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Simultaneous Measurements of Drop Size and Velocity in Large-Scale Sprinkler Flows Using Particle Tracking and Laser-Induced Fluorescence.


pdf icon Simultaneous Measurements of Drop Size and Velocity in Large-Scale Sprinkler Flows Using Particle Tracking and Laser-Induced Fluorescence. (6771 K)
Putorti, A. D., Jr.

NIST GCR 04-861; 322 p. February 2004.

Keywords:

sprinklers; drop sizes; lasers; fluorescence; velocity

Abstract:

sprinklers provide an estimated 75% reduction in death rate within residential structures, they are installed in less than 2% of new U.S. homes. A major impediment is sprinkler system cost, which can be reduced by optimization of the water flux distribution to the burning surfaces. If sprinkler drop size and velocity distributions are known, water flux distributions can be predicted. Existing measurement techniques, however, are incapable . of large scale simultaneous measurement of droplet size and velocity, and cannot operate in. fire environments. The Particle Tracking Velocimetry and Imaging (PTVI) technique was developed to provide large-scale, simultaneous, non-intrusive measurement of droplet size and velocity in two phase flows. The apparatus illuminates a 0.5 m by 0.5 m region of the spray field with two consecutive laser sheet pulses of different wavelengths. Dyes in the water fluoresce in two different colors, resulting in two differentiable color images for each drop, which are recorded by a camera. Drop velocity is determined from the distance traveled in the time between the pulses, and size from the areas of the droplet images. Droplet sizes from 200 mum to 3000 mum, and velocities from I m/s to 30 m/s have been measured with low uncertainty. While not studied here, the PTVI technique is general enough to measure many types of two-phase flows, such as those that occur in fire environments, engines, and manufacturing processes.