The large eddy simulation (LES) with Volume of Fluid (VOF) interface tracking method in Ansys-FLUENT has been used to study the effects of nozzle hole geometrical parameters on gasoline direct injection (GDI) fuel injectors, namely the effect of inner hole length/diameter (L/D) ratio and counter-bore diameters on near field spray characteristics. Using iso-octane as a model fuel at the fuel injection pressure of 200 bar, the results showed that the L/D ratio variation of the inner hole has a more significant influence on the spray characteristics than the counter-bore diameter variation. Reducing the L/D ratio effectively increases the mass flow rate, velocity, spray angle and reduces the droplet size and breakup length. The increased spray angle results in wall impingements inside the counter-bore cavity, particularly for L/D=1 which can potentially lead to increased deposit accumulation inside fuel injectors. The influences of the counter-bore diameter become more obvious with decreased L/D ratio. For the lower L/D ratio, the sprays with large included angles are more vulnerable to the air entrained into the counter-bore cavity and the recirculation flow inside it. Increasing the counter-bore diameter has an overall adverse effect on the spray characteristics as the spray exits the counter-bore. Flow rates and spray angles decrease and droplet sizes are increased with increased counter-bore diameters for any given L/D ratio. The positive recirculation inside the small diameter counter-bores improves the mass flow rate from the inner hole. Inside the counter-bore cavity and further downstream from it, large interconnected ligaments are present which undergo deformation and secondary breakup.
Numerical Investigation of GDI Injector Nozzle Geometry on Spray Characteristics
Sae Technical Papers
JSAE/SAE 2015 International Powertrains, Fuels & Lubricants Meeting ; 2015
2015-09-01
Aufsatz (Konferenz)
Englisch
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