Modelling the effects of combustion and turbulence on near-wall temperature gradients in the cylinders of spark ignition engines

An existing quasi-dimensional engine cycle model has been modified to enabl e accurate prediction of the near-wall temperature field in the burned and unburned gases. This has been achieved by dividing the cylinder into a numb er of discrete masses, each of which has a unique state. These discrete mas ses are assumed to remain stacked in layers adjacent to the cylinder walls in both the unburned gas and in the discrete segments generated during the sequential burning process. A k-epsilon turbulence model has been incorpora ted into the engine cycle simulation, providing information on the nature o f the instantaneous in-cylinder turbulence for input to a fractal flame mod el to depict the flame propagation process. When this approach is applied t o the prediction of the flame propagation rate, excellent comparison is aff orded between simulated and measured pressure-crank angle diagrams. Further validation is provided by comparison of near-wall temperature predictions with measured ones and the essential features of the observed boundary laye r behaviour are reproduced.