Browse Publications Technical Papers 2019-01-0281
2019-04-02

Identification and Characterization of Steady State Spray Conditions in Convergent, Single-Hole Diesel Injectors 2019-01-0281

Reduced-order models typically assume that the flow through the injector orifice is quasi-steady.  The current study investigates to what extent this assumption is true and what factors may induce large-scale variations.  Experimental data were collected from a single-hole metal injector with a smoothly converging hole and a transparent facsimile.  Computations were employed using two engineering-level CFD codes that considered the possibility of cavitation. Gas, likely indicating cavitation, was observed in the nozzles.  Surface roughness was a potential cause for the cavitation.  Neither computational model included these small surface features, and so did not predict internal cavitation.  At steady state, it was found that initial conditions were of little consequence, even if they included bubbles within the sac.  Though the needle was never stationary, the mass discharge by the nozzle remained constant for most of the injection.  The momentum discharge was more sensitive to lower needle lifts than the mass flow rate.  An annular jet, that may follow either the needle surface or the sac wall, forms at low needle lift.  The presence of this jet corresponds to a loss of momentum through the nozzle exit. 

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