Three Dimensional Numerical Simulation Of Internal Combustion Engine Cycle

The crisis of energy and the population of environment become a focus recently. Dependent on high thermal efficiency and good economy, the diesel engine is widely used in the world. The key to improve the emission level is to degrade the NO_x and particulate. The main method is to improve the diesel engine combustion to satisfy the strict emission regulations. The diesel engine combustion is a physical and chemic process which is complex and changeable. Experiment is the main combustion research method. The research method used in this thesis is software simulation with FIRE which is developed by the Austrian AVL company. Without the experiment restrict, this software can simulate the combustion in the combustion chamber and get the particular information which is difficult to measure.In this thesis the compression stroke, combustion stroke and expansion stroke of direct injection diesel engine has been simulated. Because there is no intake stroke, details like intake ports and valve are not considered. A simplified geometry is used to reduce the effort for mesh generation. A CFD software (AVL FIRE) was used to study the spray and combustion progress in diesel engines with three different combustion chambers. The in-cylinder flow field, fuel concentration field, temperature field were compared, the influence of mixture formation by different combustion chamber was analyzed. It is found that contracted chamber has preferable mixture and combustion as well as smoke emission than to chamber. The longer swirl persistence and larger turbulence kinetic energy of the contracted chamber are propitious to mixture formation, so it enhances the diffuse combustion and improve the combustion character. The impenetrate length is longer because the in-cylinder flow field of ω chamber is less intensive, which explains the amount of rich fuel-air mixture near the wall and the combustion chamber is easier to burn out. The influence has been studied in this thesis which is the injection timing, EGR ration, the intake temperature and multiple injection on the NO_x and particulate in diesel engine emissions.