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 densi ty presented severe problems to conventional nonintrusive measurement metho dology with phase Doppler anemometry (PDA). A recently developed optical te chnique, with more promise for measurements in dense sprays, laser sheet dr opsizing (LSD), was tried with more success. Sources of error were consider ed 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 t he known contributions to uncertainty is the calibration of the technique a gainst PDA. The greatest of the unknown contributions is likely to be multi ple scattering in such dense sprays.