Optimization Design For Aerodynamic Noise Reduction Of Ultra-high-speed Axial Fan Based On CFD

As a low-cost,high-reliability and high-adaptability cooling and heat dissipation device,axial fans are widely used in electronic appliances,communications and military equipment.However,the inevitable aerodynamic noise during its working time seriously affects the stability of the equipment and the user’s experience.The design of the fan is gradually biased towards the research direction of small size,low noise and high heat dissipation performance.Taking a small military axial fan as the research object,this paper uses a combination of numerical simulation and experimental verification to explore and analyze the flow field and sound field characteristics of the fan.Based on this,single-factor and multi-factor noise reduction methods are used to optimize the design of the prototype fan.The main research contents of this paper are as follows:(1)In order to determine the suitable numerical simulation method for the flow field and sound field of the axial flow fan,this paper establishes the geometric model of the fan then obtains its simulation calculation domain.To determine the simulation boundary conditions and solution settings for turbulence model,dynamic region model and solution algorithm,this paper compares the pros and cons of the two meshing methods,and analyzes the performance of three k-ε turbulence models in the simulation of axial flow fans.The sound field of the fan is simulated by the combination of acoustic analog and CFD.Through the comparison of P-Q performance test and noise test with wind turbine simulation results,the accuracy and reliability of the numerical simulation method are verified.(2)By analyzing the cloud diagrams of physical quantities of the axial flow fan,such as the noise spectrum,static pressure,velocity vector and vorticity,this paper studies the characteristics of its flow field and sound field,and summarizes the flow law in the flow field of the fan.Finally,through the internal flow state of the fan and related acoustic theories,the main location of the aerodynamic sound source is determined.(3)According to the location of the aerodynamic sound source and the mechanism of aerodynamic noise,the effects of single-factor noise reduction methods such as blade installation angle,front bending edge blade and speed on the performance of the fan are studied.Through the comparison of cloud images,the mechanism of related noise reduction methods is explained,which provides a basis for the modification and optimization of axial fans.(4)Based on the single-factor noise reduction method,a multi-factor noise reduction method is proposed,which is reducing the fan speed and increasing the number of blades at the same time.Then,focusing on the impact on the P-Q curve and noise,the changes of the multi-factor noise reduction method on the flow field and sound field characteristics of the fan are studied.Finally,in this paper,the prototype is manufactured and tested under the multi-factor noise reduction method.The test results show that the fan noise has been greatly reduced,which verifies the effectiveness of the proposed method.