In this paper, the leakage flow in the blade tip clearance of an axial flow fan is studied, and an improved strategy for increasing the chord length of the blade tip toward the inflow direction is proposed. It has been proved that extending the tip chord can move the flow leakage backward. This results in an attenuation of the leakage vortex intensity and a mitigation of flow losses. Through comparative unsteady simulations, it is observed that a reduction in the amplitude of pressure pulsations surrounding the tip clearance and trailing edge leads to a corresponding decrease in the intensity of the noise source. The experiment results show that, under the target operating condition, the static pressure efficiency is increased by 1.02%. The amplitudes of both discrete and broadband noise are reduced, resulting in a decrease in the total sound power level at the outlet by 1.7 dB(A).
ZhuTLallier-DanielsDSanjoseM, et al.Rotating coherent flow structures as a source for narrowband tip clearance noise from axial fans. J Sound Vib2018; 417: 198–215.
2.
DuPC. Scaling of axial fan noise. Stellenbosch: Stellenbosch University, 2022. Doctoral dissertation.
3.
HassanvandMTaoWSTaiFG, et al.Unsteady simulation and investigation of tip leakage flow based on dissipation function. ASME Turbo Expo 2004: Power for Land, Sea, and Air2004.
4.
LuoBChuWZhangH. Tip leakage flow and aeroacoustics analysis of a low-speed axial fan. Aero Sci Technol2018; 98: 105700.
5.
JungJHJooWG. Effect of tip clearance, winglets, and shroud height on the tip leakage in axial flow fans. Int J Refrig2018; 93: 195–204.
6.
GourdainNLeboeufF. Unsteady simulation of an axial compressor stage with casing and blade passive treatments. J Turbomach2009; 131(2): 021013.
7.
HoughtonTDayI. Enhancing the stability of subsonic compressors using casing grooves. J Turbomach2011; 133(2): 021007.
8.
WilkinsonMBVan der SpuySJ. The effect of fan tip configuration on air-cooled condenser axial flow fan performance. Fan20152015: 1–2.
9.
CorsiniAPeruginiBRispoliF, et al.Aerodynamic workings of blade tip end-plates designed for low-noise operation in axial flow fans. Turbo Expo: Power for Land, Sea, and Air2007; 47950: 159–171.
10.
WuWZhongJ. Experimental investigation of the influence on compressor cascade characteristics at high subsonic speed with pressure surface tip winglets. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy2021; 235: 1257–1271.
11.
DeyDCamciC. Tip desensitization of an axial turbine rotor using tip platform extensions. VKI Lecture Series2004; 2: 19–23.
12.
Kharati-KoopaeeMMoallemiH. Effect of blade tip grooving on the performance of an axial fan at different tip clearances in the absence and presence of inlet guide vanes. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy2020; 234: 72–84.
13.
MenterFR. Zonal two equation kw turbulence models for aerodynamic flows. 23rd fluid dynamics, plasmadynamics, and lasers conference, 1993.
14.
MenterFRKuntzMLangtryR. Ten years of industrial experience with the SST turbulence model. Turbulence, heat and mass transfer2003; 4(1): 625–632.
15.
YimamEADemircanT. Investigation of the effects of volume change on flow structure and acoustic in a silencer. Int J Aeroacoustics2023; 22(7-8): 639–655.
16.
HurKHHaiderBASohnCH. Trailing edge serrations for noise control in axial-flow automotive cooling fans. Int J Aeroacoustics2023; 22(7-8): 713–730.
17.
MoghadamSMAMeinkeMSchröderW. Analysis of tip-leakage flow in an axial fan at varying tip-gap sizes and operating conditions. Computers & Fluids2019; 183: 107–129.
18.
JangCMFukanoTFurukawaM. Effects of the tip clearance on vortical flow and its relation to noise in an axial flow fan. JSME Int J Ser B2003; 46(3): 356–365.
19.
ZhuTCarolusTH. Axial fan tip clearance noise: experiments, Lattice–Boltzmann simulation, and mitigation measures. Int J Aeroacoustics2018; 17(1-2): 159–183.
20.
XiaoYYangGLuH, et al.Blade retrofit design to reduce the noise of an axial flow fan by mitigating the tip leakage vortex. Int J Aeroacoustics2024; 29: 1475472X241259124.
21.
HeroldGZengerFSarradjE. Influence of blade skew on axial fan component noise. Int J Aeroacoustics2017; 16(4-5): 418–430.
22.
CaoRLeeDJ. Computational study of aero-and acoustic performance of a small axial-flow fan. Int J Aeroacoustics2006; 5(3): 217–232.
23.
ParkMJLeeDJ. Sources of broadband noise of an automotive cooling fan. Appl Acoust2017; 118: 66–75.
24.
KameierFNeiseW. Rotating blade flow instability as a source of noise in axial turbomachines. J Sound Vib1997; 203(5): 833–853.
25.
LendvaiBBenedekT. Experimental and numerical investigation of the blade tip-related aeroacoustic sound source mechanisms of a ducted low-speed axial flow fan. Appl Acoust2023; 215: 109705.
26.
ANSI/AMCA Standard 210-16. ASHRAE standard 51-16, laboratory methods of testing fans for certified aerodynamic performance rating. USA, 2016.
27.
GB/T 34877.3-2017. Industrial fans -- Determination of fan sound power levels under standardized laboratory conditions -- Part 3: enveloping surface methods. China (Q Forecast Rep)2017.
28.
GB/T 4214.1-2020. Test method for noise of household and similar electrical appliances―General requirements. China, 2020.
29.
ISO 3743-1:2010. Acoustics — determination of sound power levels and sound energy levels of noise sources using sound pressure — engineering methods for small movable sources in reverberant fields Part 1: comparison method for a hard-walled test room. Europe, 2010.
30.
SturmMSanjoseMMoreauS, et al.Aeroacoustic simulation of an axial fan including the full test rig by using the lattice Boltzmann method. Fan 2015 conference, 2015.
31.
SwanepoelPCBiedermannTMvan der SpuySJ. Experimental noise reduction (aeroacoustical enhancement) of a large diameter axial flow cooling fan through a reduction in blade tip clearance. Int J Aeroacoustics2023; 22(3-4): 210–237.
