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A phenomenological heat transfer model for direct injection diesel engines has been developed. Utilizing the thermodynamic results of a combustion model as an input, the model is able to predict the temporal variation of the heat losses from the cylinder gas to the cylinder walls. Additionally, the division into isothermal combustion chamber subsurfaces allows the consideration of the spatial variation of the wall heat fluxes. The physical mechanisms such as flow dependent convection, heat radiation due to hot soot particles and isolation effects of deposited soot layers are described in detail. Thus, the effects of these mechanisms on the overall heat transfer can be studied. The heat transfer model was verified successfully by comparison to measured wall heat fluxes in a single-cylinder direct injection diesel engine. It is shown that the effects of engine speed and load, turbo-charging and soot deposition can be predicted with good accuracy.

Two of the objectives in developing internal-combustion engines are to keep wear and - at the same time - the related friction losses between the piston rings and cylinder liner as low as possible. To this end, optimization of the hydrodynamic conditions and designing for reduction of mixed friction have become the goals of many engine manufacturers and developers. As part of this project, a two-dimensional computation model is developed to include modelling of four areas: gas dynamics, lubrication-oil hydrodynamics, solid-body contact, and piston-ring dynamics. The gas pressures in the ring pack are calculated either using the one-dimensional Navier-Stokes equation or the unsteady adiabatic-flow model. The hydrodynamic pressure distribution ranging from the piston-ring running surface to the cylinder wall is calculated by solving Reynold's differential equation for rough surfaces /1/. This was accomplished under the use of flow factors.