Non-Intrusive Measurements in Fire Sprinkler Sprays.
Non-Intrusive Measurements in Fire Sprinkler Sprays.
(463 K)
Widmann, J. F.; Sheppard, D. T.; Lueptow, R. M.
Fire Technology, Vol. 37, No. 4, 297-315, 4th Quarter,
October 2001.
Keywords:
sprinklers; sprays; water sprays; drop sizes; velocity
Abstract:
The results of phase Doppler interferometry (PDI) and
particle image velocimetry (PIV) measurements to
characterize the water sprays produced by fire
sprinklers are presented. The large size of the water
drops produced by fire sprinklers, and the relatively
large coverage area of the spray, present significant
challenges when attempting to characterize these sprays.
These difficulties are especially relevant when using
PDI because large drops and large coverage areas may
result in attenuation of the transmitting laser beams.
For the fire sprinkler investigated, it was determined
that attenuation of the laser beam resulted in
over-counting of drops due to burst splitting, a
situation in which the Doppler signals from single drops
are misinterpreted as being due to multiple drops. This
effect was minimized by carefully choosing the operating
conditions of the PDI processing electronics. PIV
measurements provide velocity profiles that can be used
as input for fire dynamics simulations to predict the
effect of sprinkler sprays on fires. The results from
the PIV measurements show good agreement with the
velocity measurements obtained from PDI in the core of
the spray, but poorer agreement along the sprinkler
axis. The discrepancy was attributed to recirculation
zones present in the experimental facility and possible
biasing of the PIV measurements towards the larger
drops.
