3-D Numerical Simulation On The Working Process Of A Gasoline Direct Injection Engine

Compared with conventional Port Fuel Injection (PFI) gasoline engine, GDI (Gasoline Direct Injection) engine has advantages of higher fuel economy. To control the fuel air mixing process exactly and ensure the appropriate concentrations of the mixture around the spark plug are the core technical issue of GDI. With the aid of CFD software packages, researchers can understand the working process of the GDI engine and optimize the design and control strategies of the engine.The working process of a gasoline direct injection engine, which was developed by the R&D Center of FAW Group, was simulated with a 3-D CFD package. The movement of working fluid in the intake ports, exhaust ports and cylinder of the engine was analyzed. The fuel injection, fuel-air mixture formation and combustion processes of two injection strategies and the spray angle were compared and analyzed.This thesis shows that slighter rich mixture with fuel air equivalence ratio of 1.1 can be formed around the spark plug at the ignition timing when the injection duration is 111℃A and the fuel injection timing is 420°CA in the condition of given spray pressure and designed injector. The uniformity of the mixture of this case is better compared with fuel injection timing of 390℃A. Meanwhile, the mixture of this case is easier to be ignited and flame propagation is faster. With faster combustion rate, shorter rapid combustion period and higher peak pressure, the engine would have better combustion performance.The 3-D numerical simulation in this thesis provides significant information about mixture formation and combustion processes in cylinder, which is great helpful to optimization of the gasoline direct injection engine.