Study of Injection Strategies of Two-stage Gasoline Direct Injection (TSGDI) Combustion System

Gasoline Direct Injection (GDI) engines developed at nineties of the twentieth century can greatly improve the fuel economy. But the combustion chamber design and mixture control of the engines are very complex compared with Port Fuel Injection (PFI) gasoline engines. A two-stage gasoline direct injection (TSGDI) combustion system is developed and aimed to solve the problem of the complexity. Two-stage fuel injection and flexible injection timings are adopted as main means to form reasonable stratified mixture in the cylinder. A simple combustion chamber and helical intake port are designed to assist the mixture's stable combustion, which reduces the difficulties of the combustion system design.

Systematical simulation and experimental studies of the effects of injection strategies such as different first,second injection timings and injection ratios, on the mixture formation processes and engine performanc are made in detail. The experimental results are analyzed combined with the simulations and the two results agree well. After the optimization of the injection parameters and other parameters, the TSGDI engine's fuel consumption can reduce 13%∼24% or so compared to the common PFI gasoline engines.