Visualization and Analysis of Spray Impingement Under Cross-Flow Conditions 2002-01-2664

Gasoline Direct Injection (GDI) engines are becoming increasingly popular due to the potential to improve power and fuel consumption. The direct injection of gasoline inside an engine is classified in three types: wall-guided; air-guided; and spray-guided (also designated as air-assisted). In the wall-guided, spray impingement on the piston's bowl head is part of the process to form a stratified charge near the spark plug, as well as to aid in the fuel mixture preparation. In the air-guided (swirl and tumble) and spray-guided, the impingement is undesirable.

The interaction between the spray and the surrounding air, as well as the characteristics of the spray, are very important to achieve the benefits of the GDI concept. Although many works have been published which consider the structure of individual sprays, much remains to be known about the interaction between the spray and the wall in the presence of air motion. This is the goal of our work. For that an experimental facility has been built to study the fluid and thermodynamic behavior of a gasoline spray impinging onto a cold/heated surface under cross flow conditions. In a first step of our study we intend to build a fundamental basis on the influence of droplet size and velocity relatively to the cross flow and, therefore, used a PFI injector for easy of experimental analysis. Despite this injector operates at low pressure, images of the spray under quiescent conditions showed a spray quality similar to that of a DI injector, without injection of streams of liquid. Also, measurements obtained with a phase Doppler anemometer showed that droplet sizes range between 10μm and 120μm.

The present paper reports the results obtained with Mie scattering and shadowgraph using a high speed CCD camera to analyze the influence of the pressure and duration of injection in the spray/wall interaction, considering the presence of different cross flow velocities.