Main role of fuel rail for GDI (Gasoline Direct Injection) system is to store and distribute gasoline between high pressure pump and injector. Under the engine operating condition, fuel pressure and ambient temperature are applied to fuel rail as fatigue load, which can cause fatigue failure.
To meet current a global environmental regulation, a fuel injection pressure is gradually increasing. Therefore a fuel rail for GDI engine which is installed between fuel pump and injector must be stronger than now. Also the target reliability of the fuel rail has to be increased than before.
Accordingly, fatigue behaviors of fuel rail must be analyzed and expected at the development stage.
In this study, a procedure for assessment the fatigue life of GDI fuel rail was developed. With this, fatigue load on the GDI fuel rail can be expected under actual vehicle operating conditions. Furthermore, fatigue life of a part can be verified based on the expected fatigue load. To establish certain process, pressure and temperature on fuel rail were measured under actual vehicle operating conditions. Afterwards, measured data was extrapolated to product warranty with probabilistic method and damage model specified. By applying obtained result, fatigue test mode was designed for fuel rail reliability target.
Finally, fatigue life of next generation fuel rail was expected by modifying and expanding an existing data and using above procedure.