfer rates are shown for cases with and without TRI. Computed radiative emission and reabsorption with TRI are higher compared to those obtained from a no-TRI case for the same operating condition. With consideration of TRI, the net radiative heat loss is lower than for the no-TRI case for the same operating condition. With TRI, radiative emission from gases and soot both increase-. However, the increase in soot emission is more prominent than in gas emission.