A modeling basis for predicting the initial sprinkler spray

The performance of water-based fire suppression systems is governed by the dispersion of the water drops in the spray. Characterization of the spray is essential for predicting and evaluating the performance of these suppression systems. The dispersion of the spray is typically modeled using particle tracking methods. The accuracy of the spray characterization using this approach is quite sensitive to the initial spray specification. A physics-based atomization model has been developed for prediction of the initial spray. Inputs to this model include injector geometry, injection pressure, ambient environment, and suppressant fluid properties. This atomization model also accounts for the stochastic behavior of the physical processes governing spray formation and provides probability distributions of initial drop sizes and locations for the initial spray. This modeling approach can be integrated with drop dispersion models and CFD models to characterize spray dispersion in quiescent environments or evaluate suppression performance in fire environments. The drop size predictions using the proposed atomization model have demonstrated favorable agreement with actual sprinkler spray measurements over a range of operating conditions.