scholarly journals Innovative passive multifrequency propeller device for noise and vibration reduction in turboprop fuselage

2018 ◽  
Vol 233 ◽  
pp. 00030 ◽  
Author(s):  
Angelo De Fenza ◽  
Maurizio Arena ◽  
Leonardo Lecce
Keyword(s):  
Noise Reduction ◽  
Tonal Noise ◽  
Research Activity ◽  
Noise Sources ◽  
Noise And Vibration ◽  
Aircraft Fuselage ◽  
Research Sector ◽  
Aeronautical Industry ◽  
Flight Regimes ◽  
Passive Noise

One of the main comfort issue affecting the passenger comfort into a turboprop aircraft fuselage is the propeller tonal noise and the related vibrations. It is well known that propeller rotation during flight generates the main noise sources, depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust and blades geometry. Thanks to the progress behind the control systems of the blades rotations, an innovative highly selective DVA has been conceived. The purpose of the research activity has been improving the performances of the standard passive tonal noise control system used for the BPF tuned noise and vibration attenuation in turboprop aircraft. Due to specific commercial need, the use of bi-tuned frequency can lead at a passive noise reduction at two RPM regimes. Generally, the turboprop aircrafts use only two RPM regimes: 100% at take-off, climb and approach, 86% during cruise, climb and descent. An innovative passive bi-tonal device capable to be tuned at two different frequencies in order to optimize the fuselage noise reduction at two different flight regimes (100% and 86%), has been designed and numerically verified. The functional effectiveness of the bi-frequential tuned device has been analysed by finite elements simulations on a linear beam, representative of the turboprop fuselage frame. The outcomes achieved within this activity encourage the advancement of this research sector, as a support to the needs of the turboprop aeronautical industry. According to the long experience gained by the research group, the proposed multifunctional concept can be a valid technology solution ready to be manufactured as well as validated in flight.

Quantification of aerodynamically induced noise and vibration-induced noise in a suction unit

2011 ◽  
Vol 225 (3) ◽  
pp. 617-624 ◽  
Author(s):  
J Prezelj ◽  
M Čudina
Keyword(s):  
Transfer Function ◽  
Noise Reduction ◽  
Noise Source ◽  
Operating Conditions ◽  
Frequency Range ◽  
Centrifugal Blower ◽  
Noise Sources ◽  
Noise And Vibration ◽  
Different Types ◽  
The Individual

Noise, generated by a centrifugal blower, can be divided according to its origin, into aerodynamically induced noise and vibration-induced noise. The contribution of the individual noise source to the total emitted noise is hard to determine, but it is crucial for the design of noise reduction measures. In order to reduce the noise of the centrifugal blower in a broad range of operating conditions, an identification of noise sources needs to be performed. An analysis of the most important noise origin in a centrifugal blower presented in this article was performed by measurements of the transfer function between noise and vibration, under different types of excitation. From the analyses one can conclude that the dominant noise source of a centrifugal blower can be attributed to the aerodynamically generated noise which exceeds the vibration-induced noise for more than 10 dB in a broad frequency range.

scholarly journals Turbomachinery Noise Predictions: Present and Future

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 92-116 ◽  
Author(s):  
Stéphane Moreau
Keyword(s):  
Hybrid Methods ◽  
Free Field ◽  
Broadband Noise ◽  
Large Eddy Simulations ◽  
Analytical Models ◽  
Flat Plates ◽  
Tonal Noise ◽  
Noise Sources ◽  
Large Eddy ◽  
Rans Simulations

In future Ultra-High By-Pass Ratio turboengines, the turbomachinery noise (fan and turbine stages mainly) is expected to increase significantly. A review of analytical models and numerical methods to yield both tonal and broadband contributions of such noise sources is presented. The former rely on hybrid methods coupling gust response over very thin flat plates of finite chord length, either isolated or in cascade, and acoustic analogies in free-field and in a duct. The latter yields tonal noise with unsteady Reynolds-Averaged Navier–Stokes (u-RANS) simulations, and broadband noise with Large Eddy Simulations (LES). The analytical models are shown to provide good and fast first sound estimates at pre-design stages, and to easily separate the different noise sources. The u-RANS simulations are now able to give accurate estimates of tonal noise of the most complex asymmetric, heterogeneous fan-Outlet Guiding Vane (OGV) configurations. Wall-modeled LES on rescaled stage configurations have now been achieved on all components: a low-pressure compressor stage, a transonic high-pressure turbine stage and a fan-OGV configuration with good overall sound power level predictions for the latter. In this case, hybrid Lattice–Boltzmann/very large-eddy simulations also appear to be an excellent alternative to yield both contributions accurately at once.

Untersuchung der Regelwerke für den passiven Schallschutz unter Berücksichtigung aktueller Verkehrslärmspektren – Teil 1

2020 ◽  
Vol 15 (01) ◽  
pp. 17-21
Author(s):  
J. Weinzierl ◽  
W. Wieland
Keyword(s):  
Correction Term ◽  
Spectral Composition ◽  
Sound Insulation ◽  
Assessment Procedure ◽  
Noise Sources ◽  
Frequency Dependent ◽  
Protection Goal ◽  
Passive Noise ◽  
Sound Reduction ◽  
Spectrum Adaptation

In den Regelwerken zum passiven Schallschutz von Umfassungsbauteilen wird das erforderliche Schalldämm-Maß der Fassade als Einzahlwert entsprechend dem Bewertungsverfahren nach DIN EN ISO 717-1 [1] ermittelt. Um die spektrale Zusammensetzung verschiedener Lärmquellen und die frequenzabhängige Schalldämmung von Fassadenbauteilen zu berücksichtigen, werden in den einschlägigen Regelwerken Korrektursummanden bzw. Spektrum-Anpassungswerte verwendet. Im folgenden Beitrag wird der Einfluss verschiedener Außenlärmspektren und frequenz- abhängiger Schalldämm-Maße auf den Innenpegel diskutiert. Insbesondere werden die Unterschiede zwischen Holz- und Massivbauweise bezüglich des Schutzziels bzw. des Innenpegels betrachtet. Die Untersuchungen zeigen, dass keine generelle Differenzierung zwischen Leicht- und Massivbauweise erforderlich ist. Für hochschalldämmende Leichtbaukonstruktionen mit einem Ctr,50–5000 < –8 dB wird jedoch ein Korrekturterm für das erforderliche Fassaden-Schalldämm-Maß zur Sicherstellung des Schutzziels vorgeschlagen. &nbsp; &nbsp; Summary In the regulations for passive noise protection of surrounding components, the required sound reduction index of the facade is determined as a single value according to the assessment procedure according to DIN EN ISO 717-1 [1]. In order to take into account the spectral composition of different noise sources and the frequency-dependent sound insulation of facade components, correction summands or spectrum adaptation values are used in the relevant regulations. The following article discusses the influence of various outside noise spectra and frequency-dependent sound insulation measures on the inside level. In particular, the differences between wood and solid construction were considered with regard to the protection goal and the internal level. The investigations show that no general differentiation between lightweight and solid construction is necessary. For highly sound-insulating lightweight constructions with a Ctr, 50–5000 <-8 dB, however, a correction term for the required facade soundproofing dimension to ensure the protection goal is proposed. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

Trailing-edge noise reduction of a wing by a surface modification

2021 ◽  
Vol 263 (3) ◽  
pp. 3194-3201
Author(s):  
Varun Bharadwaj Ananthan ◽  
R.A.D. Akkermans ◽  
Dragan Kozulovic
Keyword(s):  
Noise Reduction ◽  
Stochastic Approach ◽  
Slight Reduction ◽  
Noise Sources ◽  
Trailing Edge ◽  
Sound Sources ◽  
Airframe Noise ◽  
Trailing Edge Noise ◽  
Random Particle ◽  
Noise Production

There is an increased emphasis on reducing airframe noise in the last decades. Airframe noise is sound generated by the interaction of a turbulent flow with the aircraft geometry, and significantly contributes to the overall noise production during the landing phase. One examples of airframe noise is the noise generated at a wing's trailing edge, i.e., trailing-edge noise. In this contribution, we numerically explore the local application of riblets for the purpose of trailing-edge noise reduction. Two configurations are studied: i) a clean NACA0012 wing section as a reference, and ii) the same configuration with riblets installed at the wing's aft part. The numerical investigation follows a hybrid computational aeroacoustics approach, where the time-average flow is studied by means of RANS. Noise sources are generated by means of a stochastic approach called Fast Random Particle Mesh method. The results show a deceleration of the flow behind the riblets. Furthermore, the turbulent kinetic energy indicates increased unsteadiness behind the riblets which is shifted away from the wall due to the presence of the riblets. Lastly, the sound sources are investigated by means of the 3D Lamb-vector, which indicates a slight reduction in magnitude near the trailing edge.

Experimental study of wavy trailing edge serrations on flat rotor blades

2021 ◽  
Vol 263 (5) ◽  
pp. 1855-1866
Author(s):  
Sai Manikanta Kaja ◽  
K. Sriinivasan ◽  
A. Jaswanth Kalyan Kumar
Keyword(s):  
Experimental Study ◽  
Noise Reduction ◽  
Pitch Angle ◽  
Acoustic Emissions ◽  
Broadband Noise ◽  
Rotor Blades ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Low Speeds ◽  
Trailing Edge Serrations

A detailed experimental study is conducted to observe the effect of various parameters like wavelength, depth of serrations, and pitch angle on serrated blades' acoustic emissions at low speeds up to 2000 rpm. Experiments are conducted on flat blade rotors with sinusoidal serrations on the trailing edge of blades with different amplitudes and wavelengths. A total of 7 blades with different serration configurations, including a base configuration, are studied, five of them have serrations throughout the span of the blade, and one configuration has serration of varying amplitude on the farther half of the blade. It is observed that some blade configurations have resulted in tonal noise reduction noise as much as 8dB, whereas some of the serration configurations reduce very little to none, there is no significant effect of T.E serrations on the broadband noise emitted by the rotor. Directivity of noise generated from the rotor, the effect of serrations on the directivity of the noise is studied.

Radiation modes of propeller tonal noise

2021 ◽  
pp. 1-25
Author(s):  
Hanbo Jiang ◽  
Siyang Zhong ◽  
Han Wu ◽  
Xin Zhang ◽  
Xun Huang ◽  
...  
Keyword(s):  
Spherical Harmonics ◽  
Sound Field ◽  
Low Noise ◽  
Noise Model ◽  
Sound Waves ◽  
Tonal Noise ◽  
Noise Sources ◽  
Separate Source ◽  
Radial Forces ◽  
Flow Variables

Abstract This paper focuses on the radiation modes and efficiency of propeller tonal noise. The thickness noise and loading noise model of propellers has been formulated in spherical coordinates, thereby simplifying numerical evaluation of the integral noise source. More importantly, the radiation field can be decomposed and projected to spherical harmonics, which can separate source-observer positions and enable an analysis of sound field structures. Thanks to the parity of spherical harmonics, the proposed model can mathematically explain the fact that thrusts only produce antisymmetric sound waves with respect to the rotating plane. In addition, the symmetric components of the noise field can be attributed to the thickness, as well as drags and radial forces acting on the propeller surface. The radiation efficiency of each mode decays rapidly as noise sources approach the rotating centre, suggesting the radial distribution of aerodynamic loadings should be carefully designed for low-noise propellers. The noise prediction model has been successfully applied to a drone propeller and achieved a reliable agreement with experimental measurements. The flow variables employed as an input of the noise computation were obtained with computational fluid dynamics (CFD), and the experimental data were measured in an anechoic chamber.

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