Effects of Sweep, Dihedral and Skew on Aerodynamic Performance of Low-Pressure Axial Fans With Small Hub-to-Tip Diameter Ratio

Wang, Jie; Kruyt, Nicolaas P.

doi:10.1115/1.4051542

Cited by 8 publications

(10 citation statements)

References 25 publications

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“…[83,90] and the streamlines from CFD simulations in Refs. [89,91,93] near the blade suction side surface also confirmed this. Therefore, the accumulation of low-momentum fluid near the tip is reduced.…”

Section: Sweep Dihedral and Skewsupporting

confidence: 67%

“…It should be noted that the stagger angle χ(r ) in the current study is measured relative to the axial direction (contrary to the the stagger angle defined in Refs. [50,93] where the circumferential direction has been used as reference).…”

Section: Vortex Distribution Design Methodsmentioning

confidence: 99%

“…The results reported in this chapter are adapted from the published paper [93]. The research background is introduced in Sec.…”

Section: Effect Of Blade Skew On Aerodynamic Performancementioning

confidence: 99%

“…It should be noted that the total pressure coefficient ψ tt is obtained from the CFD simulations as reported in Refs. [50,93] as it could not be obtained from the available measured data. Since the CFD simulation results have been validated with respect to the pressure coefficient ψ and the total-to-static efficiency η ts , the predicted value of the pressure coefficient ψ tt is considered to be reliable.…”

Section: Fan Configuration and Design Parametersmentioning

confidence: 99%

“…As reported in Refs. [50,93], backflow downstream of the baseline rotor (with small HTR κ = 0.184) is present for low to high flow coefficients (ϕ = 0.10 − 0.23).…”

Section: Free-vortex Distribution Designmentioning

confidence: 99%

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Design for high efficiency of low-pressure axial fans: Use of blade sweep and vortex distribution

Wang

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Rotor-only low-pressure axial fans with small hub-to-tip diameter ratio (HTR in short) are widely used in many branches of industry, especially for cooling and ventilation purposes. As energy-related products that account for a significant proportion of the consumption of natural resources and energy, optimization of their aerodynamic performance for high efficiency is important to reduce environmental impact. Differently from low-pressure axial fans with medium to high HTR, extensive regions of backflow near the hub are often present downstream of fans with small HTR.In studies of low-pressure axial fans, Computational Fluid Dynamics (CFD) simulations have been frequently employed to analyze in detail the aerodynamic performance and the flow fields inside these machines. For optimization, according to investigations on axial fans with medium to high HTR, sweep, dihedral and skew of the blades' stacking line as well as different vortex distribution designs form important methods. However, for fans with small HTR, only few studies have been reported in the scientific literature on appropriate CFD simulation strategy, three-dimensional stacking and vortex distribution design method.The objective of this thesis is to investigate the effects of sweep, dihedral and skew on the aerodynamic performance of low-pressure axial fans with small HTR and develop an optimal vortex distribution design method for high efficiency of such fans. CFD simulations are extensively used in these investigations. Optimale Vortexverdeling OntwerpmethodeTen slotte zijn de vortexverdeling (als polynoom in de coordinaat in de spanrichting) en de HTR bepaald door het totaal-naar-statisch rendement van een referentie axiaalventilator met kleine HTR te maximaliseren. Voor vrije-vortex ontwerpen zijn analytische uitdrukkingen geformuleerd voor het maximale totaalnaar-statisch rendement en de optimale HTR. Door de vortexverdeling te combineren met een geschikte keuze voor de verdeling (in spanrichting) van de liftcoëfficiënt zijn ventilatorblad ontwerpen verkregen.De CFD-resultaten voor deze ontwerpen laten zien dat de ontwerpen gebaseerd op vrije en polynoom vortexverdelingen voldoen aan de gewenste drukstijging, met aanzienlijk verbeterde totaal-naar-statisch en totaal-naar-totaal rendementen (maximale verbetering met respectievelijk 3.9% en 4.6%).Analyses van de stromingsvelden laten zien dat er geen stromingsloslating aanwezig is in het blad-naar-blad vlak, behalve in de buurt van de naaf. Voor ontwerpen met een kleine HTR is er enige terugstroming stroomafwaarts van de rotor die de stromingsloslating nabij de naaf beïnvloedt.In het algemeen draagt het onderzoek in dit proefschrift bij aan een beter begrip van de aërodynamica van axiaalventilatoren met kleine HTR. De resultaten kunnen worden toegepast voor het ontwerpen van lagedruk axiaalventilatoren met een hoog rendement.

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Section: Sweep Dihedral and Skewsupporting

confidence: 67%

Section: Vortex Distribution Design Methodsmentioning

confidence: 99%

“…The results reported in this chapter are adapted from the published paper [93]. The research background is introduced in Sec.…”

Section: Effect Of Blade Skew On Aerodynamic Performancementioning

confidence: 99%

Section: Fan Configuration and Design Parametersmentioning

confidence: 99%

“…As reported in Refs. [50,93], backflow downstream of the baseline rotor (with small HTR κ = 0.184) is present for low to high flow coefficients (ϕ = 0.10 − 0.23).…”

Section: Free-vortex Distribution Designmentioning

confidence: 99%

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Design for high efficiency of low-pressure axial fans: Use of blade sweep and vortex distribution

Wang

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Design for High Efficiency of Low-Pressure Axial Fans With Small Hub-to-Tip Diameter Ratio by the Vortex Distribution Method

Wang

Kruyt

2022

Journal of Fluids Engineering

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Axial fans with small hub-to-tip diameter ratio (HTR) are widely used in industry, especially for cooling and ventilation purposes. Optimization of their aerodynamic performance is important, for which the vortex distribution method is well-established for axial fans with medium to high HTR. However, only few studies have focused on small HTR fans. For such fans, downstream backflow regions are often present near the hub. The vortex distribution (polynomial in spanwise coordinate) and the HTR have been determined by maximizing the total-to-static efficiency of a baseline axial fan with small HTR. For free vortex designs, analytical expressions for the maximum total-to-static efficiency and the optimal HTR have been formulated. By combining the vortex distributions thus obtained with a suitable choice for the spanwise lift coefficient distribution, fan blade designs have been established. The effects of different vortex distributions on the aerodynamic performance have been investigated, employing a Computational Fluids Dynamics (CFD) simulation strategy that has been validated for the baseline axial fan. The current CFD results show that the free and the polynomial vortex distribution designs satisfy the desired pressure rise, with significantly improved total-to-static and total-to-total efficiency (maximum improvement by 3.9% and 4.6%, respectively). For the free vortex design with larger HTR, neither flow separation nor backflow is observed. For the other designs at the design flowrate, only flow separation near the hub is found. Backflow is observed only for the designs with smaller HTR.

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Aerodynamics of Sweep in a Tandem-Bladed Subsonic Axial Compressor Rotor

Kumar

John

Chhugani

et al. 2022

Journal of Fluids Engineering

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The present numerical investigation aims to understand the effect of the chordwise sweep on the performance of a tandem rotor. In a tandem compressor rotor, diffusion is achieved through two smaller airfoils, which are positioned in a particular fashion to nullify the effect of the boundary layer separation. The forward and aft rotor blades have different blade setting angles from the hub to the tip. Executing a chordwise sweep turns out to be an invalid tandem configuration due to the intersection of the forward and the aft rotor. To overcome this, a certain amount of lean is provided to the aft rotor. Therefore, the configurations selected for the current investigation are blades with a combination of sweep and lean. Two different forward sweep configurations and one backward sweep configuration are investigated. A significant improvement in the stall margin is observed for the forward-swept rotor configuration. However, the stage loading and efficiency of the unswept rotor is found to be higher than the forward-swept rotor case. Forward sweep reduces the tip loading of the forward rotor, which delays the tip stall. Backward sweep appears to be more detrimental in terms of the operating range of the tandem rotor, causing a substantial drop in the stall margin. The performance of the swept and the unswept rotor is compared at the design mass flow and near the stall mass flow rate. The pay-off derived from the chordwise sweep is elucidated with the help of blade loading, tip leakage vortices, blockage, skin friction lines and various vortex interactions.

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Effects of Sweep, Dihedral and Skew on Aerodynamic Performance of Low-Pressure Axial Fans With Small Hub-to-Tip Diameter Ratio

Cited by 8 publications

References 25 publications

Design for high efficiency of low-pressure axial fans: Use of blade sweep and vortex distribution

Design for high efficiency of low-pressure axial fans: Use of blade sweep and vortex distribution

Design for High Efficiency of Low-Pressure Axial Fans With Small Hub-to-Tip Diameter Ratio by the Vortex Distribution Method

Aerodynamics of Sweep in a Tandem-Bladed Subsonic Axial Compressor Rotor

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