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Outline
In order to study the internal flow field and induced pressure pulsation phenomena at the inception of cavitation and to determine a reasonable critical cavitation criterion, this paper conducted cavitation experiment on a low specific speed centrifugal pump and carried out steady and unsteady CFD simulations based on the RNG k- ε turbulence model and Rayleigh-Plesset cavitation model. The errors of efficiency and head are within 3%. Energy performance, flow field, and pulsation analyses were conducted under both non-cavitating conditions and different degrees of cavitation. The results indicate that the overall flow state is stable, and that the transport and collapse of local bubbles cause turbulent dissipation, leading to low-frequency pressure pulsation when cavitation triggers a 1% efficiency drop. When the head drops by 3%, the flow state in the pump is disturbed with vortex and large energy loss, and the wide band pressure pulsation which is easy to cause the vibration and noise of the pump body is induced. In the design of low-specific-speed centrifugal pump, it is recommended to set the critical cavitation margin to the device cavitation margin and above when the efficiency is reduced by 1% to ensure the stable operation of the pump. The research results can provide reference for the optimization design of low specific speed centrifugal pumps.
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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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