Fan Compressor Noise Reduction

1969 ◽  
Author(s):  
M. J. Benzakein ◽  
S. B. Kazin
Keyword(s):  
Noise Reduction ◽  
Pure Tone ◽  
Potential Interaction ◽  
Row Spacing ◽  
Noise Generation ◽  
Analytical Treatment ◽  
Blade Row ◽  
Compressor Design ◽  
Reduction Methods ◽  
Aerodynamic Parameters

A study of various fan/compressor noise reduction methods is presented. The analytical treatment of the basic mechanisms of fan/compressor noise generation is described. The results are presented in parametric form and indicate the effects of fan/compressor design, number of blades, vane/blade ratio, aerodynamic parameters, and blade row spacing on pure tone noise reduction. These results are based on nonsteady aerodynamic treatment of wake and potential interaction effects and theoretical extensions of spinning mode theories.

scholarly journals On the Running Noise of Toothed Belt Drive : 2nd Report, Influence of Running Condition and Some Noise Reduction Methods

1971 ◽  
Vol 37 (293) ◽  
pp. 203-211
Author(s):  
Aizoh KUBO ◽  
Toshiaki ANDO ◽  
Susumu SATO ◽  
Toshio AIDA ◽  
Takeshi HOSHIRO
Keyword(s):  
Noise Reduction ◽  
Belt Drive ◽  
Toothed Belt ◽  
Reduction Methods

COMPARISON OF MONOPOLE AND DIPOLE NOISE REDUCTION METHODS

2020 ◽  
Vol 4 (67) ◽  
pp. 153-160
Author(s):  
Oleg I. Polivaev ◽  
◽  
Alexey N. Kuznetsov ◽  
Dmitriy Yu. Terekhov ◽  
Viktor V. Trufanov ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Reduction Methods

Noise Reduction During Acoustic Monitoring of Laser Welding of High-Strength Steels

2009 ◽  
Author(s):  
Wei Huang ◽  
Radovan Kovacevic
Keyword(s):  
Laser Welding ◽  
Noise Reduction ◽  
Acoustic Signal ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Weld Penetration ◽  
Acoustic Signatures ◽  
Reduction Methods ◽  
Laser Welding Process

During the laser welding process of high-strength steels, different defects, such as a partial weld penetration, spatters, and blow-through holes could be present. In order to detect the presence of defects and achieve a quality control, acoustic monitoring based on microphones is applied to the welding process. As an effective sensor to monitor the laser welding process, however, the microphone is greatly limited by intensive noise existing in the complex industrial environment. In this paper, in order to acquire a clean acoustic signal from the laser welding process, two noise reduction methods are proposed: one is the spectral subtraction method based on one microphone and the other one is the beamforming based on a microphone array. By applying these two noise reduction methods, the quality of the acoustic signal is enhanced, and the acoustic signatures are extracted both in the time domain and frequency domain. The analysis results show that the extracted acoustic signatures can well indicate the different weld penetration states and they can also be used to study the internal mechanisms of the laser-material interaction.

scholarly journals Improved Turbulence Profiling with Field-Adapted Acoustic Doppler Velocimeters Using a Bifrequency Doppler Noise Suppression Method

2008 ◽  
Vol 25 (3) ◽  
pp. 452-463 ◽  
Author(s):  
D. Hurther ◽  
U. Lemmin
Keyword(s):  
Noise Reduction ◽  
Carrier Frequency ◽  
Noise Suppression ◽  
Isotropic Turbulence ◽  
Field Studies ◽  
Sample Volume ◽  
Grid Turbulence ◽  
Electronic Circuitry ◽  
Reduction Methods ◽  
Velocity Spectra

Abstract A novel noise reduction method and corresponding technique are presented for improving turbulence measurements with acoustic Doppler velocimeters (ADVs) commonly used in field studies of coastal and nearshore regions, rivers, lakes, and estuaries. This bifrequency method is based on the decorrelation of the random and statistically independent Doppler noise terms contained in the Doppler signals at two frequencies. It is shown through experiments in an oscillating grid turbulence (OGT) tank producing diffusive isotropic turbulence that a shift in carrier frequency of less than 10% is sufficient to increase the resolved frequency range by a decade in the turbulent velocity spectra. Over this spectral range, the slope of the velocity spectra agrees well with the universal inertial range value of −5/3. The limit due to spatial averaging effects over the sample volume can be determined from the abrupt deviation of the spectral slope from the −5/3 value. As a result, the relative error of the turbulent intensity estimate and the turbulent kinetic energy (TKE) dissipation rate, measured by two different methods, does not exceed 10% in the case of isotropic turbulence. Furthermore, the bifrequency method allows accurate estimates of the turbulent microscales as shown by the good agreement of the ratio between the Taylor and Kolmogorov microscales and an Re1/4t power law. Compared to previous Doppler noise reduction methods (Garbini et al.), an increase in time resolution by a factor of 4 is achieved. The proposed method also avoids the loss of TKE energy contained in isotropic flow structures of size equal to and smaller than the sample volume. Different from Doppler noise methods proposed by Hurther and Lemmin and Blanckaert and Lemmin, this method does not require additional hardware components, electronic circuitry, or sensors because the redundant instantaneous velocity field information is captured with the same transducer. The required shift in carrier frequency is small enough for the bifrequency method to be easily implemented in commercial ADVs.

Discrete Frequency Noise Generation From an Axial Flow Fan Blade Row

1970 ◽  
Vol 92 (1) ◽  
pp. 37-43 ◽  
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.

scholarly journals Aeroacoustics of Silent Owl Flight

2020 ◽  
Vol 52 (1) ◽  
pp. 395-420 ◽  
Author(s):  
Justin W. Jaworski ◽  
N. Peake
Keyword(s):  
Mathematical Modeling ◽  
Noise Reduction ◽  
Current Knowledge ◽  
Foraging Strategies ◽  
Aerodynamic Noise ◽  
Noise Generation ◽  
Reduction Strategies ◽  
Noise Measurements ◽  
Modeling And Experiments ◽  
Review Current

The ability of some species of owl to fly in effective silence is unique among birds and provides a distinct hunting advantage, but it remains a mystery as to exactly what aspects of the owl and its flight are responsible for this dramatic noise reduction. Crucially, this mystery extends to how the flow physics may be leveraged to generate noise-reduction strategies for wider technological application. We review current knowledge of aerodynamic noise from owls, ranging from live owl noise measurements to mathematical modeling and experiments focused on how owls may disrupt the standard routes of noise generation. Specialized adaptations and foraging strategies are not uniform across all owl species: Some species may not have need for silent flight, or their evolutionary adaptations may not be effective for useful noise reduction for certain species. This hypothesis is examined using mathematical models and borne out where possible by noise measurements and morphological observations of owl feathers and wings.

A new methodology for preliminary design of centrifugal impellers with prewhirl

2019 ◽  
Vol 234 (3) ◽  
pp. 251-262 ◽  
Author(s):  
Xiaojian Li ◽  
Yijia Zhao ◽  
Zhengxian Liu ◽  
Hua Chen
Keyword(s):  
Centrifugal Compressor ◽  
Maximum Flow ◽  
High Flow ◽  
Centrifugal Impeller ◽  
Preliminary Design ◽  
Design Specification ◽  
Vaned Diffuser ◽  
Flow Capacity ◽  
Compressor Design ◽  
Aerodynamic Parameters

The overall trend of centrifugal compressor design is to strive for high aerodynamic performance and high flow capacity products. A new methodology is derived to implement a preliminary design for high flow capacity centrifugal impeller with and without prewhirl. First, several new non-dimensional equations connecting impeller geometric and aerodynamic parameters are derived for the maximum flow capacity. The effects of prewhirl on mass flow function, inlet diameter ratio and work coefficient are discussed, respectively. Then, based on these equations, a series of design diagrams are drawn to extract the universal rules in centrifugal impeller design with prewhirl. Some physical limits of design maps are also discussed. Finally, the throat area of impeller is discussed under prewhirl, and the matching principle between prewhirl impeller and vaned diffuser is derived and validated. The proposed method can be used to design a new centrifugal compressor, or to evaluate the design feasibility and the challenge of a given design specification.

On the Design Method of Noise Reduction of Centrifugal Fan

2012 ◽  
Vol 487 ◽  
pp. 520-524
Author(s):  
Li Xia Peng
Keyword(s):  
Noise Reduction ◽  
Reduction Method ◽  
Design Method ◽  
Noise Generation ◽  
Centrifugal Fan ◽  
Centrifugal Blower

The application of centrifugal fan is wide, but the huge noise can pollute the environment. This paper will discuss the mechanism of centrifugal blower noise generation, and put forward noise reduction method in designing centrifugal blower creatively, thus can solve the problems effectively.

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