| Counter-rotating mine fan is widely used as auxiliary fan in coal mine, it is an important part of mine ventilation system. It continuously provides fresh air from adjacent roadway to single tunneling face and discharges toxic gases as well. Facing with growing ventilation demands of long single tunnel during mine excavation, the existing operation mode of counter-rotating fan has a low average operating efficiency, and it is difficult to meet the changing demand of ventilation, then impact working face’s environment. Therefore, with application of variable frequency speed regulating technology in counter-rotating mine fan, researching performance of it with different speed match of the two-stage impellers, would have great significance of improving underground working environment, as the safe and efficient operation of local ventilation in mine.In this paper, domestic and foreign research state of mine fan, the mine ventilation system and underground air standards are analyzed. On the basis of the roadway airflow energy equation and local ventilation theory, the application of counter-rotating fan in heading face’s auxiliary ventilation is studied, and in accordance with the emergency ventilation needs, this project puts forward a new program "diesel-electric hybrid mine safe and fuel-efficient auxiliary fan". 2000 m deep blind alley in high gas mine, for example, the ventilation pipe network characteristic curves are studied when the tunnel depth is 500 m, 1000 m, 1500 m, 2000 m. The analysis found: tunnel of different depth leads to various ventilation resistances, when the depth of roadway is small, the pressure needed is low; with increasing depth, pressure will gradually increasing, when the roadway depth reaches 2000 m, the required pressure could be about 8000 Pa, approaching the fan’s rating pressure. Therefore, in the whole driving process of a deep blind alley, "demand for the wind" may be achieved through adjusting the two-stage impellers’ speed of counter-rotating fan.Counter-rotating fan’s structure and main performance parameters are analyzed in this paper, the force of a single blade and the air flow rate between two stages are analyzed as well. Then set counter-rotating fan noted FBD No8.0 as the researched target, apply the 3D scanning technology for reverse modeling the complex configuration of impellers, and complete the formation of whole model in SolidWorks software. After mesh generation with ICEM CFD and simulation with FLUENT, counter-rotating fan’s main distribution of the flow field in performance and changes of parameters under different conditions are studied when two impellers at 3 kinds of speed match as 2900-2900, 1480-1480, 960-960. The accuracy of this numerical simulation is confirmed by comparing performance parameters and simulation results.According to GB/T1236-2000, the type B(press-in) duct fan aerodynamic performance test bench is set up, and counter-rotating fan’s performance curves under two impellers’ different speed match are given out, here are the conclusions: 1) relationships between flow, pressure and speed obey the similar law of fan, first impeller’s speed is mainly affects the fan flow and pressure depends on the other one; 2) during the early roadway excavation(500m or less), a single-stage operation mode should not be applied, the speed is preferably at 1480-1480; in the range of 500 ~ 1000 m, the speed is preferably at 2000-2000; at the depth of 1000 m or more, the speed is preferably at 2900-2900; and when the depth of excavation is near 2000 m, counter-rotating fan’s operating condition is near the surge, there should be close attention to its operating state to avoid a long running in this condition. Timely adjustment of two-stage impellers’ speed match can achieve underground deep blind alley’s "demand for wind". |
