Internal Flow Characteristics And Noise Analysis Of Forward Multi-blade Centrifugal Fan

The forward multi-blade centrifugal fan has the characteristics of small size and low noise,which is widely used in the air conditioning system of office and home.In order to meet the requirements of environmental protection,the centrifugal fan needs to develop toward high performance and low noise.The flow inside the multi-blade centrifugal fan is unevenly distributed along the axial direction.The internal flow is really complicated,which is closely related to the aerodynamic performance and acoustic performance of the centrifugal fan.Based on the numerical simulation and experimental research of the airfoil blade multi-blade centrifugal fan,the influence of the variable radius volute tongue on the internal flow field distribution was explored,which is relevant to the aerodynamic performance and acoustic performance of the multi-blade centrifugal fan.(1)Based on the results of steady numerical simulation and experimental tests of the airfoil blade multi-blade centrifugal fan,the feasibility of steady numerical simulation was verified.Three differently arranged variable radius volute tongue of centrifugal fan,Model-A,Model-B and Model-C were investigated by steady numerical simulation.Qualitative and quantitative analysis of flow parameters under rated flow conditions were performed,which included vortex cores in the field,the velocity field,pressure field and vorticity in three different radial sections inside the centrifugal fan,in the light of steady numerical simulation results of four fan models.The research results showed that the variable radius volute tongue centrifugal fans had a great improvement on the flow parameters such as the drop of the inhomogeneity of the velocity field and pressure field,reduction of large vorticity area inside the fan and the vortex core near the volute tongue(2)The transient numerical simulation of the four centrifugal fan models was carried out to investigate the evolution of flow parameters rely on the time in the flow field after the flow was stabilized in the centrifugal fan,which contain velocity field,pressure filed and vortex core of the flow field.The results show that the inhomogeneity of the velocity field and pressure field of the variable radius volute tongue fan models which had been improved were mainly concentrated in the rear part of the flow field of the fan.The vortex core near the volute tongue was significantly reduced.According to the numerical simulation results,the performance of baseline fan and Model-B was experimentally verified.The experimental results indicated that the aerodynamic performance of the Model-B had a significant improvement under rated flow and high flow conditions(3)Based on the results of transient numerical simulation,the noise calculation of four fan models was carried out combined with the acoustic analogy integral module in Fluent.The results revealed that the noise reduction effect of Model-B is obvious.In teams of the numerical simulation results of noise,the noise of baseline fan and Model-B was verified by experiment.The experiment demonstrated that the sound pressure level(SPL)of the Model-B is reduced under all test flow rates conditions,the maximum value of the SPL and the maximum value of the amplitude in the 1/3 octave band spectrum were reduced in the fundamental frequency point in different flow rate conditions.