Abstract
In the marine fire suppression system, continuous delivery of dry chemical powder to the fire source with long powder discharge range and high dispersion concentration is essential. The work is devoted to experimental and numerical studies of the flow characteristics of the dry chemical powder jet from a horizontal injector with a wide range of Stokes numbers between 6 to 30 and Reynolds numbers between 4792 to 23,960 by considering the effect of gravitational acceleration. A CFD-based Eulerian–Eulerian multiphase model combined with Standard k-ω turbulence model was used to predict flow characteristics of particle-laden jet using dimensionless numbers, including the solid volume fraction, the normalized velocity magnitude, and the turbulent viscosity ratio. Experimental studies have been carried out for three different inflow velocities (2.06, 2.45, and 2.81 m/s). The results indicate that the particle density plays a significant role in the dispersion of the particles in the radial and axial directions. The transition from U-shaped to V-shaped solid dispersion structure on the ground can be captured with the increase of particle density. Moreover, the higher level turbulence intensity enhances the solid dispersion concentration. Finally, it was found that the Portland cement powder exhibits better discharge performance in terms of solid discharge range and dispersion concentration in comparison with other dry powders. These results have implications in the design of powder-based fire suppression system. Further studies should aim to the in-depth research on the fire extinguishing mechanism of the Portland cement powder, especially the fire suppression effectiveness and thermal decomposition process.
Highlights
Two-phase particle-laden turbulent jets have been utilized in a broad range of scientific and engineering applications, such as the mining process, pneumatic transport, particulate pollution control, fluidized bed mixing, and fire suppression process in marine industry
The Reynolds number Re is the ratio of inertial forces to viscous forces, and the Stokes number St expresses the relationship between the particle relaxation time and the fluid characteristic time
D is the diameter of the injector, Dp is the diameter of particle, Uin is the inlet flow velocity, and μ is the viscosity of air
Summary
Two-phase particle-laden turbulent jets have been utilized in a broad range of scientific and engineering applications, such as the mining process, pneumatic transport, particulate pollution control, fluidized bed mixing, and fire suppression process in marine industry. Among these involved applications, discharging powders from a injector is often encountered, especially in the fire suppression in a ship under sea condition. In the fire exhausting process, many fire-extinguishing agents (e.g., water, foam, CO2, dry chemical powder) and equipment (e.g., sprinkler, fire hose nozzle) have been investigated and adopted in a wide range of fire protection fields. Improving the efficiency of the powder injector, thereby enhancing the fire suppressing performance of dry powders, has become the main object in the marine fire suppression field
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