Study On The Internal Flow Field Of The Mine Counter-rotating Axial Fan

Counter-rotating axial flow fans are widely used in mine and metallurgical engineering,petroleum and chemical engineering,traffic tunnel engineering,and many other kinds of industrial and engineering because of some advantages,such as easily installation and use,easily inverted ventilation,broad and stable scope of work.The efficiency increase of the counter-rotating axial flow fans will inevitably bring in great economic benefits and social benefits.With the improvement of computational fluid dynamics and the development of the computational technology,numerical simulation has been widely applied to study the counter-rotating axial flow fan.Based on the overall scheme design of the counter-rotating axial flow fan,threedimensional geometric model of the whole flow field has been built,including the collector,installation section of the first stage motor,the first stage moving impeller,the second stage moving impeller,installation section of the second stage motor and the diffuser.The computational domain has been generated with the structured hexahedron grid elements,the grid dense distribution is reasonable according to the geometric model.The RNG k-? turbulence model has been used to close the governing equations,and the SIMPLE algorithm has been used to realize the coupling of velocity and pressure to accomplish governing equations.The moving reference frame model has been used to the steady simulation,and the moving mesh model has been used to the unsteady simulation.Three different axial spacing size models and three different radial clearance size models have been studied.According to the steady and unsteady simulation results,regularities of distribution of some parameters,such as velocity,pressure,pressure variation and acoustic power have been acquired.According to the comparison between different simulations,we can see that:(1)The bigger axial spacing size(0.4x leaf chord)is propitious to eliminate the mutual influence between the first and second stage moving impeller,to uniform intake air for the second stage moving impeller,to increase the flow of the fan,to reduce fan noise.The axial spacing size has small influence to the pressure rise of the fan.(2)The pressure variation of the inlet and installation section of the first stage motor is weak,the negative pressure value is bigger with the increase of the axial spacing size,and is propitious to increase the flow of the fan.The pressure variation of the first and second stage moving impeller is the biggest,and the pressure transits from the negative pressure to the positive pressure in the flow direction of the air flow.The positive pressure value of the pressure variation is bigger with the increase of the axial spacing size.(3)The smaller radial clearance size(0.008 x leaf diameter)is propitious to increase the pressure rise of the fan,and has a negative impact to the flowof the fan because of the small flow area.Meanwhile,the small radial clearance size also has a negative impact to the aerodynamic noise.(4)The range value of the pressure variation is bigger with the decrease of the radial clearance size.The smaller of the radial clearance size,the bigger of the positive pressure value and the pressure rise.54 figures,3 tables and 96 references are included in the dissertation.