Simulating Calculation Of High Pressure Injection Process Of Diesel Engine Based On MATLAB

In the face of the increasingly stringent emission regulations in many countries, besides optimizing turbocharged system and developing advanced exhaust back disposal, improving combustion should also be taken into account to keep diesel engine's important status in traffic field. Fuel injection system is the key factor that affects combustion process of the engine, so it is very important to analyze fuel injection system characteristics in theory, especially at present, adopting model to simulating fuel injection progress is a significant research task. Based on the related literatures, the structures and the features of the pump-tube-nozzle fuel injection system are introduced in detail. The meaning of simulation and development of the correlative technology of the fuel injection system are also described. A mathematic model of pump-tube-nozzle fuel injection system is created according to its geometry structure and the dynamic principle of the pressure wave spread. An improved simulating calculation method is introduced in the solution of the flowing equations of high pressure pipe, and the effect of continuous change of the fuel characteristics to the wave movement should be considered. After partition the pipe into calculation cells, the sound velocity, fuel density, fuel pressure and flowing velocity at every calculation crunode in different time are gained. The difference equations for numerical solution of boundary conditions in pump and nozzle are given. The characteristics of MATLAB and programming language are also introduced. According to the simulation method bring forward, the simultaneous equations of the conservation of mass equations, the dynamics equations of moving parts and the pressure wave equations in all boundaries are solved. The pressure curves in the pump house, delivery valve house, high-pressure fuel pipe and the nozzle house and the principle of the fuel flowing are gained. Finally, the simulation results are compared with the example and analyzed the reasons of twice injection and cavitations including proving the validity of the calculation method.