To address the efficiency reduction caused by clearance backflow at the volute tongue of a double‑suction multi‑wing centrifugal fan,a clearance adjustment control structure unit is proposed.This unit is installed on the front and rear cover plates of the volute near the volute tongue to achieve clearance adjustment.By adding structural units of different thicknesses to adjust the clearance,numerical analysis methods are used to simulate the internal flow field of the fan under different clearances.The effectiveness of the clearance adjustment is verified through aerodynamic performance and noise tests of the fan.The results show that the clearance adjustment unit can effectively reduce backflow at the volute tongue,improve the static pressure recovery capability of the volute,and ameliorate the backflow state at the impeller front shroud.It also enhances the axial distribution uniformity of the annular flow rate at the impeller outlet,thereby increasing the impeller work efficiency.However,when the axial thickness of clearance adjustment unit is excessive,it aggravates impact at the volute tongue,leading to a noise increase of 4.8 dB.When the axial thicknesses of the two clearance adjustment units are equal to the axial distances between the impeller front and rear shrouds and the volute front and rear cover plates,respectively,the measured noise can be reduced by 0.7 dB,the maximum air volume increased by 0.8 m3/min,and the efficiency improved by nearly 2%.This study provides a theoretical basis and engineering practice reference for the aerodynamic performance optimization and low‑noise design of multi‑wing centrifugal fans.
| 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 |