| The contra-rotating local fans used in mines are important equipment for ventilation and ventilation in underground local areas such as rock roadway and coal road way heading face,but its high noise causes serious pollution to the limited space of the working face,which not only deteriorates the working environment of the workers,but also interferes with the signal of the underground.Therefore,how to further improve the acoustic performance and reduce the operating noise of the local ventilator under the premise of ensuring that the aerodynamic performance of the local fan is not significantly reduced is of great significance for improving the underground working environment and ensuring the safety of production.In this thesis,three kinds of blade biomimetic structures are designed for the front stage rotor of a mine counter-rotating local fan.On the basis of the large eddy simulation(LES)method and the FW-H equation,the influence of the two kinds of blade bionic noise reduction measures on the aerodynamic and acoustic performance of the local fan is analyzed.The main research work includes the following aspects:(1)Firstly,under the design condition flow rate(Qd),the influence of three bionic blade structures on the aerodynamic performance of local fan is studied respectively.Compared with the original blade,the three bionic blade structures were adopted,such as serrated trailing-edge,wavy leading-edge,serrated trailing-edge and wavy leading-edge.The total pressure rise of the fan decreased by 6.66%,1.21%and 6.18%,and the total pressure efficiency decreased by 0.21%,0.61%and 0.86%,respectively.The decrease range is not significant.Then the influence of three bionic blade structures on the aerodynamic performance of local fan under different flow conditions is analyzed numerically.At low flow rate(0.8Qd),the effect of three kinds of bionic blade structures on the total pressure efficiency and the total pressure rise of the local fan is relatively small At high flow rate(1.2Qd),the total pressure rise and total pressure efficiency of the fan can be improved significantly by using the wavy leading-edge bionic blade,while the total pressure efficiency and total pressure rise of the fan can be greatly reduced by using the serrated trailing-edge,serrated trailing-edge and wavy leading-edge bionic blade structure Therefore,in order to ensure that the bionic blade structure does not significantly reduce the aerodynamic performance of the local fan,the fan should be operated as far as possible under the design flow conditions and slightly less than the design flow conditions.(2)Based on LES method and combined with numerical analysis of FW-H equation,the noise reduction mechanism of the serrated trailing-edge and wavy leading-edge bionic blade structures on the discrete tonal noise and the turbulent broadband noise of the fan is revealed.It is found that the large-scale spreading vortex shedding at the trailing-edge of the original blade(straight trailing-edge)is suppressed,and the pressure pulsation intensity of the blade surface is weakened,thus the discrete tonal noise is reduced.The wavy leading-edge structure bionic blade can significantly reduce the pressure pulsation at the leading-edge of the front blades,thus reducing the turbulence broadband noise of the fan.(3)The performance of three kinds of bionic blade structures,such as serrated trailing-edge,wavy leading-edge,serrated trailing-edge and wavy leading-edge was compared and analyzed by numerical simulation.The results show that compared with the original blade structures,the three bionic blade structures investigated in this paper have a certain noise reduction effect without significantly reducing the aerodynamic performance of the local fan.the discrete tonal noise of the fan can be reduced by 2.2 dB、3.8 dB and 5 dB,respectively,and the turbulent broadband noise can be reduced by more than 10 dB. |
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