Numerical Simulation Of The Combustion In 135-Diesel Engine

The combustion process of internal combustion engine has great effects on the performance of it. High efficient combustion is the crucial element of increasing power and decreasing fuel consumption and emission. In DI diesel engine the mixing of fuel and air influences the combustion highly and the quality of the mixture depends on fuel injection parameters and the flow in cylinder to a great extent. So it has momentous significance to study the effects of fuel injection parameters and intake pipe structure on the combustion process. As the developments of science and technology, the 3-dimensional numerical simulation of engine working process has been playing its role in forecasting the performance of diesel engine and guiding the design of combustion system. When choosing the optimum parameters at the beginning of design process, the simulation can replace some part of engine experimentation. As a result we can greatly reduce the development research periods and decrease the development cost.In this paper the all-purpose CFD software STAR-CD is introduced to simulate the intake, compress, injection and combustion processes of a two-valve diesel engine with different injection timings, different number of nozzle holes and different nozzle extruding lengths. After getting the exact and detailed transient information in the cylinder, the effects of the above fuel injection parameters are analyzed. The calculating results show that: injection timing, number of nozzle holes and nozzle extruding length can greatly influence fuel-air mixing process by affecting ignition delay period, spray distribution and fuel drop diameters. So fuel-air mixing quality can be ameliorated if the above parameters are selected appropriately, and therefore combustion process will be improved.After summarizing the effects of fuel injection parameters on the combustion, the diesel engine is reconstructed with 4 valves and a new type of intake pipe structure is designed for it. Then the three-dimensional numerical modeling of engine working process is introduced again for the 4-valve diesel engine. Finally through comparing with 2-valve diesel engine, it is confirmed that the 4-valve diesel engine has a batter performance.