| Centrifugal fan is widely used in industry and people's livelihood industry because of its large flow coefficient,small size and low noise.Arc blade centrifugal fan,as one of them,is widely used in central air-conditioning industry.With the rapid development of domestic air conditioning industry and the improvement of people's living standard,higher and higher requirements for miniaturization,low noise and high efficiency of fans are put forward.The further study on the aerodynamic and noise characteristics of the curved blade centrifugal fan is helpful to the further development of its industry,the environmental protection and the maximum utilization of resources.This paper takes the arc blade centrifugal fan for central air-conditioning provided by Zhejiang Yilida fan Co.,Ltd.as the research object,and adopts the research method of numerical calculation and experimental verification to study the aerodynamic performance,internal flow characteristics and noise characteristics of the centrifugal fan.The steady calculation of centrifugal fan is based on the Reynolds average(RANS)model,the unsteady calculation is based on the LES model,and the noise calculation is based on the Ffwowcs Williams&Hawkings(F W-H)acoustic analogy model,which is verified by the experiment of Yilida aeroacoustics joint laboratory.(1)The aerodynamic performance and internal flow characteristics of the original centrifugal fan under the condition of small flow rate(Q/Qn=0.03 1)are analyzed.The numerical results show that the unsteady flow occurs in the centrifugal fan,including the vortex at the volute tongue and volute outlet,the vortex shedding at the blade trailing edge,and the separation of the boundary layer near the suction surface of blade.The eddy current has an adverse effect on the aerodynamic performance of centrifugal fan.Secondly,the existence of the volute tongue gap makes the interaction between the flow at the impeller outlet and the volute tongue obvious,which leads to the pressure fluctuation of the local flow at the volute tongue and has a great influence on the noise.(2)In view of the internal flow of the centrifugal fan under the condition of small flow,the influence of variable radius volute tongue on the internal flow and noise results show that the reasonable parameters of volute tongue with variable radius are beneficial to reduce the vortex in volute outlet,blade channel and blade trailing edge,flow loss and gas pressure fluctuation around volute tongue.Under the same rotating speed and design condition,the best predictionperformance is that the static pressure is increased by 10.59 Pa,and the static pressure efficiency is increased by 4.2%.Under the design flow condition,the predicted noise can be reduced by 1.5dB at most(3)In view of the numerical results of the prediction of the variable radius volute tongue structure,the flow and noise characteristics of the centrifugal fan were predicted and verified by experiments with volute tongue structure of different volute tongue clearance ratio.The numerical results show that increasing the ratio of volute clearance can improve the internal flow field of the centrifugal fan,make the internal flow distribution more uniform and the flow loss is reduced;Meanwhile,the experimental results also show that a reasonable ratio of volute tongue clearance can effectively improve the performance fan and reduce the noise of the centrifugal under the same operating conditions.The maximum static pressure of a single centrifugal fan is increased by 7.5Pa,the maximum static pressure efficiency is increased by 3.7%,and the maximum noise reduction is 4dB,the maximum noise reduction of the unit is 3.7dB under the volute tongue clearance ratio of?t/R2=0.12.At the same time,the turbulent noise source is calculated by using large eddy simulation,noise is analyzed by the noise analogy model based on FW-H equation numerical method.This combination is feasible for research on the whole paper. |
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