Discharge Distribution Performance for an Axisymmetric Model of a Fire Sprinkler Head

摘要

A nondimensional description of spray discharge distribution performance of fire sprinkler heads is developed. The description emphasizes the sprinkler's ability to evenly distribute the spray over the maximum possible floor area. Illustration of the description is provided by data obtained from an apparatus developed to study the axisymmetric jet impingement on a flat disk. The apparatus employs the disintegration of an axisymmetric film to produce the droplet spray. Sheet breakup radius varies as the inverse one third power of the Weber number based on jet diameter, in agreement with data obtained by Huang. Variable discharge distribution performance is achieved by controlled axial vibrations of the disk. Identical nondimensional distributions are obtained at a frequency ratio defined as the ratio of the driving frequency to the frequency of maximum growth of sinuous waves, as outlined by Squire. A spray modelling procedure is developed to give analytical discharge distributions. An investigation of the resulting patterns indicates a volume mean droplet diameter in agreement with a predicted value obtained from a correlation given by Dundas and Huang.