Full
Outline
In an ultra-high pressure water jet cutting system, the micro jewel nozzle has important influences on the machining efficiency. Cavitation inside the jewel orifice affects the jet formation directly and is a crucial reason for the nozzle wear. By simulating the cavitation flow in the orifice at pressure within 400 MPa, the jet formation process in the nozzle was expounded. The influence of pressure, the aspect ratio and the inlet shape of orifice on the cavitation and jet were also analyzed. At the same time, an experiment was carried out to study the nozzle wear. The results show that the cavitation region in orifice reduces along the nozzle axis with the increasing of the aspect ratio. Moreover, the cavitation region can reach the nozzle outlet when the aspect ratio is smaller than a certain value. At this condition, the jet initial diameter is smaller than the orifice diameter and increases with the increase of pressure. The orifice inlet with a streamline design can effectively restrict the cavitation development. The wear in the jewel orifice inlet due to the cavitation and water erosion is much more severe than in the outlet and is more serious under higher operating pressure. Accordingly, it is useful to select a appropriate aspect ratio for reducing the erosion in the nozzle.
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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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