Load-oriented aerodynamic design approach of low-speed axial fans in the preliminary design stage

Abstract

For low-speed axial-flow fans, the arbitrary vortex design method is widely used in high total pressure rise design requirement or small hub-to-tip ratio design applications. In the conventional arbitrary vortex design method, the total pressure rise of the fan blade commonly increases from hub to tip due to greater work potential near the tip. However, the high aerodynamic load in the blade tip region will inevitably result in an intensification of the tip leakage flow which limits the improvement of fan aerodynamic efficiency, especially for fans with a high total pressure rise design requirement. To solve this problem, this paper has developed a load-oriented aerodynamic design approach to take into account the spanwise work distribution of the fan in the preliminary design stage so as to reduce the potential loss caused by overloading of blade airfoil sections in local spanwise fractions and enhance the fan aerodynamic performances. In specific, the spanwise work distribution is firstly parameterized to control the blade load along the spanwise direction. Then, the diffusion factor is correlated to the total pressure loss coefficient to achieve a rapid evaluation of blade aerodynamic performance. In the meanwhile, the spanwise work of the blade airfoil sections can be automatically optimized to achieve an optimal load distribution. Finally, two axial-flow fans are designed based on the conventional arbitrary vortex design method and the load-oriented aerodynamic design approach respectively. The computational results show that the load-oriented designed fan has achieved a lower aerodynamic loss near the blade tip compared with the conventional arbitrary vortex designed fan. At the design point, an approximately 1.5% increment of adiabatic efficiency is also obtained. Moreover, over the entire operating range, the load-oriented designed fan shows higher adiabatic efficiency than the conventional arbitrary vortex designed fan, without sacrificing the total pressure rise. The motivation of this work is to offer useful guidelines for high-performance low-speed axial fan design under the requirements of high total pressure rise and small hub-to-tip ratio applications.

Keywords

spanwise work distribution aerodynamic design approach low-speed axial fan

Get full access to this article

View all access options for this article.

References

Eck

. Fans. Oxford, UK: Pergamon Press, 1973.

Wallis

. Axial flow fans and ducts. Malabar, FL: Krieger Publishing Company, 1993.

. Numerical investigations of the influences of valve spool structure on the eccentric jet flow characteristic in high-pressure angle valves. Energy 2024; 298: 131378.

. Optimization design method based on parameter reduction and active subspaces: redistribution of chordwise loading at blade tips in a transonic axial-flow fan. Phys Fluids 2024; 36(9): 095103.

Kahane

. “Investigation of axial-flow fan and compressor rotors designed for three-dimensional flow”. Washington, D.C: NASA, 1947.

Wallis

. Axial flow fans, design and practice. London: George Newnes, 1961.

Downie

Thompson

Wallis

. An engineering approach to blade designs for low to medium pressure rise rotor-only axial fans. Exp Therm Fluid Sci 1993; 6(4): 376–401.

Vad

. Correlation of flow path length to total pressure loss in diffuser flows. Proc Inst Mech Eng A J Power Energy 2011; 225(4): 481–496.

Masi

Castegnaro

Lazzaretto

. A criterion for the preliminary design of high-efficiency tube-axial fans. New York City: ASME Paper No. GT2016-56960, 2016.

10.

Castegnaro

Masi

Lazzaretto

. Preliminary experimental assessment of the performance of tube-axial fans designed with different vortex criteria. In: Proceedings of 12th European conference on turbomachinery fluid dynamics & thermodynamics, Stockholm, Sweden, April 3-7, 2017.

11.

Howell

. Fluid dynamics of axial compressors. Proc Inst Mech Eng 1945; 153(1): 441–452.

12.

Louw

Bruneau

PRP

von Backström

, et al. The design of an axial flow fan for application in large air-cooled heat exchangers. New York City: ASME Paper No. GT2016-56960, 2012.

13.

Lieblein

Schwenk

Broderick

. “Diffusion factor for estimating losses and limiting blade loadings in axial-flow-compressor blade elements,”. Washington, D.C: NASA, 1953.

14.

Robbins

Jackson

Lieblein

. “Blade element flow in annular cascades”. Washington, D.C: NASA, 1965.

15.

Lieblein

Roudebush

. “Theoretical loss relations for low-speed two-dimensional-cascade flow”. Washington, D.C: NASA, 1956.

16.

Teng

Zhu

, et al. Effective strategy of non-axisymmetric endwall contouring in a linear compressor cascade. Proc Inst Mech Eng G J Aerosp Eng 2022; 236(8): 1473–1487.

17.

Zhao

Vahdati

. Uncertainty quantification of spalart-allmaras turbulence model coefficients for simplified compressor flow features. J Fluid Eng 2020; 142(9): 091501.

18.

Sun

Wang

Chen

. Design, modification and optimization of an ultra-high-load transonic low-reaction aspirated compressor. Aero Sci Technol 2020; 105(2020): 105975.

19.

Shi

, et al. Robust design of a fan rotor blade by sweep and lean optimization with surface roughness. Proc Inst Mech Eng G J Aerosp Eng 2023; 237(4): 914–924.

20.

Denton

. Loss mechanisms in turbomachines. J Turbomach 1993; 115(4): 621–656.

21.

Luo

Chu

Zhang

. Tip leakage flow and aeroacoustics analysis of a low-speed axial fan. Aero Sci Technol 2020; 98: 105700.

22.

Storer

Cumpsty

. An approximate analysis and prediction method for tip clearance loss in axial compressors. J Turbomach 1994; 116(4): 648–656.

23.

Vad

. Radial fluid migration and endwall blockage in axial flow rotors. Proc Inst Mech Eng A J Power Energy 2010; 224(3): 399–417.