scholarly journals Numerical Investigation of Unsteady Flow and Aerodynamic Noise Characteristics of an Automotive Axial Cooling Fan

2020 ◽  
Vol 10 (16) ◽  
pp. 5432
Author(s):  
Jang-oh Mo ◽  
Jae-hyuk Choi
Keyword(s):  
Unsteady Flow ◽  
Flow Behavior ◽  
Near Field ◽  
Leading Edge ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Field Region ◽  
Cooling Fan ◽  
Noise Characteristics

Low-speed axial cooling fans are frequently used to manage engine temperature by ensuring that adequate quantities of air pass through heat exchangers, even at low vehicle speeds or in the idle condition. This study aims to provide a better understanding of the unsteady flow behavior around an automotive axial cooling fan with seven blades and its impact on the aerodynamic noise generation. Large Eddy Simulation (LES) near the near-field region and the Ffowcs-Williams and Hawkinbygs (FW-H) method were performed to analyze the flow characteristics around the fan and predict the aerodynamic noise emitted from the fan under a constant rotational speed of 2100 rpm. The simulation results for the velocity distributions and aerodynamic noise were compared with the experimental data measured by single hot-wire probe and in a dead-sound room. The results showed a comparatively good agreement upstream and downstream from the fan and at two different receivers of 0.5 m and 1.0 m. When the fan was rotating, a strong tonal noise numerically existed near the leading edge of the blades at the tip and amounted to 110 dB sound pressure level (SPL) caused by the increasing angles of attack with the increasing radial velocity near the ring, which caused the entire air foil to emit a low-frequency noise. Furthermore, the different SPL decay characteristics of approximately 5 dB in the near-field region and 6 dB in the far-field region were observed each time the distance from the fan doubles. The findings of this research can provide important insights into the design of axial fans with low noise and high performance.

Effects of Diffuser Vane Geometries on Compressor Performance and Noise Characteristics in a Centrifugal Compressor

2013 ◽  
Author(s):  
Yohei Morita ◽  
Nobumichi Fujisawa ◽  
Takashi Goto ◽  
Yutaka Ohta
Keyword(s):  
Centrifugal Compressor ◽  
Noise Level ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Numerical Techniques ◽  
Vaned Diffuser ◽  
Noise Characteristics ◽  
Edge Vortex ◽  
Compressor Performance

The effects of the diffuser vane geometries on the compressor performance and noise characteristics of a centrifugal compressor equipped with vaned diffusers were investigated by experiments and numerical techniques. Because we were focusing attention on the geometries of the diffuser vane’s leading edge, diffuser vanes with various leading edge geometries were installed in a vaned diffuser. A tapered diffuser vane with the tapered portion near the leading edge of the diffuser’s hub-side could remarkably reduce both the discrete frequency noise level and broadband noise level. In particular, a hub-side tapered diffuser vane with a taper on only the hub-side could suppress the development of the leading edge vortex (LEV) near the shroud side of the diffuser vane and effectively enhanced the compressor performance.

Study on the Influence of Inlet Asymmetry on Aerodynamic Noise of Cooling Fan

2020 ◽  
Author(s):  
Jie Tian ◽  
Zonghan Sun ◽  
Pengfei Chai ◽  
Hua Ouyang
Keyword(s):  
Heat Dissipation ◽  
Electronic Device ◽  
Numerical Study ◽  
Rotor Blades ◽  
Aerodynamic Noise ◽  
Sampling Point ◽  
Inlet Flow ◽  
Cooling Fan ◽  
Noise Characteristics ◽  
Correction Technique

Abstract Experimental and numerical studies on the aerodynamic noise characteristics of a variable-speed axial fan commonly used for electronic device heat dissipation were conducted. First, the far-field noise spectrum of the fan was measured using a microphone array on the contour plane of the fan axis. The spectral analysis indicated that the discrete single-tone noise energy ratio was high, which indicates that it was the dominant aerodynamic noise. Afterwards, the double-uniform sampling point mode correction technique, which is based on the circumferential acoustic mode measurement method, was used to obtain the modal distribution on the inlet and outlet sides of the cooling fan. The influence of inlet unevenness on the cooling fan was identified. The traditional Tyler-Sofrin rotor-stator interaction formula was modified to account for the non-axisymmetric shape of the fan inlet bellmouth. The validity of the modified formula was verified by measuring the circumferential acoustic modes of three cooling fans with different rotor and strut counts. Furthermore, a CFD numerical study was conducted using Fluent to understand the influence of uneven inlet flow. The results showed that uneven inlet flow significantly affects the size and distribution of unsteady pulses on the rotor blades, which cause regular, periodic changes as the rotor blades rotate. Interactions between rotor blades and inlet unevenness were observed via the POD method as well. The discussion of the circumferential modes from aerodynamic noise of an axial flow cooling fan can act as a reference for further cooling fan noise reduction measures.

scholarly journals Development of an Improved LMD Method for the Low-Frequency Elements Extraction from Turbine Noise Background

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 805
Author(s):  
Lida Liao ◽  
Bin Huang ◽  
Qi Tan ◽  
Kan Huang ◽  
Mei Ma ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Wind Turbine ◽  
Condition Monitoring ◽  
Renewable Energy Sources ◽  
Near Field ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Human Society ◽  
Noise Background

Given the prejudicial environmental effects of fossil-fuel based energy production, renewable energy sources can contribute significantly to the sustainability of human society. As a clean, cost effective and inexhaustible renewable energy source, wind energy harvesting has found a wide application to replace conventional energy productions. However, concerns have been raised over the noise generated by turbine operating, which is helpful in fault diagnose but primarily identified for its adverse effects on the local ecosystems. Therefore, noise monitoring and separation is essential in wind turbine deployment. Recent developments in condition monitoring provide a solution for turbine noise and vibration analysis. However, the major component, aerodynamic noise is often distorted in modulation, which consequently affects the condition monitoring. This study is conducted to explore a novel approach to extract low-frequency elements from the aerodynamic noise background, and to improve the efficiency of online monitoring. A framework built on the spline envelope method and improved local mean decomposition has been developed for low-frequency noise extraction, and a case study with real near-field noises generated by a mountain-located wind turbine was employed to validate the proposed approach. Results indicate successful extractions with high resolution and efficiency. Findings of this research are also expected to further support the fault diagnosis and the improvement in condition monitoring of turbine systems.

Study on the Influence of Inlet Asymmetry on Aerodynamic Noise of Cooling Fan

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Jie Tian ◽  
Zonghan Sun ◽  
Pengfei Chai ◽  
Hua Ouyang
Keyword(s):  
Heat Dissipation ◽  
Electronic Device ◽  
Numerical Study ◽  
Rotor Blades ◽  
Aerodynamic Noise ◽  
Sampling Point ◽  
Inlet Flow ◽  
Cooling Fan ◽  
Noise Characteristics ◽  
Correction Technique

Abstract Experimental and numerical studies on the aerodynamic noise characteristics of a variable-speed axial fan commonly used for electronic device heat dissipation were conducted. First, the far-field noise spectrum of the fan was measured using a microphone on the contour plane of the fan axis. The spectral analysis indicated that the discrete single-tone noise energy ratio was high, which indicates that it was the dominant aerodynamic noise. Afterward, the double-uniform sampling point mode correction technique, which is based on the circumferential acoustic mode measurement method, was used to obtain the modal distribution on the inlet and outlet sides of the cooling fan. The influence of inlet unevenness on the cooling fan was identified. The traditional Tyler–Sofrin rotor–stator interaction formula was modified to account for the nonaxisymmetric shape of the fan inlet bellmouth. The validity of the modified formula was verified by measuring the circumferential acoustic modes of three cooling fans with different rotor and strut counts. Furthermore, a computational fluid dynamics (CFD) numerical study was conducted using Fluent to understand the influence of uneven inlet flow. The results showed that uneven inlet flow significantly affects the size and distribution of unsteady pulses on the rotor blades, which cause regular, periodic changes as the rotor blades rotate. Interactions between rotor blades and inlet unevenness were observed via the proper orthogonal decomposition (POD) method as well. The discussion of the circumferential modes from aerodynamic noise of an axial flow cooling fan can act as a reference for further cooling fan noise reduction measures.

Calculation of Flow through Cascades of Blades Having Relative Motion and the Generation of Alternating Pressures and Forces Due to Interaction Effects

1967 ◽  
Vol 182 (1) ◽  
pp. 229-242 ◽  
Author(s):  
R. Parker
Keyword(s):  
Near Field ◽  
Primary Source ◽  
Low Noise ◽  
Frame Of Reference ◽  
Frequency Noise ◽  
Noise Radiation ◽  
Blade Row ◽  
Time Variations ◽  
Flow Through ◽  
Blade Row Interaction

A method is given for calculating the incompressible flow of a perfect fluid through multiple cascades of blades with one or more cascades moving relative to the frame of reference. Finite differences are used and the stream function evaluated by relaxation. From this velocities and pressures are calculated throughout the field for a sequence of relative blade positions allowing the spatial and time variations to be obtained. The method is applied to an i.g.v.-rotor combination with three values of axial spacing. The results show that the mechanism of blade row interaction is that the i.g.v. prevents accelerations of the fluid in the direction normal to the i.g.v. camber line which would occur if the i.g.v. were not present. The resultant pressure differences across the i.g.v. are the primary source of alternating forces and provide sources of discrete frequency noise at typical blade row axial spacings. The present investigation is confined to the near field and estimation of noise radiation is beyond its scope; however, if the analysis is used to design blades producing the minimum fluctuating pressures, relatively low noise radiation should result.

scholarly journals Research on High-Resolution Miniaturized MEMS Accelerometer Interface ASIC

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7280
Author(s):  
Xiangyu Li ◽  
Yangong Zheng ◽  
Xiangyan Kong ◽  
Yupeng Liu ◽  
Danling Tang
Keyword(s):  
High Precision ◽  
Closed Loop ◽  
Low Noise ◽  
Oxide Semiconductor ◽  
High Signal ◽  
Cmos Process ◽  
Frequency Noise ◽  
Interface Circuit ◽  
Noise Characteristics ◽  
Mems Accelerometers

High-precision microelectromechanical system (MEMS) accelerometers have wide application in the military and civil fields. The closed-loop microaccelerometer interface circuit with switched capacitor topology has a high signal-to-noise ratio, wide bandwidth, good linearity, and easy implementation in complementary metal oxide semiconductor (CMOS) process. Aiming at the urgent need for high-precision MEMS accelerometers in geophones, we carried out relevant research on high-performance closed-loop application specific integrated circuit (ASIC) chips. According to the characteristics of the performance parameters and output signal of MEMS accelerometers used in geophones, a high-precision closed-loop interface ASIC chip based on electrostatic time-multiplexing feedback technology and proportion integration differentiation (PID) feedback control technology was designed and implemented. The interface circuit consisted of a low-noise charge-sensitive amplifier (CSA), a sampling and holding circuit, and a PID feedback circuit. We analyzed and optimized the noise characteristics of the interface circuit and used a capacitance compensation array method to eliminate misalignment of the sensitive element. The correlated double sampling (CDS) technology was used to eliminate low-frequency noise and offset of the interface circuit. The layout design and engineering batch chip were fabricated by a standard 0.35 μm CMOS process. The active area of the chip was 3.2 mm × 3 mm. We tested the performance of the accelerometer system with the following conditions: power dissipation of 7.7 mW with a 5 V power supply and noise density less than 0.5 μg/Hz1/2. The accelerometers had a sensitivity of 1.2 V/g and an input range of ±1.2 g. The nonlinearity was 0.15%, and the bias instability was about 50 μg.

scholarly journals Experimental and Numerical Study on Gas-Liquid Two-Phase Flow Behavior and Flow Induced Noise Characteristics of Radial Blade Pumps

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 920 ◽  
Author(s):  
Qiaorui Si ◽  
Chunhao Shen ◽  
Asad Ali ◽  
Rui Cao ◽  
Jianping Yuan ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Numerical Study ◽  
Flow Behavior ◽  
Internal Flow ◽  
Suction Side ◽  
Low Noise ◽  
Stable Operation ◽  
Phase Flow ◽  
Two Phase ◽  
Noise Characteristics

Miniature drainage pumps with a radial blade are widely used in situations with critical constant head and low noise requests, but the stable operation state is often broken up by the entraining gas. In order to explore the internal flow characteristics under gas–liquid two phase flow, pump performance and emitted noise measurements were processed under different working conditions. Three-dimensional numerical calculations based on the Euler inhomogeneous model and obtained experimental boundaries were carried out under different inlet air void fractions (IAVFs). A hybrid numerical method was proposed to obtain the flow-induced emitted noise characteristics. The results show there is little influence on pump characteristics when the IAVF is less than 1%. The pump head slope degradation was found to increase with air content. The bubbles adhere to the impeller hub on the blade’s suction side and spread to the periphery with a big IAVF, leading to unstable operation. It is obvious that vortices appear inside the impeller flow passage as IAVF reaches 6.5%. The two-phase flow pattern has a small effect on the characteristic frequency distribution of pressure fluctuation and emitted noise, but the corresponding pulsation intensity and noise level will increase. The study could provide some reference for low noise design of the drainage pump.

Near-Field Noise Prediction for Landing Gear Based on Detached Eddy Simulations

2014 ◽  
Vol 472 ◽  
pp. 105-110
Author(s):  
Ning Hu ◽  
Xuan Hao ◽  
Cheng Su ◽  
Wei Min Zhang ◽  
Han Dong Ma
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Sound Pressure ◽  
Near Field ◽  
Separated Flow ◽  
Landing Gear ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

A four-wheel rudimentary landing gear is studied numerically by detached eddy simulation (DES) based on the Spalart-Allmaras turbulence model. The surface sound pressure level and sound pressure spectra are calculated using the obtained unsteady flow field. The investigation shows that DES can describe the steady and unsteady properties in the flow around rudimentary landing gear. It can give reasonable results since the flow around the landing gear is a massive separated flow. The results prove the feasibility of DES type methods in massive separated unsteady flow field and aerodynamic noise prediction for landing gear, and can be used in the study of landing gear noise reduction.

scholarly journals Analysis of Aerodynamic Noise Characteristics of High-Speed Train Pantograph with Different Installation Bases

2019 ◽  
Vol 9 (11) ◽  
pp. 2332 ◽  
Author(s):  
Yongfang Yao ◽  
Zhenxu Sun ◽  
Guowei Yang ◽  
Wen Liu ◽  
Prasert Prapamonthon
Keyword(s):  
High Speed ◽  
Near Field ◽  
Complex Structure ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Noise Sources ◽  
Eddy Simulation ◽  
Noise Characteristics ◽  
Large Eddy ◽  
Flow Phenomena

The high-speed-train pantograph is a complex structure that consists of different rod-shaped and rectangular surfaces. Flow phenomena around the pantograph are complicated and can cause a large proportion of aerodynamic noise, which is one of the main aerodynamic noise sources of a high-speed train. Therefore, better understanding of aerodynamic noise characteristics is needed. In this study, the large eddy simulation (LES) coupled with the acoustic finite element method (FEM) is applied to analyze aerodynamic noise characteristics of a high-speed train with a pantograph installed on different configurations of the roof base, i.e. flush and sunken surfaces. Numerical results are presented in terms of acoustic pressure spectra and distributions of aerodynamic noise in near-field and far-field regions under up- and down-pantograph as well as flushed and sunken pantograph base conditions. The results show that the pantograph with the sunken base configuration provides better aerodynamic noise performances when compared to that with the flush base configuration. The noise induced by the down-pantograph is higher than that by the up-pantograph under the same condition under the pantograph shape and opening direction selected in this paper. The results also indicate that, in general, the directivity of the noise induced by the down-pantograph with sunken base configuration is slighter than that with the flush configuration. However, for the up-pantograph, the directivity is close to each other in Y-Z or X-Z plane whether it is under flush or sunken roof base condition. However, the sunken installation is still conducive to the noise environment on both sides of the track.

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