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| Comparative analysis of three types of straightener in long range firefighting water cannon |
| Xiang Qingjiang, Shi Zhefu, Li Hong, Chen Chao |
| National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China |
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Abstract Three types of straightener are designed which have approximately the same cross section area. In the two cases where the straighteners take up the same volume and surface area as the flow passage, the numerical simulations of flow in the water cannon are studied at 1 500 m3/h design flow rate. The results show that the flow pattern is improved evidently when the straighteners are installed, and the axial velocity near the outlet increases more greatly than the case without straightener. The total hydraulic loss is ranged from 0.10 to 0.13 MPa, and its 55% occurs across the straightener. Although the bullet-shaped straightener(shape Ⅲ)has the smallest total hydraulic loss, the rectifying effect is poorer than the double-circle section straightener(shape Ⅰ)and the multi-rectangular section straightener(shape Ⅱ). Moreover, the bullet-shaped straightener has a streamlined inlet structure, causing a less dynamic pressure loss. The surface area of straightener exhibits a more significant rectifying effect than the volume does. The maximum average turbulent kinetic energy is found at the outlet of water cannon without straightener. The energy declines once a straightener is installed. However, there is a suitable length for a straightener, once this length is selected, the position of straightener in cannon tube has little influence on the rectifying effect.
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Received: 03 September 2014
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