The Influence Of Serrated Trailing Edge On The Aerodynamic Performance And Internal Flow Of Axial Fan

Vortex shedding at the trailing edge of the blade is one of the major factors to broadband noise and the loss of the axial fan.The modification of the trailing edge of the blade have the ability to affect the vortex shedding and wake flow,and the trailing edge of the trailing edge is a trailing edge modification method.Studies indicate that it has the potential to reduce the aerodynamic noise of the impeller,but its research on the influence including the trailing edge vortex and wake of the axial fan is still rare.In this paper,an axial fan is used as the object of study,and the sawtooth structure is added at the trailing edge.Combined with the numerical simulation method,the influence of the serrated structure on the aerodynamic characteristics and internal flow of the axial fan is studied.(1)Aerodynamic characteristics of the axial fan are evaluated by the numerical simulation method verified by the experimental results.The results show that the total pressure and efficiency error are less than 5%,which proves the validity of the numerical method.(2)A variety of sine-shaped sawtooth structures were added to the trailing edge of the axial fan.Aerodynamic characteristics of each model were compared and analyzed by numerical simulation.The results show that the sinusoidal sawtooth structure weakens the capacity to generate power of the trailing edge.It improves the efficiency by 1 ~ 2% under the medium and small flow conditions with a reduction of total pressure.The influence of these two parameters on the total pressure and efficiency is different.The aerodynamic performance is more sensitive to the changes in tooth height.(3)Based on the steady and unsteady numerical simulation,the internal flow and dynamic characteristics of the axial fan are analyzed.The results show that the sawtooth structure can cut off the vortex shedding from the trailing edge and reduce the coherence of the vortex at the trailing edge,and lead to the formation of a pair of vortices,which broaden the range of shedding vortex.At the same time,the sawtooth structure effectively weakened the wake strength near the trailing edge of the lower part of the blade,and the inhibition of the wake declined gradually from the bottom of the blade to the middle.The analysis of pressure pulsation indicates that the sawtooth structure can reduce the pulsation amplitude near the trailing edge and mainly low-frequency pressure.(4)The three-dimensional modeling and the structural meshing of impeller blades with the serrated trailing edge are very cumbersome.Parametric modeling of this particular form of impeller blades was carried out.Based on the idea that two-dimensional grid is laminated to construct stereo hexahedral mesh,the structured meshing of the impeller domain was accomplished.Meanwhile,a new way to calculate the weighting factor was proposed,which was verified by grid quality assessment indicators.The results show that the quality of the mesh generated by the transfinite interpolation method was significantly improved.