scholarly journals Effect of a pylon on the broadband noise sources of counter-rotating turbomachinery

2021 ◽  
pp. 1475472X2110551
Author(s):  
Kristóf Tokaji ◽  
Csaba Horváth
Keyword(s):  
Noise Source ◽  
Microphone Array ◽  
Measurement Data ◽  
Leading Edge ◽  
Broadband Noise ◽  
Noise Sources ◽  
Noise Characteristics ◽  
Open Rotor ◽  
Blade Tip ◽  
Generation Mechanisms

Pylons are commonly used for the mounting of engines in the aircraft industry. On the other hand, the installation of a pylon influences the noise generation mechanisms and therefore alters the broadband noise characteristics of a given turbomachinery setup. In this investigation, a counter-rotating open rotor with and without a pylon is investigated in order to determine its effects on broadband noise sources. The various broadband noise sources and their typical frequency ranges have been determined using beamforming maps and spectral analysis. In order to attain a clear impression regarding the broadband noise sources, the Double Filtering beamforming method has been utilized in the investigation. This method removes the tonal components from the recorded signal of a microphone array, resulting in a purely broadband signal. Using beamforming maps, the dominant broadband noise source amplitudes and locations can therefore be investigated in great detail. Compared to other methods, the investigation of measurement data and beamforming maps helps determine the amplitude, the frequency range, and the significance of the various types of broadband noise sources that are truly present in the emitted noise. It has been found for lower frequencies, that the broadband noise sources at the blade root of the aft rotor are dominant, while for higher frequencies, the significant broadband noise sources are localized to the trailing edge region of the forward rotor and the leading edge of the aft rotor. The installation of a pylon has resulted in an additional broadband noise source appearing at the blade tip of the aft rotor.

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.

scholarly journals Source Contribution Analysis for Exterior Noise of a High-Speed Train: Experiments and Simulations

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Jie Zhang ◽  
Xinbiao Xiao ◽  
Dewei Wang ◽  
Yan Yang ◽  
Jing Fan
Keyword(s):  
High Speed ◽  
Noise Source ◽  
High Speed Train ◽  
Noise Sources ◽  
Sound Sources ◽  
Lower Region ◽  
Source Contribution ◽  
Array Measurements ◽  
Noise Characteristics ◽  
Train Speed

This paper presents a detailed investigation into the contributions of different sound sources to the exterior noise of a high-speed train both experimentally and by simulations. The in situ exterior noise measurements of the high-speed train, including pass-by noise and noise source identification, are carried out on a viaduct. Pass-by noise characteristics, noise source localizations, noise source contributions of different regions, and noise source vertical distributions are considered in the data analysis, and it is shown how they are affected by the train speed. An exterior noise simulation model of the high-speed train is established based on the method of ray acoustics, and the inputs come from the array measurements. The predicted results are generally in good agreement with the measurements. The results show that for the high-speed train investigated in this paper, the sources with the highest levels are located at bogie and pantograph regions. The contributions of the noise sources in the carbody region on the pass-by noise increase with an increasing distance, while those in the bogie and train head decrease. The source contribution rates of the bogie and the lower region decrease with increasing train speed, while those of the coach centre increase. At a distance of 25 m, the effect of the different sound sources control on the pass-by noise is analysed, namely, the lower region, bogie, coach centre, roof region, and pantograph. This study can provide a basis for exterior noise control of high-speed trains.

A Comparison of Frequency-Domain Microphone Array Methods for the Characterization of Rotating Broadband Noise Sources

2019 ◽  
Vol 105 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Christof Ocker ◽  
Gert Herold ◽  
Florian Krömer ◽  
Wolfram Pannert ◽  
Ennes Sarradj ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Microphone Array ◽  
Broadband Noise ◽  
Noise Sources

Noise assessment of taxibotted versus conventional taxiing operations using a phased microphone array

2021 ◽  
Vol 263 (5) ◽  
pp. 1152-1163
Author(s):  
Bieke von den Hoff ◽  
Mirjam Snellen ◽  
Dick G. Simons
Keyword(s):  
Noise Source ◽  
Microphone Array ◽  
Noise Levels ◽  
Noise Sources ◽  
Operational Testing ◽  
Electric Aircraft ◽  
Noise Source Identification ◽  
Noise Measurements ◽  
Noise Assessment ◽  
Lower Noise

In sustainable aviation the focus is mostly applied to the greenhouse gas emissions during flight. However airports have an increasing interest in reducing emissions during ground operations such as taxiing for example to improve the local air quality. Amsterdam Airport Schiphol started a pilot for sustainable taxiing with a pilot-controlled hybrid-electric aircraft towing vehicle called TaxiBot in 2020. The COVID-19 pandemic created an opportunity for extensive operational testing on a near-empty airport. Due to the low background noise levels in this situation, also a noise assessment of taxiing with the TaxiBot versus conventional two-engine taxiing was performed. This assessment can be used to evaluate the noise levels to which ground workers or neighbouring communities are exposed due to TaxiBot operations. For the noise measurements a phased microphone array was used, which allowed not only for a noise level and directionality assessment, but also for noise source identification. This paper compares the noise emissions and noise sources between a taxibotted and conventional taxiing operation. The results show that a taxibotted taxiing operation produces significantly lower noise levels. Additionally, acoustic imaging shows that the TaxiBot engine is the main noise source for a taxibotted pass-by manoeuvre.

Industrial Noise Source Identification by Using an Acoustic Beamforming System

1998 ◽  
Vol 120 (2) ◽  
pp. 426-433 ◽  
Author(s):  
M. R. Bai ◽  
J. Lee
Keyword(s):  
Source Identification ◽  
Noise Source ◽  
Microphone Array ◽  
Field Tests ◽  
Minimum Variance ◽  
Industrial Applications ◽  
Noise Sources ◽  
Multiple Signal Classification ◽  
Noise Source Identification ◽  
Identification Technique

A noise source identification technique is proposed for industrial applications by using a microphone array and beamforming algorithms. Both of the directions and the distances of long-range noise sources are calculated. The conventional method, the minimum variance (MV) method, and the multiple signal classification (MUSIC) method are the main beamforming algorithms employed in this study. The results of numerical simulations and field tests indicate the effectiveness of the acoustic beam-former in identifying noise sources in industrial environments.

An Aero-Acoustic Performance Prediction Method of Sirocco Fan

2010 ◽  
Author(s):  
Chan Lee ◽  
Hyun Gwon Kil
Keyword(s):  
Thickness Distribution ◽  
Cutoff Frequency ◽  
Prediction Method ◽  
Logarithmic Spiral ◽  
Aerodynamic Performance ◽  
Broadband Noise ◽  
Noise Sources ◽  
Fan Noise ◽  
Noise Characteristics ◽  
Sirocco Fan

A design-analysis method of Sirocco fan is developed for constructing 3-D impeller and scroll geometries, and for predicting both the aerodynamic performance and the noise characteristics of the designed fan. The aerodynamic blading design of fan is conducted by blade angle, camber line determinations and airfoil thickness distribution, and then the scroll geometry of fan is designed by using logarithmic spiral. The aerodynamic performance of designed fan is predicted by the mean line analysis with flow blockage, slip and pressure loss correlations. Based on the predicted performance data, fan noise is predicted by two models for cutoff frequency and broadband noise sources. The present predictions for the performance and the noise level of actual fans are well agreed with measurement results.

Effects of Vortex Generating Tabs on Noise Sources in an Ideally Expanded Mach 1.3 Jet

2003 ◽  
Vol 2 (1) ◽  
pp. 35-63 ◽  
Author(s):  
J. Hileman ◽  
M. Samimy
Keyword(s):  
Flow Visualization ◽  
Microphone Array ◽  
Pressure Ratio ◽  
Mixing Layer ◽  
Power Spectra ◽  
Acoustic Fields ◽  
Streamwise Vortices ◽  
Noise Sources ◽  
Noise Measurements ◽  
Generation Mechanisms

The flow and acoustic fields of an ideally expanded Mach 1.3 axisymmetric jet with delta tabs were examined to explore the effects of the tabs on noise sources. This work continues research that was performed on a baseline (no-tab) jet. Noise measurements were made at an angle of 30° to the downstream jet axis to allow a direct comparison to previous work, and to relate the sound generation mechanisms to the large structures that were visualized with temporally resolved flow visualization. Additional acoustic measurements were made at 60° and 90° locations. Three cases were examined: a baseline jet, a single delta tab jet, and a dual delta tab jet. Both tab jets were operated at the same pressure ratio as the baseline jet, which was ideally expanded. Power spectra and average acoustic waveform measurements were made for a variety of azimuthal locations; apparent noise origins were estimated with a 3-D microphone array; and temporally resolved flow visualization was used to examine the dynamic flow structure of the jet's mixing-layer. The results confirm that the tabs generate strong streamwise vortices that have a significant effect on both the flow and acoustic fields of the jet. The tabs cause significant deformation in the cross-stream plane of the mixing-layer, as well as regulating the formation and roll-up of vortices due to Kelvin Helmholtz instability. With the addition of tabs, the noise field becomes azimuthally dependent and the region of noise generation moves dramatically upstream. It appears that the tabs are directly responsible for an increase in noise over a range of Strouhal numbers between 0.8 and 2.5 through generated streamwise vortices and they are indirectly responsible for the modification of the noise generating mechanisms at Strouhal numbers below 0.6 through the induced spanwise vortex roll-ups.

scholarly journals Development of a Linear Acoustic Array for Aero-Acoustic Quantification of Camber-Bladed Vertical Axis Wind Turbine

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5954
Author(s):  
Abdul Hadi Butt ◽  
Bilal Akbar ◽  
Jawad Aslam ◽  
Naveed Akram ◽  
Manzoore Elahi M Soudagar ◽  
...  
Keyword(s):  
Microphone Array ◽  
Vertical Axis ◽  
Broadband Noise ◽  
Optimization Techniques ◽  
Small Radius ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Noise Characteristics ◽  
Acoustic Quantification ◽  
Trailing Edge Serrations

Vertical axis wind turbines (VAWT) are a source of renewable energy and are used for both industrial and domestic purposes. The study of noise characteristics of a VAWT is an important performance parameter for the turbine. This study focuses on the development of a linear microphone array and measuring acoustic signals on a cambered five-bladed 45 W VAWT in an anechoic chamber at different tip speed ratios. The sound pressure level spectrum of VAWT shows that tonal noises such as blade passing frequencies dominate at lower frequencies whereas broadband noise corresponds to all audible ranges of frequencies. This study shows that the major portion of noise from the source is dominated by aerodynamic noises generated due to vortex generation and trailing edge serrations. The research also predicts that dynamic stall is evident in the lower Tip speed ratio (TSR) region making smaller TSR values unsuitable for a quiet VAWT. This paper compares the results of linear aeroacoustic array with a 128-MEMS acoustic camera with higher resolution. The study depicts a 3 dB margin between two systems at lower TSR values. The research approves the usage of the 8 mic linear array for small radius rotary machinery considering the results comparison with a NORSONIC camera and its resolution. These observations serve as a basis for noise reduction and blade optimization techniques.

Sign in / Sign up

Export Citation Format

Share Document