Numerical investigation of blade tip grooving effect on performance and dynamics of an axial flow fan

Appropriate changes to the blade tip structure can effectively improve fan performance. The performance of the OB-84 axial fan with different grooved blade tips is simulated using Fluent. The effects of various tip structures on the flow field, losses distribution, and noise characteristics are investigated. Analysis of static structure and vibration characteristics is performed with the Ansys finite element analysis module. Simulated results show that for the grooved blade tips, both the total pressure rise and shaft power of the fan decrease, but the efficiency improves distinctly; the grooved blade tip structure perturbs the flow and vortex fields and impedes the development of the leakage flow; this eventually results in the reduction of mixing losses between the leakage flow and mainstream. Blade tip case 4 produces the maximum efficiency with an increase of 1.07% at design volume flow rate, and case 7 obtains the lowest shaft power compared with the original tip. Grooved blade tips amplify the fan noise, so measures should be taken to control the noise. Analysis of dynamic characteristics reveals that the distortion and fracture failure of the blade as well as resonance of the impeller would not occur by adopting grooved blade tips.