Experiment And Simulation Study On Flow Resistance Of Superfine Powder Extinguishing Agent In Horizontal Pipelines

Superfine powder has been a new type of halon replacement extinguishing agent because of its excellent fire extinguishing performance and non-pollution for air environment. Currently, the law of superfine powder flow resistance in pipe has been poorly understood, and this limits the design and application of superfine powder extinguishing system greatly.This paper studied the pressure drop variation law of the superfine powder extinguishing agent in horizontal pipelines, and numerically simulated the two-phase flow process of the extinguishing agent. Firstly, by constructing the horizontal discharge test bench and changing the initial filling conditions, the influences of filling pressure and filling ratio on the pressure distribution, the deliver flow and the gas-solid ratio in the pipe were studied, and the appropriate filling conditions were determined. The results indicate that the pressure drop is greatly affected by the initial filling pressure, yet poorly affected by the initial filling mass of the superfine powder. Meanwhile, there are turning points in the curves of the deliver flow with different filling ratios, and the bigger is the initial filling pressure, the bigger is the critical filling ratio value. Furthermore, the pre-discharge step, the stable discharge step and the later discharge step during the discharge process were analyzed through the study of P-t curve. Secondly, the length and diameter of the pipe were changed to explore its influence on the pressure drop. The results show that pressure distribution in the pipe is decreased along the pipe with a linear trend, and the smaller is the pipe diameter, the greater is the pressure drop per meter, the longer is the length of the pipe in the experimental length range, the smaller is the pressure drop per meter. Thirdly, the empirical formula of solid phase friction resistance coefficient in the two-phase flow was determined by dimensionless analysis and multiple linear regression fitting of the experimental data, and the pressure drop calculation formula of the superfine powder extinguishing agent in horizontal pipelines was obtained.Based on Euler two-fluid model, the flow process of extinguishing agent in the pipe was simulated by Fluent6.3, using the3D mesh model built by Gambit. The pressure distribution in pipelines, the velocity distribution and the concentration distribution of the superfine powder were researched. Moreover, the influence of the inlet velocity and the initial solid volume fraction on the pressure drop was also discussed, and the best economic velocities of varieties of flow rate were determined.