Effect of Blade Slot Inclination Angle on Flow Separation in The Centrifugal Fan Impeller

Beskales, Samer Anwer; Shahin, Ibrahim Mahmoud; Ayad, Samir Sobhy; Abdellatif, Osama Ezzat; Mekhail, Tarek

doi:10.21608/erjsh.2023.213922.1177

	Effect of Blade Slot Inclination Angle on Flow Separation in The Centrifugal Fan Impeller
Engineering Research Journal (Shoubra)
Volume 52, Issue 4, October 2023, Page 193-203 PDF (2.13 MB)
Document Type: Research articles
DOI: 10.21608/erjsh.2023.213922.1177
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Authors
Samer Anwer Beskales ¹; Ibrahim Mahmoud Shahin¹; Samir Sobhy Ayad¹; Osama Ezzat Abdellatif¹; Tarek Mekhail²
¹Department of Mechanical Engineering, Faculty of Engineering at Shoubra, Benha University, Shoubra, Cairo, Egypt.
²Department of Mechanical Engineering, Faculty of Energy Engineering- Aswan University, Aswan, Egypt
Abstract
The use of slotted blades for centrifugal fan impellers improves fluid flow steadiness and reduces fan noise. The slots create a jet of fluid from the pressure side to the suction side that increases the momentum of the main flow and postpones the flow separation. In addition, these slots make the fluid movement smoother and more efficient in impeller passages. In previous research, the optimum slot location was determined at 40% from the leading edge (at diameter Ds=0.65 DImpeller) with a 2.5 mm width. The present research concentrates on determining the optimum slot jet angle of a ten-blade backward curved centrifugal fan at the best efficiency point (BEP). Six values of slot inclination angles, namely θS1, θS2, θS3, θS4, θS5 and θS6, ranging from an inward slot direction of (+60°) to an outward direction of (-80°), are tested numerically using an unsteady Computational Fluid Dynamics (CFD) model. The CFD visualization results have proven the benefits of the outward slots that ranged from (θS= -60° to -80°) on stall control of the fluid on the blade suction side compared with the inward slots. At the BEP, the computed performance of the tested fan with an outward slot inclination angle θS6 =-80° showed a 2.6 percent efficiency improvement compared to fans with an inward slot of θS1 =+60°. Generally, the outward slot direction has a positive effect on the boundary layer attachment on the suction side of the blade.
Keywords
Suction slots; slot inclination angle; Fan performance; CFD; Slotted blade


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