Simultaneous Measurements of Drop Size and Velocity in Large-Scale Sprinkler Flows Using Particle Tracking and Laser-Induced Fluorescence.
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899