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Moallemi H, Kharati-Koopaee M. Investigating the Effect of Speed Variation on Performance of a Ducted Single-Stage Axial Flow Fan in the Presence of a Blade Tip-Pattern. Modares Mechanical Engineering 2019; 19 (1) :29-41
URL: http://mme.modares.ac.ir/article-15-18736-en.html

Appropriate changes to the blade tip pattern can effectively improve fan performance. In this research, the effect of two blade tip patterns and speed variation on aerodynamic performance of a ducted axial-flow fan was numerically investigated. In order to ensure the accuracy of the solving method, numerical results were compared with the experimental data from wind tunnel of the NACA Propeller-Research Center. Numerical results show that both the coefficients of pressure and torque increases with the appropriate groove at the tip of the blade. But due to the higher rate of increase in the coefficient of pressure than that of the torque, aerodynamic efficiency has also increased significantly. This increase has been observed in both patterns and in all operational speed of the fan. But, the increase in aerodynamic coefficients had rising trend up to 3000 rpm and, then, declined. The results determine the best pattern for the tip of the blade. In fact, the structure of the groove is such that it traps a rotating airflow with high kinetic energy at the tip, and this vortex, like a barrier, prevents air leakage. This causes reduction in losses due to mixing of the leakage flow and passage flow. With increasing fan rpm, the generated vortexes in tip groov are amplified, which, in addition to a further decrease in the leakage flow rate from the tip region, increases the viscosity and turbulence losses in the area.