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In order to optimize engineering fire-extinguishing technologies, numerical simulation was employed to investigate the effects of flow rate and pipe diameter at the foam inlet on the transport behavior of compressed air foam. In the simulation, the flow rate varied within the range of 1 000-2 400 L/min, and the pipe diameter ranged from DN80 to DN220. Characteristic parameters characterizing foam transport were extracted, including flow field, vorticity, viscosity, and pressure drop. The results show that the velocity of the foam fluid at the elbow forms three regions from the outside to the inside: low-speed, high-speed, and low-speed. However, the flow rate and pipe diameter changes have different degrees of influence on these three regions. Regarding the effect of inlet flow rate, there is a positive correlation between vorticity and inlet flow rate. Additionally, the low-speed region on the inner side of the elbow increases, the high-speed region is squeezed toward the outer wall, and the range of the low-speed region on the outer side decreases. Meanwhile, as the inlet flow rate of the foam fluid increases, the viscosity of the fluid gradually decreases, and the pressure drop first increases and then tends to stabilize. In terms of the influence of pipe diameter, compared with the inlet flow rate, the changes in velocity stratification and vortex near the elbow are relatively slight when the pipe diameter increases. Moreover, the pressure drop inside the pipe gradually decreases with the increase in pipe diameter. When the pipe diameter increases from DN80 to DN220, the local pressure drops decreases by approximately two-thirds.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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