Noise reduction effect of leading-edge serrations on axial fan

Abstract This paper imitates the raised structure of the leading edge of the humpback whale fin limbs, designed six bionic blades. The aerodynamic analysis show that: the wave leading edge blade can improve the total pressure efficiency of the axial flow fan, and under off-design conditions, the aerodynamic performance of bionic fan is better than that of prototype fan. The noise analysis shows that: under the condition of constant wave number, increasing wave amplitude can reduce the overall sound pressure level at the monitoring point, in the middle and high frequency range, the sound pressure level of the bionic fan at the monitoring point is significantly lower than that of the prototype fan, and the noise reduction effect increases with the increase of wave amplitude; under the condition of constant wave amplitude, increasing the wave number can reduce the fan noise. At a certain wave number and amplitude, the overall sound pressure level of the bionic fan at the monitoring point is at most 2.91 dB lower than that of the prototype fan. In this paper, the noise reduction effect of increasing wave number is more obvious than that of increasing wave amplitude.

Download Full-text

Aeroacoustic Characteristics of Cavity and Effect Study of Mesh on Noise Suppression

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.421.104 ◽

2013 ◽

Vol 421 ◽

pp. 104-109

Author(s):

Jing Sun ◽

Guang Jun Yang ◽

Jian Jun Liu

Keyword(s):

Noise Reduction ◽

Noise Suppression ◽

Flow Characteristics ◽

Leading Edge ◽

Cavity Flow ◽

Noise Spectrum ◽

Effect Study ◽

Suppression Effect ◽

Reduction Effect ◽

Suppression Effects

To explore the noise suppression effect of mesh on cavity, the wind tunnel experiment is carried out based on the analysis of clean cavity flow characteristics. The meshes are arranged both in the cavity and at the leading edge of the cavity. Through the analysis of pressure distribution on the cavity bottom and the noise spectrum monitored at front and rear walls respectively, noise suppression effects of mesh programs relative to the clean cavity and changes in the flow field are studied, the results show that the mesh inside the cavity has a better noise reduction effect. The work in this paper provides an effective way for cavity noise reduction.

Download Full-text

Noise Reduction Effect of Superhydrophobic Surfaces with Streamwise Strip of Channel Flow

Applied Sciences ◽

10.3390/app11093869 ◽

2021 ◽

Vol 11 (9) ◽

pp. 3869

Author(s):

Chen Niu ◽

Yongwei Liu ◽

Dejiang Shang ◽

Chao Zhang

Keyword(s):

Reynolds Number ◽

Drag Reduction ◽

Noise Reduction ◽

Channel Flow ◽

Superhydrophobic Surface ◽

Sound Field ◽

Flow Noise ◽

Slip Boundary ◽

Eddy Simulation ◽

Reduction Effect

Superhydrophobic surface is a promising technology, but the effect of superhydrophobic surface on flow noise is still unclear. Therefore, we used alternating free-slip and no-slip boundary conditions to study the flow noise of superhydrophobic channel flows with streamwise strips. The numerical calculations of the flow and the sound field have been carried out by the methods of large eddy simulation (LES) and Lighthill analogy, respectively. Under a constant pressure gradient (CPG) condition, the average Reynolds number and the friction Reynolds number are approximately set to 4200 and 180, respectively. The influence on noise of different gas fractions (GF) and strip number in a spanwise period on channel flow have been studied. Our results show that the superhydrophobic surface has noise reduction effect in some cases. Under CPG conditions, the increase in GF increases the bulk velocity and weakens the noise reduction effect. Otherwise, the increase in strip number enhances the lateral energy exchange of the superhydrophobic surface, and results in more transverse vortices and attenuates the noise reduction effect. In our results, the best noise reduction effect is obtained as 10.7 dB under the scenario of the strip number is 4 and GF is 0.5. The best drag reduction effect is 32%, and the result is obtained under the scenario of GF is 0.8 and strip number is 1. In summary, the choice of GF and the number of strips is comprehensively considered to guarantee the performance of drag reduction and noise reduction in this work.

Download Full-text

Investigation on the AMDT Core Vibration by Modal Analysis and Validation of the Noise Reduction Effect by Testing Platform

2020 IEEE International Conference on High Voltage Engineering and Application (ICHVE) ◽

10.1109/ichve49031.2020.9279632 ◽

2020 ◽

Author(s):

Daosheng Liu ◽

Changwan Cai ◽

Yahui Zhao ◽

Muqiu Yan

Keyword(s):

Noise Reduction ◽

Modal Analysis ◽

Testing Platform ◽

Reduction Effect

Download Full-text

Research on a noise control device. (5th report The noise reduction effect of application to a machine and its prediction method by a scale model experiment)

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series C ◽

10.1299/kikaic.52.2863 ◽

1986 ◽

Vol 52 (483) ◽

pp. 2863-2868

Author(s):

Keiichiro MIZUNO ◽

Hisayoshi SEKIGUTI ◽

Kazuyoshi IIDA

Keyword(s):

Noise Reduction ◽

Model Experiment ◽

Noise Control ◽

Prediction Method ◽

Control Device ◽

Scale Model ◽

Reduction Effect

Download Full-text

Spanwise varying porosity for the enhancement of leading-edge noise reduction

AIAA AVIATION 2021 FORUM ◽

10.2514/6.2021-2191 ◽

2021 ◽

Author(s):

Lorna J. Ayton ◽

Orestis Karapiperis ◽

Manuj Awasthi ◽

Danielle Moreau ◽

Con J. Doolan

Keyword(s):

Noise Reduction ◽

Leading Edge

Download Full-text

A study of sound sources and unsteady surface pressure in an axial fan

Modern Physics Letters B ◽

10.1142/s0217984921502675 ◽

2021 ◽

pp. 2150267

Author(s):

Bo Luo ◽

Wuli Chu ◽

Song Yan ◽

Zhengjing Shen ◽

Haoguang Zhang

Keyword(s):

Leading Edge ◽

Noise Spectrum ◽

Industrial Applications ◽

Acoustic Analogy ◽

Dynamics Modeling ◽

Axial Fan ◽

Sound Sources ◽

Recirculating Flow ◽

Aerodynamic Interaction ◽

Blade Tip

The noise emitted from an axial fan has become one of the primary concerns for many industrial applications. This paper presents the work to predict the noise generation and investigate sound sources in a low speed axial fan. Computational fluid dynamics modeling is conducted using Scale Adaptive Simulation for the unsteady flow field. The sound predictions by the acoustic analogy are in good agreement with the experimental data. The results from this study show that the aerodynamic interaction between the blades and outlet vanes has a major contribution to the radiated noise spectrum. Two types of sources of narrowband humps are identified in the axial fan. The first is found at the leading edge of the blade tip, which is related to the interaction of coherent flow structures in the blade tip region. The second is found in the vicinity of the blade hub, which can be attributed to the recirculating flow and hub vortex. The noise below the frequency of 1500 Hz is mainly due to the blade-outlet vane aerodynamic interaction, manifested as the tonal sound at BPF and its harmonics, whereas above 1500 Hz the broadband component of sound is mainly related to the turbulent boundary layers.

Download Full-text

Comparison of Noise Reduction Performance Evaluation Methods for Low-Noise Pavement in Korea- Part

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-2260 ◽

2021 ◽

Vol 263 (4) ◽

pp. 2930-2939

Author(s):

Byungchae Kim ◽

Hyunjin Kim ◽

Wonuk Kang

Keyword(s):

Noise Reduction ◽

Noise Level ◽

Measurement Method ◽

Road Traffic ◽

Low Noise ◽

Management Standards ◽

Close Proximity ◽

Porous Pavement ◽

Reduction Effect ◽

Measurement Location

In Korea, road noise is assessed as a measurement method of exterior noise emitted by road vehicle for management standards by the National Institute of Environmental Sciences. In this method, the noise felt at the actual pickup point is measured as LAeq (the roadside equivalent noise level). Recently, to clarify the standard for measuring noise on low-noise pavements, the CPX (ISO11819-2; Close-proximity method) was first introduced in the Porous Pavement Guidelines of the Ministry of Land, Infrastructure and Transport. According to ISO, the CPX adopts the side microphone as a mandatory measurement location, and the rear optional. The side location has been a mandatory due to its high correlation with SPB (ISO 11819-1, Statistical Pass-by method). However, according to our previous study on the correlation evaluation between L and CPX rear microphone noise level, both noise reduction effect was about 9-12 dB(A) showed a high correlation in Korea where heavy road traffic is common. The following study aims to show the consistent correlation between the L and CPX rear noise level. Furthermore, it is intended to be helpful in selecting the location of the CPX microphone that can most effectively represent the actual noise on the low-noise pavement in Korea.

Download Full-text

A Study on the Fan Tone Noise Reduction with Wavy Leading Edge OGV

AIAA AVIATION 2021 FORUM ◽

10.2514/6.2021-2258 ◽

2021 ◽

Author(s):

Hang Tong ◽

Kangshen Xiang ◽

Liangji Zhang ◽

Lin Li ◽

Weijie Chen ◽

...

Keyword(s):

Noise Reduction ◽

Leading Edge

Download Full-text

Experiments on an Axial Fan Stage: Time-Resolved Analysis of Rotating Instability Modes

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4028686 ◽

2015 ◽

Vol 137 (6) ◽

Cited By ~ 14

Author(s):

Benjamin Pardowitz ◽

Ulf Tapken ◽

Lars Neuhaus ◽

Lars Enghardt

Keyword(s):

Leading Edge ◽

Operating Conditions ◽

Tip Clearance ◽

Axial Fan ◽

Time Resolved ◽

Instability Waves ◽

Instability Modes ◽

Mode Decomposition ◽

Rotating Instability ◽

Annular Cascade

Rotating instability (RI) occurs at off-design conditions in axial compressors, predominantly in rotor configurations with large tip clearances. Characteristic spectral signatures with side-by-side peaks below the blade passing frequency (BPF) are typically referred to RI located in the clearance region next to the leading edge (LE). Each peak can be assigned to a dominant circumferential mode. RI is the source of the clearance noise (CN) and an indicator for critical operating conditions. Earlier studies at an annular cascade pointed out that RI modes of different circumferential orders occur stochastically distributed in time and independently from each other, which is contradictory to existing explanations of RI. Purpose of the present study is to verify this generally with regard to axial rotor configurations. Experiments were conducted on a laboratory axial fan stage mainly using unsteady pressure measurements in a sensor ring near the rotor LE. A mode decomposition based on cross spectral matrices was used to analyze the spectral and modal RI patterns upstream of the rotor. Additionally, a time-resolved analysis based on a spatial discrete-Fourier-transform (DFT) was applied to clarify the temporal characteristics of the RI modes and their potential interrelations. The results and a comparison with the previous findings on the annular cascade corroborate a new hypothesis about the basic RI mechanism. This hypothesis implies that instability waves of different wavelengths are generated stochastically in a shear layer resulting from a backflow in the tip clearance region.

Download Full-text