Effect of blade number on the performance of centrifugal fan

Abstract

The present-day energy crisis challenges the engineers to take careful steps in design of fans. Enhancing the performance of centrifugal fan through parametric analysis is one of the ways. Simulation of centrifugal fan is demonstrated by considering a preliminary design model of backward curved bladed impeller centrifugal having 11 blades (MD1) which is designed using theoretical concepts from fan handbooks to achieve an air capacity of 7 m3/s producing a total pressure at outlet of fan to be 2000 Pa while impeller running at 1500 RPM which is the industrial requirement. Solid model is created and simulation is performed to analyze the fluid flow using Computational Fluid Dynamics (CFD). Results of this preliminary model show that a total pressure of 1323.07 Pa at the outlet of fan is achieved with an efficiency of 50.82%. Need for improvement in performance and to the study of effect of blade number on the model has led to perform simulations by varying the number of blades of impeller to Z = 8, 10, 12, 14 while keeping all the parameters identical to the design point condition. Contour plots of flow and velocity vectors in the blade passages areas for different cases along with the total pressure and efficiency are compared. Assessment of these results shows that when blade number Z = 14, there is an increase in total pressure by 21.77% and efficiency by 5.74% in comparison with design point condition. The centrifugal fan is simulated successfully as the residuals shows good convergence of <10−5.