Detailed Modeling of Liquid Fuel Sprays in One-Dimensional Gas Flow Simulation 2004-01-3000

In internal combustion engines, liquid fuel injection is one of the most prevalent means of fuel delivery and air-fuel mixture preparation. The behavior of the fuel spray and wall film is a key factor in determining air-fuel mixing and hence combustion and emissions.

A comprehensive model for the liquid fuel spray has been developed in conjunction with the one-dimensional gas flow code WAVE. The model includes droplet dynamics and evaporation, spray-wall impingement, wall film dynamics and evaporation. The fuel injector can be placed in the manifold, inlet port or cylinder. Liquid fuel droplets are injected with a prescribed size distribution, and their subsequent movement and vaporization are modeled via the discrete particle approach, frequently used in multi-dimensional CFD codes. This approach ensures conservation of mass, momentum and energy between the gas and liquid phases. The code takes account of impingement on the port wall and various obstacle surfaces such as the back face of the valve. It predicts the impingement outcomes from the incidence angle and the impingement site, and the fuel film formation, motion and evaporation. The code also simulates the fuel film stripping off on a sharp edge and as droplets re-entering the gas flow, and includes the model of droplets ejection due to the film squeezed by a descending valve.

The model has been tested and validated with measurements, including the single droplet evaporation, spray tip penetration and engine transient operations. The model is easy to use, and the predictions are satisfactory, comparing with the measurements.