Fan Casing Noise Radiation

1991 ◽  
Vol 113 (1) ◽  
pp. 37-42 ◽  
Author(s):  
G. H. Koopmann ◽  
W. Neise ◽  
K. A. Cunefare
Keyword(s):  
Sound Pressure ◽  
Noise Spectrum ◽  
Centrifugal Fan ◽  
Noise Sources ◽  
Fan Noise ◽  
Noise Radiation ◽  
Starting Point ◽  
Element Program ◽  
Inlet Box ◽  
Subharmonic Frequency

This paper presents a method for assessing the extent of casing noise radiation of a centrifugal fan relative to the aeroacoustic sources associated with the inlet box of the fan. Central to the method is a boundary element program which is used to compute the acoustic pressures on the surfaces of the fan casing in terms of its surface vibration which in this case was measured experimentally. Data from an earlier experiment was used as the starting point for this study. Available data included sound pressure measurements near and away from the inlet box of the fan and vibration measurements over the casing of the fan. Noise from the outlet duct of the fan was purposely highly attenuated. Computations of sound pressure, intensity, and power indicated that, at the blade passing frequency (300 Hz), the aerodynamic sources generated near the entrance plane of the inlet box of the fan dominate the noise spectrum in the field. On the other hand, at the first subharmonic frequency of the blade tone (150 Hz), the sound power generated from the inlet box and fan casing are within 3 dB of each other. Thus, for effective noise control at this frequency, it would be necessary to include both noise sources in the overall treatment.

Two-step computational aeroacoustics approach for underhood cooling fan application

2021 ◽  
Vol 263 (3) ◽  
pp. 3615-3624
Author(s):  
Parag Chaudhari ◽  
Jose Magalhaes ◽  
Aparna Salunkhe
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Air Flow ◽  
Computational Aeroacoustics ◽  
Noise Sources ◽  
Fan Noise ◽  
Cooling Fan ◽  
Sound Pressure Levels ◽  
One Step

Aeroacoustic noise is one of the important characteristics of the fan design. Computational Aeroacoustics (CAA) can provide better design options without relying on physical prototypes and reduce the development time and cost. There are two ways of performing CAA analysis; one-step and two-step approach. In one-step CAA, air flow and acoustic analysis are carried out in a single software. In two-step approach, air flow and acoustic analysis are carried out in separate software. Two-step CAA approach can expedite the calculation process and can be implemented in larger and complex domain problems. For the work presented in this paper, a mockup of an underhood cooling fan was designed. The sound pressure levels were measured for different installation configurations. The sound pressure level for one of the configurations was calculated with two-step approach and compared with test data. The compressible fluid flow field was first computed in a commercially available computational fluid dynamics software. This flow field was imported in a separate software where fan noise sources were computed and further used to predict the sound pressure levels at various microphone locations. The results show an excellent correlation between test and simulation for both tonal and broadband components of the fan noise.

scholarly journals ON APPLICABILITY OF ADDITIVE TECHNOLOGY IN PRODUCING NOZZLES FOR JET NOISE INVESTIGATIONS

Akustika ◽  
2019 ◽  
Vol 34 ◽  
pp. 180-184 ◽  
Author(s):  
Igor Khramtsov ◽  
Evgeniya Cherenkova ◽  
Vadim Palchikovskiy ◽  
Oleg Kustov
Keyword(s):  
Sound Pressure ◽  
Small Diameter ◽  
Jet Noise ◽  
Additive Technology ◽  
Noise Radiation ◽  
Fused Deposition ◽  
Air Jet ◽  
Power Spectral ◽  
Noise Measurements ◽  
Jet Velocities

The split-type conical nozzles with replaceable exit sections with diameters of 30, 40 and 50 mm were designed and produced from steel by machine turning. In addition, the replaceable output parts of the nozzles with the same diameters were produced by additive technology (fused deposition manufacturing) from ABS plastic. In the acoustic anechoic chamber, the noise measurements of a single-stream cold air jet for all the nozzles at jet velocities in the range of 0.3-0.7 Mach numbers were carried out. The noise measurements were performed on distance of 2 m from the center of the nozzle exit section at angles from 30 to 105o. For different directions of noise radiation and different velocities of the jet, the power spectral density and overall sound pressure level were determined. The obtained results demonstrates that the jet noise for nozzles with diameter of 40 and 50 mm from steel and ABS plastic differs by no more than 1 dB, which is within the measurement error for these types of experiments. The nozzles with diameter 30 mm have a higher difference in noise, which can be explained by the more sensitivity of a nozzle with a small diameter to the deviations of geometric parameters when it produced by additive technology.

Effect of Pantograph and Bogie on Interior Noise of High-Speed Train in Tunnel

2013 ◽  
Vol 664 ◽  
pp. 191-196
Author(s):  
You Gang Xiao ◽  
Yu Shi
Keyword(s):  
High Speed ◽  
Sound Pressure ◽  
Broad Band ◽  
Pressure Level ◽  
Channel Noise ◽  
High Speed Train ◽  
Noise Sources ◽  
Vehicle Noise ◽  
Measurement And Analysis ◽  
Analysis System

For clarifying the noise in tunnel affected by pantograph and bogie, which are the most important noise sources, the noises near pantograph and bogie in a high-speed train were tested by multi-channel noise measurement and analysis system in tunnel, and compared with those measured outside the High-speed train and on an open field. The results show that the interior vehicle noise is spatially non-homogeneous in the whole carriage, the larger sound pressure level (SPL) near pantograph are next to ceiling, and near bogie next to floor. The noise spectra show a broad band feature, and dominated by the frequency contents among 100Hz-2kHz, so the countermeasures against noise should be within these range.

Effect of Rotor-Stator Configuration in the Generation of Vortical Scales and Wake Mixing in Single Stage Axial Fans: Part II — Assessment of Vortex Sound Sources

2013 ◽  
Author(s):  
Mónica Galdo Vega ◽  
Jesus Manuel Fernandez Oro ◽  
Katia María Argüelles Díaz ◽  
Carlos Santolaria Morros
Keyword(s):  
Deep Understanding ◽  
Operating Conditions ◽  
Axial Fan ◽  
Noise Sources ◽  
Sound Sources ◽  
Time Resolved ◽  
Vortex Sound ◽  
Starting Point ◽  
Axial Fans ◽  
The Impact

This second part is devoted to the identification of vortex sound sources in low-speed turbomachinery. As a starting point, the time-resolved evolution of the vortical motions associated to the wake shear layers (reported in the first part of the present study) is employed to obtain vorticity distributions in both blade-to-blade and traverse locations throughout the axial fan stage. Following, the Powell analogy for generation of vortex sound is revisited to obtain the noise sources in the nearfield region of the fan. Both numerical and experimental databases presented previously are now post-processed to achieve a deep understanding of the aeroacoustic behavior of the vortical scales present in the flow. A LES simulation at midspan, using a 2.5D scheme, allows an accurate description of the turn-out time of the shedding vortices, within high-density meshes in the blades and vanes passages, and a correct modeling of the dynamics of turbulence. Besides, thermal anemometry has been employed with a two-wire probe to measure the planar flow in the midspan sections of the fan. Statistical procedures and signal conditioning of velocity traces have confirmed experimentally the unsteady flow patterns devised in the numerical model. The comparison of the rotor-stator and the stator-rotor configurations provides the influence of the wake mixing and the nucleation of turbulent spots in the distribution of the Powell source terms. Moreover, the relation between the turbomachine configuration and the generation of vortex sound can be established, including the impact of the operating conditions and the contributions of the interaction mechanisms.

A Noise Assessment Framework for Subsonic Aircraft and Engines

2016 ◽  
Author(s):  
Fakhre Ali ◽  
Lars Ellbrant ◽  
David Elmdahl ◽  
Tomas Grönstedt
Keyword(s):  
Noise Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Civil Aviation ◽  
Assessment Framework ◽  
Component Level ◽  
Noise Sources ◽  
Total Noise ◽  
Engine Component ◽  
Noise Assessment

This paper proposes a preliminary subsonic aircraft and engine noise assessment framework, capable of computing the aircraft total noise level at all three certification points (i.e. Approach, Lateral, and Flyover) defined by the International Civil Aviation Organisation. The proposed framework is numerically integrated to account for the complete aircraft noise sources (i.e. the fuselage, wings, landing gear, as well as noise sources resulting from the engine component level, (i.e. fan, compressor, combustor, turbine, and jet). The developed framework is based on a wide-range of empirical and semi-empirical correlations collected from the public domain literature. The fidelity of the framework also caters for flight effects such as atmospheric attenuation, spherical spreading, Doppler shift, lateral attenuation, retarded time and ground reflection. A conversion between the sound pressure level SPL [SPLdB] to effective perceived noise level EPNL [EPNdB] is also included to allow for a consistent comparison with the certification procedure. Through the successful deployment of the proposed framework a generic aircraft model, representative of a modern commercial carrier aircraft has been investigated, operating under representative operational conditions. The sound pressure level corresponding to various aircraft and engine component have been thoroughly investigated and verified with trends acquired based on the theory. Furthermore, the predictions made by the framework corresponding to the aforementioned three certification points have also been verified against the noise level measurements provided by the International Civil Aviation Organization. The results acquired exhibit good correlation against the verification data for total noise levels at the microphones. Furthermore, a component level comparison is also presented which exhibit good agreement with verification data. The deployed methodology can essentially be regarded as an enabling technology to support the effective and efficient implementation of framework(s) (i.e. Technoeconomic, Environmental and Risk Assessment) targeted to evaluate the existing and advanced aircraft and engine architectures in terms of operational performance and environmental impact.

Sign in / Sign up

Export Citation Format

Share Document