| Due to the special structure of semi-open axial flow fan in a split-type air conditioner outdoor unit,a series of complicated vortices are formed in the passage,leading to its efficiency and noise index becoming a hot issue of research in recent years.As the crucial component of air duct system in outdoor unit,it is critical for optimized and modified design of the axial flow fan.Therefore,a combination of CFD and genetic algorithm was adopt to optimize the design of a semi-open axial flow fan in air conditioner outdoor unit.The performance before and after the optimization was compared,and the passive flow control method was used to explore the influence of different blade-tip flanging structures on its performance.(1)A simplified three-dimensional model was established,and the appropriate number of mesh was verified by using the mesh independence.The reliability of this numerical calculation method was validated by comparison with the experimental results.Through the analysis of internal flow characteristics,it is found that the tip vortex is dominant in the vortex of the axial fan,which provides a direction for the later optimization and modification.(2)Based on the elementary stage design and composite technology of skew and sweep,the parametric design of a low-pressure axial-flow fan is completed.According to the parameterized description method,the optimized variable range is given,and the flow rate and static pressure efficiency are maximized as the objective.Combined with the improved NSGAII algorithm,an automatic optimization design platform integrating parametric design,mesh generation,flow field calculation,and multi-objective optimization is established.(3)Through numerical simulation,the optimized fan has higher performance including flow rate and static pressure efficiency compared with the original fan.Moreover,the strength of blade tip vortex is smaller,and the flow capacity is stronger.Through aerodynamic performance test,the flow rate and static pressure efficiency increase by 10.4% and 1.7% respectively under design condition.Therefore,this optimization platform has a certain extentof reliability.(4)The effects of different blade-tip flanging structures on the aerodynamic performance,blade tip vortex and entropy generation rate are discussed.Under design conditions,an axial flow fan with a flanging length for 67% of the tip chord length has more flow rate and static pressure efficiency,and has less flow rate attenuation as the pressure increases.On one hand,the blade-tip flanging structures inhibit the formation and development of blade tip vortex,and reduce the entropy generation and flow loss.On the other hand,the structures also increase the friction loss near the wall and enhance the torque of blade. |
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