Study on the effect of separation and reattachment flow between blades on fan noise

With the growth of the EV/HV market, the main cause of cabin noise has changed from engine driving sound to air conditioner noise. The blower noise is the largest in the air conditioner noise, and the noise reduction is urgent. Separated and reattached flows between fan blades are considered to be the main sources of blower noise. In the past, we tried to reduce the noise by reducing the separation. This time, the blade shape to further reduce the separation was produced and evaluated. As a result, the noise was greatly reduced, but a new problem was found that there was a flow velocity condition in which the noise increased despite the small separation. Therefore, we visualized the flow between blades by PIV, investigated the state of separated and reattached flow in detail, and investigated the factors related to noise increase and decrease by measuring noise and pressure fluctuation of blade surface simultaneously. As a result, it was found that the noise generation condition in the separation reattachment flow between blades is not only the size of separation but also the distance of separation shear layer from blade surface and the strength of vortex generated in shear layer.

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Unique Slow Crack Growth Behavior of Isotactic Polypropylene: The Role of Shear Layer-Spherulites Layer Alternated Structure

Polymers ◽

10.3390/polym12112746 ◽

2020 ◽

Vol 12 (11) ◽

pp. 2746

Author(s):

Mingjin Liu ◽

Jiaxu Luo ◽

Jin Chen ◽

Xueqin Gao ◽

Qiang Fu ◽

...

Keyword(s):

Shear Layer ◽

Crack Growth ◽

Isotactic Polypropylene ◽

Slow Crack Growth ◽

Crack Growth Behavior ◽

Polymer Science ◽

The Past ◽

Propagation Behavior ◽

Crack Propagation Behavior

With the development of polymer science, more attention is being paid to the longevity of polymer products. Slow crack growth (SCG), one of the most important factors that reveal the service life of the products, has been investigated widely in the past decades. Here, we manufactured an isotactic polypropylene (iPP) sample with a novel shear layer–spherulites layer alternated structure using multiflow vibration injection molding (MFVIM). However, the effect of the alternated structure on the SCG behavior has never been reported before. Surprisingly, the results showed that the resistivity of polymer to SCG can be enhanced remarkably due to the special alternated structure. Moreover, this sample shows unique slow crack propagation behavior in contrast to the sample with the same thickness of shear layer, presenting multiple microcracks in the spherulites layer, which can explain the reason of the resistivity improvement of polymer to SCG.

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On the Mechanism of Noise Generation in the Sirocco Fan for Automobile Air Conditioner

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.74.2552 ◽

2008 ◽

Vol 74 (748) ◽

pp. 2552-2559 ◽

Cited By ~ 1

Author(s):

Yasuhiko SAKAI ◽

Takaaki KATO ◽

Yuu MORIGUCHI ◽

Masaharu SAKAI ◽

Kouji ITO ◽

...

Keyword(s):

Noise Generation ◽

Air Conditioner ◽

Automobile Air Conditioner ◽

Sirocco Fan

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Research on Fan Noise Generation

The Journal of the Acoustical Society of America ◽

10.1121/1.1912993 ◽

1972 ◽

Vol 51 (5A) ◽

pp. 1427-1438 ◽

Cited By ~ 9

Author(s):

M. J. Benzakein

Keyword(s):

Noise Generation ◽

Fan Noise

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Discrete Frequency Noise Generation From an Axial Flow Fan Blade Row

Journal of Basic Engineering ◽

10.1115/1.3424944 ◽

1970 ◽

Vol 92 (1) ◽

pp. 37-43 ◽

Cited By ~ 10

Author(s):

Ramani Mani

Keyword(s):

Three Dimensional ◽

Axial Flow ◽

Acoustic Energy ◽

Frequency Noise ◽

Noise Generation ◽

Two Dimensional ◽

Axial Flow Fan ◽

Fan Noise ◽

Blade Row ◽

Fan Blade

An analysis is presented which treats the noise generation from an axial flow fan row by given forces including the effects of a moving medium. The linearization of Euler’s equations to yield tractable problems for fan noise is discussed. The three-dimensional problem is decomposed into several two-dimensional problems. Finally, full details are given of a two-dimensional analysis to predict the amounts of acoustic energy, at the blade passing frequency and its harmonics, radiated up and downstream of a blade row due to its interaction with a neighboring row.

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Fan Noise and Control: Turbine Noise Generation, Reduction, and Prediction

Aeroacoustics: STOL Noise: Airframe and Airfoil Noise ◽

10.2514/5.9781600865190.0109.0138 ◽

1976 ◽

pp. 109-138

Keyword(s):

Noise Generation ◽

Fan Noise ◽

And Control

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LES of the Flow and Acoustics Generated by an Aircraft Fan Running in the Vicinity of the Ground

Volume 6: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68397 ◽

2005 ◽

Author(s):

Dragos¸ Moroianu ◽

Arne Karlsson ◽

Laszlo Fuchs

Keyword(s):

Sound Pressure ◽

Near Field ◽

Pressure Level ◽

Velocity Variation ◽

Noise Generation ◽

Fan Noise ◽

Blade Passage ◽

Homogeneous Wave ◽

Sound Spectrum ◽

Homogeneous Wave Equation

An important component of the aircraft generated noise, especially ahead of it, is the fan noise created by the high velocity variation near the blades and the interaction of the rotating fan with the fluid. In order to predict the sound, the method used involves the acoustical analogy developed by Ffowcs Williams and Hawkings. Computation of the flow field is performed in the incompressible LES framework, while the noise is evaluated using a non-homogeneous wave equation. In this work the influence of the angle between the fan and ground, on the total sound spectrum, the noise generation and the noise propagation is investigated. It is found that the near field is dominated by the blade passage frequency and an upward inclination of the fan will produce a slightly different sound pressure level than a horizontal or downward inclination.

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The Influence of Non-Uniform Impeller on the Cross Flow Fan Noise

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.693.251 ◽

2016 ◽

Vol 693 ◽

pp. 251-256

Author(s):

Zhi Qiang Yang ◽

C.J. Wu

Keyword(s):

Pressure Fluctuations ◽

Flow Characteristics ◽

Cross Flow ◽

Internal Flow ◽

Broadband Noise ◽

Aerodynamic Noise ◽

Air Conditioner ◽

Fan Noise ◽

Power Spectral ◽

Cross Flow Fan

The aerodynamic noise of a cross flow fan with uneven blade spacing in room air-conditioner was simulated by computational aerodynamic acoustics (CAA) method. It is detailed to analyze the vorticity distribution of the flow field and the power spectral density of measured points’ pressure fluctuations, and the results demonstrate the non-uniform impeller used in this paper can significantly improve internal flow characteristics. Thus the broadband noise got reduced.

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Expanding Horizons on a Diminishing Planet

PEDIATRICS ◽

10.1542/peds.67.5.771 ◽

1981 ◽

Vol 67 (5) ◽

pp. 771-774

Author(s):

Donald A. Henderson

Keyword(s):

Child Health ◽

Heat Wave ◽

Air Conditioner ◽

Medical Organization ◽

Surgeon General ◽

The Past ◽

Health Goals ◽

Atom Bomb ◽

Revisionist History ◽

Better Than

I am honored and pleased to be given the opportunity to participate with you today in your celebration of an extraordinary 50 years of achivement1—a history which, even when viewed through a critical retrospective lens, can bear with distinction the appellations of prescient, bold, imaginative, and progressive. I doubt there is today any other professional medical organization which can display with pride such a record without developing a revisionist history adapted to the flow of subsequent events. It is obvious that the Academy has led, not followed; that it has deliberately and aggressively pursued concepts in prevention which were often more visionary than those advocated by leaders in my own field; and that this year, it has boldly extended its purview to embrace an even broader range of objectives in stating its "National Child Health Goals."2 Rightly, the Academy has recognized that solutions today must transcend the conventional boundaries of curative medicine. In enunciating your goals, you have implicitly recognized this in identifying objectives which will require an active partnership with educators and environmentalists, behavioral scientists, and politicians alike in the interests of healthier children. The past 50 years have witnessed unprecedented changes in medicine, in science in its totality—indeed, in our entire social structure and values. We can be confident that the next 50 years will bring even more revolutionary changes, but can we anticipate them any better than we anticipated the computer, organ transplantation, or the atom bomb? At a far more mundane level could the surgeon-general in the midst of a 1930 Washington heat wave have anticipated that the now ubiquitous air-conditioner would be in common use only 20 years hence?

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