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Characterization of a Residential Fire Sprinkler Using Phase Doppler Interferometry.


pdf icon Characterization of a Residential Fire Sprinkler Using Phase Doppler Interferometry. (851 K)
Widmann, J. F.

NISTIR 6561; 36 p. August 2000.

Research and Practice: Bridging the Gap. Fire Suppression and Detection Research Application Symposium. Proceedings. Fire Protection Research Foundation. February 7-9, 2001, Orlando, FL, 703-714 pp, 2001.

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Keywords:

sprinklers; residential buildings; water sprays; uncertainty; residential sprinklers; interferometry

Abstract:

The results of a feasibility study to determine if the water sprays produced by residential fire sprinklers can be accurately characterized using phase Doppler interferometry (PDI) 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 trajectory dependent scattering errors and attenuation of the transmitting laser beams. For the residential sprinkler investigated, it was determined that trajectory ambiguity was not a significant source of error, but attenuation of the laser beam resulted in over-counting of drops due to burst splitting. This effect was minimized by properly choosing the operating conditions of the PDI processing electronics. For the spray investigated, the Sauter mean diameter varied from approximately 360 mum to 560 mum. Integration of the radial profile of the volume flux resulted in a calculated flow rate that agreed with the flow through the sprinkler to within 8%. The results of this study demonstrate that PDI can be used to accurately characterize the sprays produced by residential fire sprinklers.