Schlieren/Mie-scattering images of a high-volatility fluid impacting on a heated surface:liquid/vapor phase detection

The paper reports the vapor and liquid phase evolutions of sprays impacting on an aluminum flat wall, controlled in temperatures in the range from 300 to 573 K. The fluid is iso-octane, injected at pressures up to 25.0 MPa by a Common Rail apparatus. The spray-wall interaction was characterized by means of high-speed imaging. Schlieren and Mie-scattering images of the sprays were acquired nearly simultaneously along the same line-of-sight. The technique is suitable to highlight fluid with inner density gradients, allowing to detect both the liquid and vapor phase of the evolving spray. The optical system, coupled with a high-speed C-Mos camera, permitted to acquire the evolution of the spray on the wall at a frequency of 25,000 frames/s with images of 640x464 pixels. A customized image-processing procedure was developed was used to batch processing and outlining the contours of the liquid and vapor phase.