A Deforming Droplet Model for Fuel Spray in Direct-Injection Gasoline Engines 2001-01-1225

A three-dimensional numerical model has been developed to predict spray formation process of swirl or slit type injectors which are currently used in direct-injection gasoline engines. The Discrete Droplet Model (DDM) is totally enhanced: a new droplet deformation model is developed, which is theoretically introduced with a spheroidal shape assumption. The droplet drag model and droplet break-up model via Kelvin-Helmholtz and Rayleigh-Taylor instabilities are modified taken into account with the deformation. The break-up model parameters are dynamically changed according to a droplet Weber number. The model functions are developed using single droplet breakup measurement data. A liquid sheet injection and breakup models are incorporated into the DDM. A new parcel radius model is also introduced to get rid of the grid dependence of the droplet collision-coalescence model.

The present submodels aremore general because there are no special model constants and boundary conditions to be changed according to ambient conditions.

The calculations of swirl and fan sprays are compared with the measurements. The swirl spray angle decreasing under high ambient pressure, which is difficult for conventional models to predict, is simulated very well in the calculations. The good agreement is also obtained for the fan spray formation.