This project deals with the numerical setup about the effect of different mixture properties of premixed combustion material using Computational Fluid Dynamic (CFD). Mitsubishi Magma 4G15 is used as the base line engine design for the simulation model. 2000 revolution per minute (rpm) and 1000 iterations are set as the tested speed and the number of iterations per time step respectively. The simulation is started right before the spark ignited and when both valves are closed. The model is simulated at different mixture properties which are constant and varying mixture properties. The constant mixture properties value is taken from previous study. While the varying mixture properties is simulated using kinetic theory where only specific heat, thermal conductivity, and viscosity are varied. Case 1 is set as the constant mixture properties and also as the benchmark case. Case 2 until case 5 is the varying mixture properties with different value of L-J parameters. Case 1 gives only 2.19% of deviation from the experimental result on the peak pressure value and 25% deviation on the peak pressure timing. Meanwhile, for case 2 until case 5, they give as much as 22.34% until 45% deviation on peak pressure value and 100% until 162.5% deviations on the peak pressure timing. The key parameter that caused the results are the L-J parameters, mass fraction burned, and turbulence flame speed. The inaccuracy of the turbulence speed is mostly based on laminar flame speed, thermal conductivity, and specific heat. So, the study of L-J parameter is needed to ensure the perfect result in using kinetic theory approach.

This thesis deals with the flame propagation in spark ignition engine combustion process using Computational Fluid Dynamic (CFD). This study is based on flame propagation inside the combustion chamber which is important as flame propagation affects the engine efficiency, emission and some more. A 3-D model is created based on the Mitsubishi Magma 4G15 that act as a baseline engine. It is then simulated using CFD where its approaches make it a suitable platform to study the internal combustion engine phenomenon. The project simulates only 50o CA starting from the ignition until the completion of the combustion process. The flame radius obtain through simulation is then compared with the experimental data together with the literature review. However, there are discrepancies of the results due to improper boundary condition and inherit limitation of the model. For further simulation of combustion process must consider detail mixture properties, detail boundary condition and model extension for better accuracy data.

A systematic control of mixture formation with modern high-pressure injection systems enables us to achieve considerable improvements of the combustion pr- ess in terms of reduced fuel consumption and engine-out raw emissions. However, because of the growing number of free parameters due to more flexible injection systems, variable valve trains, the application of different combustion concepts within different regions of the engine map, etc., the prediction of spray and m- ture formation becomes increasingly complex. For this reason, the optimization of the in-cylinder processes using 3D computational fluid dynamics (CFD) becomes increasingly important. In these CFD codes, the detailed modeling of spray and mixture formation is a prerequisite for the correct calculation of the subsequent processes like ignition, combustion and formation of emissions. Although such simulation tools can be viewed as standard tools today, the predictive quality of the sub-models is c- stantly enhanced by a more accurate and detailed modeling of the relevant pr- esses, and by the inclusion of new important mechanisms and effects that come along with the development of new injection systems and have not been cons- ered so far. In this book the most widely used mathematical models for the simulation of spray and mixture formation in 3D CFD calculations are described and discussed. In order to give the reader an introduction into the complex processes, the book starts with a description of the fundamental mechanisms and categories of fuel - jection, spray break-up, and mixture formation in internal combustion engines.

The virtual development of future Spark Ignition (SI) engine combustion processes in three-dimensional Computational Fluid Dynamics (3D-CFD) demands for the integration of detailed chemistry, enabling - additionally to the 3D-CFD modelling of flow and mixture formation - the prediction of fuel-dependent SI engine combustion in all of its complexity. This work presents an approach, which constitutes a coupled solution for flame propagation, auto-ignition, and emission formation modelling incorporating detailed chemistry, while exhibiting low computational costs. For modelling the regular flame propagation, a laminar flamelet approach, the G-equation is used. Auto-ignition phenomena are addressed using an integrated flamelet approach, which bases on the tabulation of fuel-dependent reaction kinetics. By introducing a progress variable for the auto-ignition - the Ignition Progress Variable (IPV) - detailed chemistry is integrated in 3D-CFD. The modelling of emission formation bases on an interactively coupled flamelet approach, the Transient Interactive Flamelet (TIF) model. The functionality of the combined approach to model the variety of SI engine combustion phenomena is proved first in terms of fundamentals and standalone sub-model functionality studies by introducing a simplified test case, which represents an adiabatic pressure vessel without moving meshes. Following the basic functionality studies, the sub-model functionalities are investigated and validated in adequate engine test cases. It is shown, that the approach allows to detect locally occurring auto-ignition phenomena in the combustion chamber, and to model their interaction with regular flame propagation. Moreover, the approach enables the prediction of emission formation on cell level.

This book contains the theory and computer programs for the simulation of spark ignition (SI) engine processes. It starts with the fundamental concepts and goes on to the advanced level and can thus be used by undergraduates, postgraduates and Ph. D. scholars.

Downsizing of modern gasoline engines with direct injection is a key concept for achieving future CO22 emission targets. However, high power densities and optimum efficiency are limited by an uncontrolled autoignition of the unburned air-fuel mixture, the so-called spark knock phenomena. By a combination of three-dimensional Computational Fluid Dynamics (3D-CFD) and experiments incorporating optical diagnostics, this work presents an integral approach for predicting combustion and autoignition in Spark Ignition (SI) engines. The turbulent premixed combustion and flame front propagation in 3D-CFD is modeled with the G-equation combustion model, i.e. a laminar flamelet approach, in combination with the level set method. Autoignition in the unburned gas zone is modeled with the Shell model based on reduced chemical reactions using optimized reaction rate coefficients for different octane numbers (ON) as well as engine relevant pressures, temperatures and EGR rates. The basic functionality and sensitivities of improved sub-models, e.g. laminar flame speed, are proven in simplified test cases followed by adequate engine test cases. It is shown that the G-equation combustion model performs well even on unstructured grids with polyhedral cells and coarse grid resolution. The validation of the knock model with respect to temporal and spatial knock onset is done with fiber optical spark plug measurements and statistical evaluation of individual knocking cycles with a frequency based pressure analysis. The results show a good correlation with the Shell autoignition relevant species in the simulation. The combined model approach with G-equation and Shell autoignition in an active formulation enables a realistic representation of thin flame fronts and hence the thermodynamic conditions prior to knocking by taking into account the ignition chemistry in unburned gas, temperature fluctuations and self-acceleration effects due to pre-reactions. By the modeling approach and simulation methodology presented in this work the overall predictive capability for the virtual development of future knockproof SI engines is improved.