Development of a Spray Model for Low Weber Gasoline Jets in S.I. Engines 982608

Most of liquid jet breakup models now available in combustion codes only apply to high pressure sprays (Diesel … ). When gasoline is injected in the intake pipe of a chamber (S.I. engines), the relative pressure between the injector and the intake gas flow is quite low (3-4 bars). In this case, the spray looks like a long continuous liquid non-evaporating phase. Generally, the jet collapses, giving droplets, far from the tip of the injector. Vaporization is negligible within the pipe. Thus, the assumption generally made that the fuel is gaseous in the chamber fails. The fluid phase can no more be considered fully atomized and dispersed.
We propose here a breakup model for low Weber non-evaporating fuel jets. It takes into account the continuous nature of the spray. The liquid core is represented by cylindrical blobs. The main assumption is that the breakup of a blob is caused by the growth of its surface. A new equation gives the evolution of the surface for each blob. Depending on the Weber number of the jet, this evolution leads either to the atomization or to the breakup of the jet. This gives a more realistic measurement of the liquid core length. In a limit, this model can be applied to higher Weber jets.
This model is implemented in the KIVA-II code and comparisons are carried out with an automotive injector in a quiet atmosphere. Simulations made in a wind channel are also presented. They offer quite similar aerodynamic conditions to those encountered in the intake pipe of a S.I. engine.


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