Abstract
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.
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Abbreviations
- a:
-
Effective passage width
- b:
-
Blade width
- BF :
-
Blockage coefficient due to backflow near the front plate
- BS :
-
Blockage coefficient due to flow separation from suction surface
- Cr, Cu, Cz :
-
Absolute velocity component in radial, circumferential, axial direction, respectively
- Cm :
-
Meridional velocity (nearly equal to Cr at the exit of impeller)
- D:
-
Diameter
- n:
-
Perpendicular direction to flow
- p:
-
Static pressure
- pt :
-
Total pressure
- Q:
-
Volume flow rate
- R:
-
Radius
- Rb :
-
Radius of curvature of blade
- Rv :
-
Radius of scroll (as shown in Figure 1)
- s:
-
Flow direction
- t:
-
Blade thickness
- T:
-
Wake width
- U:
-
Peripheral speed
- w:
-
Relative velocity
- W:
-
Scroll width
- z:
-
Blade number
- α v :
-
Scroll angle
- θ c :
-
Cutoff angle (as shown in Figure 1)
- θ v :
-
Scroll angle from the origin (as shown in Figure 1)
- β:
-
Blade angle
- δ:
-
Opening angle of blade camber at the exit
- ε:
-
Total blockage coefficient
- γ:
-
Flow deflection angle in the discharge stream of blade
- ϕ:
-
Flow coefficient (=Q/πb 2 D 2 U 2)
- μ:
-
Slip factor (=C u2′/C u2)
- ρ:
-
Flow density
- ω:
-
Rotating speed
- ψ:
-
Total pressure coefficient (=Δp t ρU 22 )
- 1, 2:
-
Impeller inlet, outlet or blade tip
- \(\left( - \right)\) :
-
Area-averaged quantity
- \(\left( - \right)\) :
-
Mass-averaged quantity (Prime values denote actual flow angle and velocity with slip considered)
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Guo, EM., Kim, KY. Three-dimensional flow analysis and improvement of slip factor model for forward-curved blades centrifugal fan. KSME International Journal 18, 302–312 (2004). https://doi.org/10.1007/BF03184740
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DOI: https://doi.org/10.1007/BF03184740