Numerical Simulation And Comparison Of Inner-flow Field For Centrifugal Fans

Centrifugal fans are widely used in aeronautics, power and energy, chemical engineering, metallurgy and many other industries, while the impeller is one of the most impotent parts of the centriful fans. The quality of the impeller can give much influence to the inner-flow field of the centrifugal fans. In the engineering, the impeller blade is designed by twist ruled surface which can not be milled accurately by cylindrical cutter or by taper cutter. Flank milling twist ruled surfaces is the widely used method, but the errors can not be avoided. This paper just care about what influence will be brought by the milling errors.Based on the CAD software UG, the models of centrifugal fans with ruled-surface impeller versus with enveloping surface impeller are developed. Both of the models are composed of three parts: the entrance part, the central part and the scroll case. The pars of the two models are absolutely the same except the central parts for they have different impellers. And two models of single channel are also developed, one is formed by ruled-surface impeller, and the other is formed by enveloping surface impeller.The mesh of the two models of centrifugal fans and the two models of single channel is developed by the professional software Gambit, and then the boundary conditions are fixed on. The boundary condions of the two models of centrifugal fans are the same, and those of the two models of single channel are the same too.By using the CFD software FLUENT, the inner-flow field of centrifugal fans with ruled-surface impeller versus with enveloping surface impeller has been simulated. The static pressure distribution, the dynamic pressure distribution, the total pressure distribution, the turbulent intensity and the speed vector of the two kinds of centrifugal fans are then analyzed and compared. From the calculating results, we found that the pressure distribution, the speed vector and other parameters of the two kinds of centrifugal fans are basically same. This implies that the tool-path generating arithmetic for the machining of the impeller can meet the aerodynamic requirements of the centrifugal fan. Furthermore the method can provide proof for designing department to establish sound manufacturing tolerance for impeller.