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This study simulates soot formation processes in diesel combustion using a large eddy simulation (LES) model, based on a one-equation subgrid turbulent kinetic energy model. This approach was implemented in the KIVA4 code, and used to model diesel spray combustion within a constant volume chamber. The combustion model uses a direct integration approach with a fast explicit ordinary differential equation (ODE) solver, and is additionally parallelized using OpenMP. The soot mass production within each computation cell was determined using a phenomenological soot formation model developed by Waseda University. This model was combined with the LES code mentioned above, and included the following important steps: particle inception during which acenaphthylene (A 2 R 5 ) grows irreversibly to form soot; surface growth with driven by reactions with C 2 H 2 ; surface oxidation by OH radical and O 2 attack; and particle coagulation.The results obtained using our new model are compared to those generated using a RANS (RNG k-epsilon) model, and also to experimental data from the engine combustion network (ECN) of Sandia National Laboratories. The sensitivity of the LES results to mesh resolution is also discussed. The results show that both RANS and LES simulations predict the dispersion and vapor penetration of the injected fuel fairly well. LES generally provides flow and spray characteristics in better agreement with experimental data than RANS. It is also shown that the phenomenological soot model is useful for investigating soot particle production and distribution. The LES model was better than the RANS model at describing instantaneous soot concentration contour.

The first objective of this work is to develop a numerical simulation model of the spark ignited (SI) engine combustion, taking into account knock avoidance and heat transfer between in-cylinder gas and combustion chamber wall. Secondly, the model was utilized to investigate the potential of reducing heat losses by applying a heat insulation coating to the combustion chamber wall, thereby improving engine thermal efficiency. A reduction in heat losses is related to important operating factors of improving SI engine thermal efficiency. However, reducing heat losses tends to accompany increased combustion chamber wall temperatures, resulting in the onset of knock in SI engines. Thus, the numerical model was intended to make it possible to investigate the interaction of the heat losses and knock occurrence. The present paper consists of Part 1 and 2. Part 1 deals with the description of the numerical model and the fundamental characteristics of instantaneous temperature swings in the combustion chamber wall.The numerical model is developed by utilizing GT-POWER combined with three sub-models; a non-dimensional two-zone combustion model, an autoignition model in the unburned gas and an instantaneous heat transfer model in the combustion chamber wall. The combustion model considers the flame speeds affected by the in-cylinder conditions. The Shell model was utilized to predict autoignition. The heat transfer model in the combustion chamber wall calculates the instantaneous one-dimensional thermal conductivity, and further predicts wall surface and inside temperatures. The fluctuation range of calculated temperature swings is reasonably similar to measured data obtained in previous studies.

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