This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.

Three-dimensional flow analysis and improvement of slip factor model for forward-curved blades centrifugal fan

A sirocco fan is a centrifugal fan with a forward curved blade. It is used for low pressure but has a large discharge use. In this paper, at first, nine impellers with various blade shapes were tested in the same casing. The measurements of the three-dimensional time variant velocity at the outlet of the impeller were done using four impellers having better
performances among them. The relations between fan performance and outlet velocity were considered. The effects of the blade shape on the performance were considered.
The blade inlet and outlet angles and blade inclination angles which have the best performance were considered. The design parameters of designing a sirocco fan impeller was described.

/pdf/study-on-the-performance-of-a-sirocco-fan-optimum-design-of-2wt7hnxf93.pdf

Study on the Performance of a Sirocco Fan (Optimum Design of Blade Shape)

In this study, the unique reverse-flow around the inlet nozzle of a squirrel-cage fan was numerically studied by computational fluid dynamics (CFD), and a non-axisymmetric D-type inlet nozzle was p...

https://www.tandfonline.com/doi/pdf/10.1080/19942060.2021.1883115

Numerical and experimental investigations on non-axisymmetric D-type inlet nozzle for a squirrel-cage fan

The flow at the exit from the runner blade of a centrifugal fan with forward curved blades (a sirocco fan) sometimes separates and becomes unstable. We have conducted many researches on the impeller shape of a sirocco fan, proper inlet and exit blade angles were considered to obtain optimum performance. In this paper, the casing shape were decided by changing the circumferential angle, magnifying angle and the width, 21 sorts of casings were used. Performance tests, inner flow velocity and pressure distributions were measured as well. Computational fluid dynamic calculations were also made and compared with the experimental results. Finally, the most suitable casing shape for best performance is considered.

Study on the effects of flow in the volute casing on the performance of a sirocco fan

A literature review on the squirrel-cage fans using in HVAC equipment: Powerful, efficient, and quiet operation

In this paper, prediction of the shaft power is studied. The slip factor and the leakage flow factor used for the performance calculation are obtained experimentaly. The method of prediction of the shaft power is based on the angular momentum theory, and it is derived from measurement of the slip factor, blockage factor and leakage flow. The slip factor is strongly related to the blade angle β2, the number of blades Z and the capacity coefficient φ, and it is smaller than 0.35 at 170 degree of β2, which is much smaller than that for the backward blades. The difference between the calculated values and the experimental results on the shaft power is 5 % for the range of φ less than 0.3 and is 11 % for φ= 0.45.

Susumu Yamazaki

Papers

多翼送風機の空力性能に関する研究 : 第2報,軸動力の予測計算に関する研究