Modeling of combustion chamber convective heat transfer for internal combustion engines

An investigation of multi-dimensional turbulence models for calculating engine in-cylinder convective heat transfer was performed. Separate analyses of turbulent transport in the bulk flow and near wall regions were made.; Calculations showed the commonly used {dollar}k - epsilon{dollar} model to be deficient in several areas that are important for in-cylinder flows. Separate modifications to the model for separated shear layer and swirling flows were successfully formulated.; An alternative near wall turbulence model was developed. The new model, designated the boundary layer wall model, solves a set of boundary layer equations on a separate grid. The wall layer flow solution does not rely on the assumption of turbulence equilibrium or prescribed mean flow behaviour. Simulations covering a wide range of complex flow conditions demonstrated that the new model consistently outperforms conventional wall functions.; Using the new modeling methodology, a study of low heat rejection (LHR) engine heat transfer was performed in order to understand the effects of elevated wall temperatures on in-cylinder heat loss. The focus was on two mechanisms for enhancing heat transfer in the presence of high surface temperatures which were thought to play an important role in determining the heat loss from LHR engines. They are steepening of wall layer temperature gradients due to piston-induced compression heating and increasing wall layer penetration of burned gases due to a reduction in flame quench distance.; The analysis demonstrated that neither near wall gas compression heating nor thinning of the flame quench region can cause heat transfer to increase with wall temperature. This result directly contradicts recent controversial experimental studies and supports the view that insulating the combustion chamber will reduce in-cylinder heat loss and thereby improve engine efficiency.