High speed imaging of fuel sprays using a low-cost illumination source

Abstract

The recent availability of (affordable) high frame rate electronic imaging with large frame counts now allows for parametric, time-resolved investigations of the liquid break-up processes that dominate the atomization. In previous investigations high-speed background shadowgraphy was used to observe the liquid sheet breakup process downstream of prefilming airblast atomizers. Here the choice of illumination was one of the challenges and ultimately employed a high-power continuous light source. A careful trade-off between sufficient camera exposure time and tolerable motion blur yielded images of adequate contrast to successfully complete the investigation. As an alternative to high power continuous light sources the article explores the use pulsed light illumination for imaging applications of this type. In particular recent efforts utilizing pulsed light-emitting diodes (LEDs) are described. Images acquired in an in-line illumination arrangement exhibit high contrast and practical absence of frame-to-frame intensity fluctuations, and thus are well suited for statistical and time-spectral image processing.