Design of Sinusoidal Leading Edge for Low-Speed Axial Fans Operating under Inflow Distortion
Abstract
:1. Introduction
2. Flow Control Using Sinusoidal Leading Edges
2.1. Design Practices and Challenges for Sinusoidal Leading Edge Rotors
- The amplitude of the sinusoid is selected between 0.05c and 0.4c, where c is the chord length of the aerodynamic profile;
- Higher values of are associated with higher aerodynamic losses at low incidence;
- The effect of the wavelength is negligible in post-stall operations; however, low values of are responsible for increased losses;
- Wavelength is normally chosen between 0.1c and 0.4c;
- Low values of and large are preferred in noise control. Tubercles are, in fact, beneficial in diminishing tonal noise at peak frequencies, and modified airfoils show reduced broadband sound pressure levels. In isolated profiles, new peaks at higher frequencies may appear;
- Sinusoid leading edge aerodynamic performance is similar for Reynolds numbers between 0.1M and 1.5M;
- Airfoil thickness plays a role, suggesting that thicker profiles are less sensitive to performance degradation due to sinusoidal shape;
- Sinusoids act as stall delayers and post-stall stabilizers, with little to no effect in stable operations. It is, therefore, not recommended to apply this modification if stable operation is expected.
2.2. Sinousoidal Leading Edges in Fan Rotors
- Sinusoidal LEs induce additional vorticity that interferes with the secondary structures that are generated in the flow passage. They also generate radial motions that interfere with and dampen the tip leakage vortex;
- The sinusoids are locally applied to control the radial velocity distribution. As an example, only the outer 30% of the blade span is usually modified with the sinusoidal profile;
- Airfoil family, thickness, and camber distributions may substantially differ from the relevant works on isolated airfoils, which mostly focus on NACA 0021 and NACA 65-021.
3. Design of Sinusoidal Leading Edge Rotor for a Low-Speed, High-Diameter Fan in an ACC Test Facility
4. Experimental and Numerical Setup
4.1. Scenario Definition
- i
- Balanced (B): The flow rate is equally divided between the two inlets;
- ii
- Mildly unbalanced (MU): the inflow has an imposed flow rate that is double that of the opposite;
- iii
- Fully unbalanced (FU): the full flow rate is imposed on one inlet only
4.2. Numerical Modeling
5. Validation
6. Results
6.1. Fan Performance under Distorted Inflow Conditions
6.2. Flow Survey with Balanced and Distorted Inflow Conditions
7. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Ref. | Application | Method. | Param. | Major Findings |
---|---|---|---|---|
[21] | Wing | Panel code | - |
|
[22,23] | NACA 65021 NACA 0021 | Exp. | = 0.03c–0.11c = 0.11c–0.43c Re = 120.000 |
|
[24] | Wing | CFD | = 0.25c–0.5c = 0.05–0.1c Re = 100.000 |
|
[25] | Model of whale flippers | Exp. | Real fin Re = 135.000–550.000 |
|
[26] | NACA 0021 | Exp. CFD | Real fin Re = 180.000 |
|
[27] | 3D wing (flippers) | Exp. | = 0.11c = 0.42c Re = 2.230 |
|
[28] | Wavy & Fenced airfoils | CFD | = 0.06c = 0.4c Re = 185.000 |
|
[29] | NACA 0015 | Exp. | = 0.0125c–0.05c = 0.0625c–0.5c Re = 63.000 |
|
[30] | NACA 0021 | Exp. (noise) | = 0.03c–0.11c = 0.11c–0.43c Re = 120.000 |
|
[31] | NACA 4415 turbine blades | CFD | = 0.1c = 0.2c Re = 50.000 |
|
[32] | NACA 4415 | CFD | = 0.025c = 0.25c Re = 183.000 |
|
Tip radius | 3680 mm |
Tip clearance | 36.8 mm |
Hub-to-tip ratio | 0.29 |
Rotational speed | 151 rpm |
Tip Reynolds number | |
Number of blades | 8 |
Rated volumetric flow rate | 333 m3/s |
Rated static pressure rise | 117 Pa |
Rated power | 57 kW |
Q | Balanced | Mild Unbalance | Full Unbalance | |||
---|---|---|---|---|---|---|
[m3/s] | Base | Sin. LE | Base | Sin. LE | Base | Sin. LE |
135 | 224.9 | 212.6 | 222.8 | 217.1 | 224.7 | 221.3 |
192 | 195.4 | 192.3 | 194.1 | 192.1 | 183.7 | 179.9 |
281 | 119.6 | 123.0 | 128.1 | 115.4 | 123.1 | 110.3 |
308 | 94.6 | 94.6 | 106.3 | 95.8 | 103.1 | 81.2 |
333 | 68.7 | 68.5 | 66.9 | 68.9 | 59.4 | 43.1 |
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Tieghi, L.; Delibra, G.; Van der Spuy, J.; Corsini, A. Design of Sinusoidal Leading Edge for Low-Speed Axial Fans Operating under Inflow Distortion. Energies 2024, 17, 1150. https://doi.org/10.3390/en17051150
Tieghi L, Delibra G, Van der Spuy J, Corsini A. Design of Sinusoidal Leading Edge for Low-Speed Axial Fans Operating under Inflow Distortion. Energies. 2024; 17(5):1150. https://doi.org/10.3390/en17051150
Chicago/Turabian StyleTieghi, Lorenzo, Giovanni Delibra, Johan Van der Spuy, and Alessandro Corsini. 2024. "Design of Sinusoidal Leading Edge for Low-Speed Axial Fans Operating under Inflow Distortion" Energies 17, no. 5: 1150. https://doi.org/10.3390/en17051150
APA StyleTieghi, L., Delibra, G., Van der Spuy, J., & Corsini, A. (2024). Design of Sinusoidal Leading Edge for Low-Speed Axial Fans Operating under Inflow Distortion. Energies, 17(5), 1150. https://doi.org/10.3390/en17051150