Abstract:

In order to address the challenges associated with the long-distance vertical transport of fire suppressant agents delivered by tethered firefighting drones in super high-rise building fires, a vertical transport model for foam extinguishing agents was established. The simulation results were comparatively validated against both empirical model calculations and experimental data. Furthermore, the study conducted an in-depth investigation into the effects of flow rate, gas-liquid ratio, and pipe diameter on pressure loss and flow velocity during the vertical transport of foam extinguishing agents. The findings indicate that the numerical simulation errors remain stable and are consistently less than 3%, demonstrating superior accuracy compared to the empirical model. In terms of flow characteristics, as the flow rate increases, pressure loss gradually rises, with the rate of increase becoming more pronounced at higher flow rates; concurrently, the stabilization time of the flow velocity within the pipe is reduced. Under constant flow rate conditions, when the pipe diameters are 60 mm and 100 mm, respectively, pressure loss decreases with an increase in the gas-liquid ratio. Moreover, increasing the pipe diameter mitigates the influence of the gas-liquid ratio on both frictional pressure drop and flow velocity. The impact of pipe diameter on pressure loss is primarily realized through alterations in the internal flow velocity: as the pipe diameter increases, the flow velocity decreases, leading to a corresponding reduction in frictional pressure drop. Within the pipe diameter range of 40 mm to 60 mm, the effect of pipe diameter on pressure loss and velocity variation is significant; however, when the pipe diameter exceeds 80 mm, this influence gradually diminishes. The research outcomes provide theoretical guidance for the vertical.

Key words: foam fire extinguishing agent, vertical transport, flow characteristic, frictional pressure loss, flow velocity, numerical model