PLANAR LASER-INDUCED FLUORESCENCE FOR QUANTIFICATION OF LIQUID REMOVAL AND DEPOSITION DURING SPRAY WALL FILM INTERACTION

In this work, a combination of a spin-coating device and a noninvasive planar laser-induced fluorescence technique is realized for characterization of the interaction of sprays with thin wall films. This system enables investigation of resulting film topography and concentration fields after interaction of binary systems (different liquids for spray and film) in dependency of operating conditions. It can be used for the first time to distinguish between wall film liquid and spray liquid in the residual footprint of the interaction to better understand the underlying physical processes of liquid removal and deposition processes. In this first-time study, the interaction of an automotive spray (ECN Spray-B) with an 8.4 mu m wall film is investigated for atmospheric conditions and different injection pressures and energizing durations. For each case, a complete removal of wall film fluid can be observed in the center of the impingement zone. The wall film liquid is collected in a characteristic rim around the impingement center. With increasing injection pressure, a flattening of the rim and a higher removal rate of wall film liquid is found. This effect is possibly caused by the increased shear acting on the liquid surface or by increased inertia forces due to a stronger impingement of the spray.