| With the increase of mining depth and the ventilation resistance,the existing type of local counter-rotating fan can't run efficiently and steadily under the design condition for a long time.When the fan is in a off-design condition for a long time,it will not only cause the waste of electric energy due to low efficiency,but also affect the safety of underground production.Therefore,a new type of blade adjustable fan was designed and its performance characteristics are studied.It is of great significance to the efficient and rational operation of the fan under the changing ventilation condition.First,the design scheme of single motor external adjustable counter-rotating fan is proposed,which combines the external spin drive with the single motor and the self generating blade angle adjusting device based on the photoelectric control.The dynamic analysis of the regulating mechanism is carried out by using ADAMS.The adjustment range of the blade angle of the adjusting mechanism is 0°~27°.The speed fluctuation in the regulation process is controlled within 4.52% of the minimum speed,which verifies the stability of the regulating mechanism and the rationality of the power source.Combined with Workbench,modal analysis of impeller after installation of regulating mechanism is carried out.It is found that the governing mechanism is stable in the hub,and the natural frequencies of each stage avoid the working frequency of the fan,which verifies the safety of the regulating mechanism.In order to study the influence of the structural parameters of the single motor external drive on the performance of the fan,the CFD software is used to compare the performance and internal flow conditions of the single motor external counter-rotating fan and the dual motor built in FBD No8.0 2 x 55 kW fan,and verify the correctness of the simulation through the test.The results show that: The change of the structural parameters of the single motor external counter-rotating fan has a certain influence on the airflow stability in the fan,but the overall performance of the fan is good,and the performance of the single motor external fan under the different impeller speeds is better than the FBD No8.0 2×55kW fan.With the decrease of flow rate,the difference of total pressure and efficiency between two fans increased.With the increase of speed,the difference of total pressure between two fans increased,and the difference of efficiency value decreased.In addition,in order to study the influence of rotor blade regulation and frequency regulation on the performance of a single motor external adjustable counter-rotating fan,through numerical simulation,under the designed flow,the performance of fans is compared and analyzed for three situations,which are matching of different front blade angles and two and speed,different matching angles of rear stage blades and two and speed,and two stage blades of design flow at the same time.In the end,based on the results of numerical simulation,resistance of tunnel pipe network with depth of 500 m and 1500 m as the representative of long and short distance ventilation,the influence of three factors,such as blade number,blade angle and impeller speed,on various performance indexes of fan is investigated by orthogonal test.Research shows that no matter which kind of roadway depth is,the influence of changing the speed of two stage impeller to the flow,pressure and shaft power of the fan is always the greatest.The second is the single stage blade installation angle,and the number of single blade is the smallest.The effect of changing the two stage speed on fan efficiency is the lowest among all factors.The change of installation angle of single stage blade has the most significant effect on efficiency of fan.In addition,based on the results of orthogonal test,the collocation of the factors with the highest fan efficiency was selected under the 500 m and 1500 m depth of the tunnel environment. |
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