Fast algorithms for generating thermal boundary conditions in combustion chambers

The focus of this paper is the fast determination of thermal boundary conditions in engine combustion chambers. In contrast with many other studies, only cycle integrated quantities like the induced torque are needed as input variables, which means that no crank angle resolved in-cylinder pressure data are required. Changes in the engine mapping like variations in ignition time and boost pressure or various lambda strategies are studied concerning component temperatures, and not to crank angle resolved heat fluxes, as it was often the case in previous published works. It is demonstrated that variations of cycle averaged solid temperatures can be predicted with the proposed identification method for thermal boundary conditions. The limit of the model for highly non-uniform pressure changes, as it is the case in ignition time variations, is well discussed. A variety of thermal boundary conditions is tested within a CFD-CHT simulation in order to get component temperatures. The new calculation algorithm combines proven models according to Woschni with a statistical method, which takes pressure fluctuations into account. Probability density functions and realisations of chosen random variables, like heat transfer coefficients, are transformed according to different engine operating conditions. For model validation, engine temperature measurements are conducted.