Planar dropsizing by elastic and fluorescence scattering in sprays too dense for phase Doppler measurement

An attempt was made to measure, non-intrusively, average droplet sizes in a dense cooling spray of water. The small droplet size and high number density presented severe problems to conventional nonintrusive measurement methodology with phase Doppler anemometry (PDA). A recently developed optical technique, with more promise for measurements in dense sprays, laser sheet dropsizing (LSD), was tried with more success. Sources of error were considered and the uncertainty of the drop sizes measured by LSD was estimated at ±7%, neglecting multiple scattering, dropsize distribution effects and the contributions of droplets at the edge of the laser beam. The greatest of the known contributions to uncertainty is the calibration of the technique against PDA. The greatest of the unknown contributions is likely to be multiple scattering in such dense sprays. Received: 1 March 2000 / Revised version: 25 May 2000 / Published online: 20 September 2000