Wavelet analysis was performed for the collected pressure signals of gas-liquid two-phase flow in a vertical pipe in an air lift test. The optimal wavelet basis functions were determined by improving the signal-to-noise ratio (SNR). The range of decomposition levels was determined based on changes in energy of detail coefficients, and optimal decomposition levels were determined by the entropy weight method together with SNR, root mean square error and smoothness. After denoise with wavelet thresholding, three-level decomposition of signal was performed with the wavelet packet method, and then flow patterns were identified for gas-liquid two-phase flow with the energy ratio in the 1st and 2nd frequency bands and entropy values as feature vectors. The flow pattern recognition based on 389 sets of pressure signals shows that the extraction feature vector combined with random subspace decision tree can efficiently identify and classify gas-liquid two-phase flow patterns, and the overall mean recognition rate is up to 98.08% by adopting the improved wavelet thresholding.
| 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 |