Pulsed Light-Emitting Diode Photography for Coarse Water Characterization

An optical photography probe employing pulsed light-emitting diode (LED) illumination has been developed for application to coarse water measurement in wet steam. High image resolution (1.38 μm/pixel) and low exposure time (100 ns) photographs capture details of microdynamic flow features with reduced motion blur. Camera and lens are held inside a 50 mm O.D. cylindrical tube, with a custom designed titanium probe head allowing purging air to clear the front optical surface of stagnant liquid. Double exposure images are analyzed using standard image processing techniques to extract the size and velocity of liquid droplets. The accuracy and repeatability of the measurement probe has been verified on air–water sprays with direct comparison to phase-Doppler anemometry (PDA) measurements, which show good agreement.