Influence of hydrodynamic parameters of the jet and geometric parameters of the frame arm and deflector of the sprinkler on foam expansion rate
DOI:
https://doi.org/10.33408/2519-237X.2023.7-2.202Keywords:
automatic extinguishing system, deflector type sprinkler, sprinkler frame arm, sprinkler deflector, nozzle diameter, jet hydrodynamic parameters, Weber number, air-mechanical foam, foam expansion rate, full factorial experimentAbstract
Purpose. To determine the dependence of the expansion rate of air-mechanical foam on the hydrodynamic parameters of the jet of an aqueous solution of a synthetic hydrocarbon foaming agent that does not contain fluorinated surfactants, taking into account the variation in the geometric parameters of the elements of the deflector type sprinkler (nozzle, frame arm and deflector).
Methods. The theoretical methods of analysis, comparison and synthesis, as well as the method of a full factorial experiment to obtain a regression model were used.
Findings. The full factorial experiment on the three levels of five factors affecting the expansion rate of foam generated by the deflector type sprinkler was carried out. The three levels of the Weber number were equal to 23 100, 47 900 and 75 900 accordingly, the frame arm length L was 30, 50 and 150 mm, the deflector working surface coefficient Ks was 50, 64 и 100 %, the outer deflector diameter D was 20, 50 and 100 mm and the deflector taper angle α was 15, 30 and 45°. To generate foam the synthetic hydrocarbon foaming agent Sintek-6NS (6 %), which does not contain fluorinated surfactants and belongs to the foaming agents of general purpose (type S) according to STB 2459-2016, was used. After the analysis of the obtained experimental data the regression model for predicting the foam expansion rate in the studied ranges of values of the Weber number and the geometrical parameters of frame arm and deflector of the sprinkler was developed. For the created model the coefficient of determination R2 is 0.93, which indicates a high accuracy of description of the dependent variable (foam expansion rate K) from the studied factors, while the deviation of theoretical values of foam expansion rate from empirical ones does not exceed 8.9 %.
Application field of research. The developed regression model allows the selection of optimal configurations (combinations of geometric parameters) of the deflector type sprinkler, in particular the deflector working surface coefficient, the outer diameter and the taper angle of the deflector, the frame arm length and the diameter of the sprinkler nozzle to obtain foam with the required expansion rate, depending on the conditions and objectives of the application of the extinguishing agent.
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