Numerical Simulation And Experimental Research Of Acoustic Field For Discharge In Blade Tip Of Axial Fan

Axial fan is one kind of fluid machines that is widely used in life and work.The noise problem of axial fan is diffusely regarded in society.Because the turbulent flow will happen due to the interaction of the tip discharge and the main flow during the working of the axial fan.The work performance of the axial fan will be reduced,and the abnormal noise interference will occur.Therefore,it is very important to know the influence of the tip discharge on the pressure field,the fluid field and the acoustic field,also it is very effective for the design and production of the axial fan in low noise and high performance.The flow field of axial fan is simulated based on the JFG axial fan by the FLUENT numerical simulation.According to the cloud figure of the pressure on the surface of the impeller,the maximum static pressure appears at the top of the blade,and it is the main area of working.The total pressure of the leading edge is larger than it in the trailing edge.This result is consistent with the work principle of the axial fan.The static pressure is large while the dynamic pressure is small on the pressure surface,and the distribution of the dynamic pressure is more uniform.This result is in the law of conservation of energy,which also verifies the correctness of the model.According to the figure of the total pressure on the blade,the maximum total pressure is in the tip of the blade,and the dynamic pressure is small on the pressure surface while the total pressure is large on the suction surface.It shows that the flow loss increases due to the vortex caused by the tip discharge and leads to the decrease in the aerodynamic performance.In order to analyse the influence of the tip discharge on aerodynamic noise,the performance curve is acquired through the simulation in different flow rates and different tip sizes.The results show that with the increase of the flow rate,the variation of the power is getting smaller,but the static pressure and the efficiency of the fan decrease with the increase of the flow while the dynamic pressure increases with the flow.In the different tip clearances of 5mm,10 mm,15mm,20 mm,the 10 mm is the most optimal tip clearance,and the efficiency loss of the axial fan is the least in this situation.Then the simulation of the acoustic field is carried based on FLUENT,the maximum sound pressure level appears between 5kHz and 10 kHz,and the level of sound pressure decreases with increasing of the frequency.The maximum value of the sound pressure in the tip monitoring point is larger than the values in other points obviously.The maximum sound pressure in the middle of the blade is smaller than that in the tip monitoring points.The maximum sound pressure in the root monitoring point is the smallest.The correctness of the simulation results of the acoustic field is verified by comparing with the distribution of dynamic pressure on the impeller surface.At last,through the diagram of the sound pressure in time domain concluded in the experiment of the identification of acoustic source in the way of microphone array,the highest response point of the sound pressure level is the point in the tip of the blade.And the level of sound pressure of the sound source signal collected at the two response points located in the middle of the blade is smaller than that in the tip of the blade.The level of sound pressure of the sound source signal in the root of the blade is the lowest.The results of this experiment are also consistent with the conclusions of simulations of the flow field and the acoustic field.