Search Results

The introduction of gasoline direct injection (GDI) fuel systems has created numerous technical and manufacturing challenges for fuel system engineers. Direct injection systems run at significantly higher pressures compared to port fuel injection, leading to increased stresses on fuel system components. The demands of GDI pump applications have led to significant innovation opportunities in areas such as high-pressure sealing, control of pumping noise and management of increased loads on pumping elements and pump structure. Shifts in the methodologies for the design of components and materials used, as well as changes to the validation and manufacturing processes, have been required to develop fuel systems for direct injection engines. New technologies for the assembly and joining of materials have also been important to further optimize designs for size, weight, and cost.

An experimental study was conducted to characterize the dynamics and spray behavior of a wide range of minisac and Valve-Covered-Orifice (VCO) nozzles using a high-pressure diesel common-rail system. The measurements show that the resultant injection-rate is strongly dependent on common-rail pressure, nozzle hole diameter, and nozzle type. For split injection the dwell between injections strongly affects the second injection in regards to the needle lift profile and the injected fuel amount. The minisac nozzle can be used to achieve shorter pilot injections at lower common-rail pressures than the VCO nozzle. Penetration photographs of spray development in a high pressure, optical spray chamber were obtained and analyzed for each test condition. Spray symmetry and spray structure were found to depend significantly on the nozzle type.