Experimental and Numerical Characterization of Gasoline-Ethanol Blends from a GDI Multi-Hole Injector by Means of Multi-Component Approach

This paper reports an experimental and numerical investigation of the spray structure development for pure gasoline fuel and two different ethanol-gasoline blends (10% and 85% ethanol). A numerical methodology has been developed to improve the prediction of the pure and blends fuel spray. The fuel sprays have been simulated by means of a 3D-CFD code, adopting a multi-component approach for the fuel simulations. The vaporization behavior of the real fuel has been improved testing blends of 7 hydrocarbons and a reduced multi-component model has been defined in order to reduce the computational cost of the CFD simulations. Particular care has been also dedicated to the modeling of the atomization and secondary breakup processes occurring to the GDI sprays. The multi-hole jets have been simulated by means of a new atomization approach combined with the Kelvin-Helmholtz/Rayleigh-Taylor hybrid model. At the nozzle hole exit an initial distribution of atomized droplets has been predicted by the numerical approach taking into account cavitation phenomena and turbulent effects. Sprays have been investigated using a 6-hole gasoline direct-injection (GDI) injector and injecting fuel into an optically-accessible constant volume vessel at 5.0, 10.0, and 15.0 MPa of injection pressure, at ambient back pressure. Mie-scattering images have been performed using a high-speed camera and a pulsed-wave flash system which is able to track liquid phase in order to estimate the spray development, morphology and cone angle. Moreover fuel injection rates measurements have been carried out using a meter working on the Bosch tube principle to characterize the injected mass. The liquid fuel penetration registered highest values for gasoline fuel with respect to its blends with ethanol at different percentages.