Single-Stream Jet Noise Prediction Using Empirical Methodology for a Newly Designed Turbojet Engine

2013 ◽  
Author(s):  
João Roberto Barbosa ◽  
Daniel Jonas Dezan
Keyword(s):  
Sound Pressure Level ◽  
Performance Prediction ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Jet Noise ◽  
Pressure Level ◽  
High Fidelity ◽  
Noise Prediction ◽  
Single Stream ◽  
Turbojet Engine

The Center for Reference on Gas Turbines (CRTG), at the Technological Institute of Aeronautics, carries out research in relevant areas of gas turbines, to provide the support for teaching and the ability to design high performance gas turbines. Noise prediction, by means of theoretical and empirical methods, is among such areas. Emphasis is given to the prediction of noise from new engines, to anticipate problems at very early design stage and to take the necessary actions to guarantee that the engine noise is below the recommended limits. Noise prediction is part of a high fidelity gas turbine performance prediction computer program, which provides the designer, at any time during the design phases, with information on the noise levels generated by each component and by the engine. This paper presents results obtained with such methodology incorporated to the high fidelity engine performance prediction computer code, and in the format usually used in the literature. The SPL — far-field one-third octave band sound pressure level — and the OASPL — overall sound pressure level — for single-stream jet were calculated for several engine rotational speeds and observer positions. Two methods have been for the single-stream jet noise prediction, namely: ESDU item 98019 and SAE ARP 876D. Nozzle details were taken from a 5 kN turbojet engine, designed at the CRTG, and which is being installed in the test rig for the preliminary evaluation. In this paper the influence of the observer position on the calculated SPL is presented, and the corresponding OASPL for steady engine operation, combined with the effect of the engine rotational speeds on exhaust jet noise. It is shown that they are in agreement with the noise of similar operating conditions. Ground reflection and atmospheric attenuation were not considered in this work. The results indicate that the noise prediction is adequate for use during the design phase and that the model derived in the SAE ARP 876D paper provides better single-stream jet noise prediction than ones predicted using the ESDU Item 98019.

Combustor and Single-Stream Jet Noise Prediction for a Newly Designed Turbojet Engine by Using Semi-Empirical Methods

2012 ◽  
Author(s):  
João Roberto Barbosa ◽  
Daniel Jonas Dezan
Keyword(s):  
Performance Prediction ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Engine Performance ◽  
Design Stage ◽  
High Fidelity ◽  
Noise Prediction ◽  
Empirical Methods ◽  
Engine Noise ◽  
Turbojet Engine

Research is being carried out at the Technological Institute of Aeronautics to provide the support for the design of high performance gas turbines, including noise prediction by means of theoretical and empirical methods. Emphasis is given to new engines noise prediction, to anticipate problems at very early design stage and to take the necessary actions to guarantee that the engine noise is below the imposed limits. Noise prediction is part of the high fidelity engine performance prediction computer program, which provides the designer, at any time during the design phases, with information on the noise levels generated by each component and by the engine. Research indicates that the combustor and the propelling nozzle are major noise sources, so that these two components of a turbojet engine were dealt with in this work. The far-field one-third octave band sound pressure levels, (SPL), and overall sound pressure level (OASPL) are calculated, for several observer positions and engine rotational speeds. A 5 kN turbojet engine under development serves as the basis for the noise prediction. The influence of the observer position on SPL and OASPL for steady engine operation, as well as the effect of the engine rotational speeds on the engine noise generated by the combustor and the propelling nozzle are presented, which are in agreement with the noise of similar engines. Ground reflection and atmospheric attenuation were not considered. A high fidelity engine performance prediction computer code incorporates the noise prediction methodology whose results are reported in this paper.

Asymptotic properties of the overall sound pressure level of subsonic jet flows using isotropy as a paradigm

2010 ◽  
Vol 664 ◽  
pp. 510-539 ◽  
Author(s):  
M. Z. AFSAR
Keyword(s):  
Reynolds Stress ◽  
Sound Pressure Level ◽  
Small Angle ◽  
Sound Pressure ◽  
Asymptotic Properties ◽  
Jet Noise ◽  
Pressure Level ◽  
Mean Flow ◽  
The Mean ◽  
Jet Axis

Measurements of subsonic air jets show that the peak noise usually occurs when observations are made at small angles to the jet axis. In this paper, we develop further understanding of the mathematical properties of this peak noise by analysing the properties of the overall sound pressure level with an acoustic analogy using isotropy as a paradigm for the turbulence. The analogy is based upon the hyperbolic conservation form of the Euler equations derived by Goldstein (Intl J. Aeroacoust., vol. 1, 2002, p. 1). The mean flow and the turbulence properties are defined by a Reynolds-averaged Navier–Stokes calculation, and we use Green's function based upon a parallel mean flow approximation. Our analysis in this paper shows that the jet noise spectrum can, in fact, be thought of as being composed of two terms, one that is significant at large observation angles and a second term that is especially dominant at small observation angles to the jet axis. This second term can account for the experimentally observed peak jet noise (Lush, J. Fluid Mech., vol. 46, 1971, p. 477) and was first identified by Goldstein (J. Fluid Mech., vol. 70, 1975, p. 595). We discuss the low-frequency asymptotic properties of this second term in order to understand its directional behaviour; we show, for example, that the sound power of this term is proportional to the square of the mean velocity gradient. We also show that this small-angle shear term does not exist if the instantaneous Reynolds stress source strength in the momentum equation itself is assumed to be isotropic for any value of time (as was done previously by Morris & Farrasat, AIAA J., vol. 40, 2002, p. 356). However, it will be significant if the auto-covariance of the Reynolds stress source, when integrated over the vector separation, is taken to be isotropic in all of its tensor suffixes. Although the analysis shows that the sound pressure of this small-angle shear term is sensitive to the statistical properties of the turbulence, this work provides a foundation for a mathematical description of the two-source model of jet noise.

scholarly journals Noise-silencing technology for upright venting pipe jet noise

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879481 ◽  
Author(s):  
Enbin Liu ◽  
Shanbi Peng ◽  
Tiaowei Yang
Keyword(s):  
Natural Gas ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Jet Noise ◽  
Pressure Level ◽  
Living Environment ◽  
Frequency Noise ◽  
Frequency Range ◽  
Expansion Chamber

When a natural gas transmission and distribution station performs a planned or emergency venting operation, the jet noise produced by the natural gas venting pipe can have an intensity as high as 110 dB, thereby severely affecting the production and living environment. Jet noise produced by venting pipes is a type of aerodynamic noise. This study investigates the mechanism that produces the jet noise and the radiative characteristics of jet noise using a computational fluid dynamics method that combines large eddy simulation with the Ffowcs Williams–Hawkings acoustic analogy theory. The analysis results show that the sound pressure level of jet noise is relatively high, with a maximum level of 115 dB in the low-frequency range (0–1000 Hz), and the sound pressure level is approximately the average level in the frequency range of 1000–4000 Hz. In addition, the maximum and average sound pressure levels of the noise at the same monitoring point both slightly decrease, and the frequency of the occurrence of a maximum sound pressure level decreases as the Mach number at the outlet of the venting pipe increases. An increase in the flow rate can result in a shift from low-frequency to high-frequency noise. Subsequently, this study includes a design of an expansion-chamber muffler that reduces the jet noise produced by venting pipes and an analysis of its effectiveness in reducing noise. The results show that the expansion-chamber muffler designed in this study can effectively reduce jet noise by 10–40 dB and, thus, achieve effective noise prevention and control.

On the Performance of Porous Sound Absorbent Ceramic Lining in a Combustion Chamber Test Rig

2013 ◽  
Author(s):  
Hans-Christoph Ries ◽  
Mateus Vieira Carlesso ◽  
Christian Eigenbrod ◽  
Stephen Kroll ◽  
Kurosch Rezwan
Keyword(s):  
Combustion Chamber ◽  
Sound Pressure Level ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Porous Ceramic ◽  
Pressure Level ◽  
Test Rig ◽  
Resonance Frequencies ◽  
Lean Premixed ◽  
Ceramic Lining

This paper discusses the potential of using porous ceramic lining as insulating material in combustion chambers with respect to their sound absorbent ability to suppress thermoacoustic instabilities. For this purpose a combustion chamber test rig was developed and different types of ceramic linings were tested. The examined range of power was between 40 and 250 kW and the air-propane equivalence ratio was between 1.2 and 2.0. The overall sound pressure level and frequency domain of a lean premixed swirl stabilized and piloted burner are presented. The resonance frequencies and sound pressure levels are obtained and compared for the different combustion chamber linings. The results show a significant decrease in overall sound pressure level by up to 23.5 dB for sound absorbent lining in comparison to the common sound reflecting combustion chamber lining. In summary, sound absorbent ceramic combustion chamber lining can contribute to improve the stability of lean premixed gas turbines.

Innovation in Noise Mapping in Natural Gas Compressor Stations

2010 ◽  
Author(s):  
K. K. Botros ◽  
A. Hawryluk ◽  
J. Geerligs ◽  
B. Huynh ◽  
R. Phernambucq
Keyword(s):  
Sound Pressure Level ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Dominant Frequency ◽  
Pressure Level ◽  
Multiple Point ◽  
Noise Sources ◽  
Noise Mapping ◽  
Noise Measurements ◽  
Future Work

Noise is generated at gas turbine-based compressor stations from a number of sources, including turbomachinery (gas turbines and compressors), airflow through inlet ducts and scrubbers, exhaust stacks, aerial coolers, and auxiliary systems. Understanding these noise sources is necessary to ensure that the working conditions on site are safe and that the audible noise at neighbouring properties is acceptable. Each noise source has different frequency content, and the overall sound pressure level (OSPL) at any location in the station yard or inside the compressor building is the result of a superposition of these noise sources. This paper presents results of multiple-point spectral noise measurements at three of TransCanada’s compressor stations on the Alberta System. A method is described to determine the overall noise map of the station yard using Delaunay Triangulation and Natural-Neighbour Interpolation techniques. The results are presented in OSPL maps, as well as animated pictures of the sound pressure level (SPL) in frequency domain which will be shown on a video at the conference. The latter will be useful in future work to determine the culprit sources and the respective dominant frequency range that contributes the most to the OSPL.

Experimental Study on a Notched Nozzle for Jet Noise Reduction

2011 ◽  
Author(s):  
T. Ishii ◽  
H. Oinuma ◽  
K. Nagai ◽  
N. Tanaka ◽  
Y. Oba ◽  
...  
Keyword(s):  
Experimental Study ◽  
Noise Reduction ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Mixing Layer ◽  
Jet Noise ◽  
Computational Prediction ◽  
Pressure Level ◽  
Far Field ◽  
Noise Sources

This paper describes an experimental study on a notched nozzle for jet noise reduction. The notch, a tiny tetrahedral dent formed at the edge of a nozzle, is expected to enhance mixing within a limited region downstream of the nozzle. The enhanced mixing leads to the suppression of broadband peak components of jet noise with little effect on the engine performance. To investigate the noise reduction performances of a six-notch nozzle, a series of experiments have been performed at an outdoor test site. Tests on the engine include acoustic measurement in the far field to evaluate the noise reduction level with and without the notched nozzle, and pressure measurement near the jet plume to obtain information on noise sources. The far-field measurement indicated the noise reduction by as much as 3 dB in terms of overall sound pressure level in the rear direction of the engine. The use of the six-notch nozzle though decreased the noise-benefit in the side direction. Experimental data indicate that the high-frequency components deteriorate the noise reduction performance at wider angles of radiation. Although the increase in noise is partly because of the increase in velocity, the penetration of the notches into the jet plume is attributed to the increase in sound pressure level in higher frequencies. The results of near-field measurement suggest that an additional sound source appears up to x/D = 4 due to the notches. In addition, the total pressure maps downstream of the nozzle edge, obtained using a pressure rake, show that the notched nozzle deforms the shape of the mixing layer, causing it to become wavy within a limited distance from the nozzle. This deformation of the mixing layer implies strong vortex shedding and thus additional noise sources. To improve the noise characteristics, we proposed a revised version of the nozzle on the basis of a computational prediction, which contained 18 notches that were smaller than those in the 6-notched nozzle. Ongoing tests indicate greater noise reduction in agreement with the computational prediction.

Turbojet Engine Noise Prediction Utilizing Empirical Methods

2013 ◽  
Author(s):  
João Roberto Barbosa ◽  
Daniel Jonas Dezan
Keyword(s):  
Gas Turbines ◽  
Sound Pressure ◽  
Noise Prediction ◽  
Octave Band ◽  
Empirical Methods ◽  
Engine Noise ◽  
Noise Sources ◽  
Turbojet Engine ◽  
Sound Pressure Levels ◽  
The One

This work deals with the prediction of noise generated by gas turbines, which includes engines being designed. One has in mind the fulfillment of the ever-increasing concerns with environment, in particular noise. Analytical and empirical methods have been focused by researchers and industry, although only empirical prediction methods are utilized in this work, for the calculation of the one-third octave band sound pressure levels associated to the main engine noise sources. The methodology for the calculation of the engine noise has been combined with performance and design computational programs to evaluate the noise emitted by each engine component and, by proper combination, the engine total noise. A newly designed and manufactured 5 kN/1.2 MW turbojet engine serves as the basis for the noise prediction. For the study, the main noise sources are: compressor, combustor, turbine and propelling nozzle. In terms of the overall sound pressure level, OASPL, are compatible with the noise produced by similar engines. The noise predictions are performed at engine design speeds in the range of 100% down to 70% of the design speed (28,150 rpm). The engine has not run yet, but it is expected that measured noise will be available in the near future. However, it is important to emphasize that all prediction models used to evaluate the radiated noise from the engine were validated. The engine operating conditions were calculated using a high fidelity engine simulator developed to provide the data used in this study. The methods to estimate the one-third octave band sound pressure levels are reported in NASA TM-195480, SAE ARP-876D, NASA-ANOPP and ESDU Item 98019. No atmospheric attenuation and ground reflection were considered in this work.

A Study of Noise Generation on the E387, S823, NACA 0012, and NACA 4412 Airfoils for Use on Small-Scale Wind Turbines in the Urban Environment

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Kenneth W. Van Treuren ◽  
Andrew W. Hays
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Reynolds Numbers ◽  
Pressure Level ◽  
Small Scale ◽  
Noise Prediction ◽  
Noise Generation ◽  
Naca 0012

Four airfoils typical to small-scale wind turbines were studied for noise generation: Eppler 387, NREL S823, NACA 0012, and NACA 4412. Wind tunnel sound pressure level (SPL) data were collected directly downstream of the airfoil for angles of attack from −10 deg to 25 deg and for Reynolds numbers from 50,000 to 200,000. Vertical and horizontal wake traverses define the extent of the noise generated. The data were analyzed by frequency and compared with a noise prediction from NREL AirFoil Noise (NAFNoise). The noise trends found can be applied to improve other airfoil selection when designing small-scale wind turbines.

Multi-objective design optimization of a high efficiency and low noise blower unit of a car air-conditioner

2019 ◽  
Vol 233 (13) ◽  
pp. 3493-3503 ◽  
Author(s):  
Masaru Kamada ◽  
Koji Shimoyama ◽  
Fumito Sato ◽  
Junya Washiashi ◽  
Yasufumi Konishi
Keyword(s):  
Genetic Algorithm ◽  
Design Optimization ◽  
Sound Pressure Level ◽  
Total Pressure ◽  
Sound Pressure ◽  
Low Noise ◽  
Pressure Level ◽  
Dynamics Simulation ◽  
Noise Prediction ◽  
Air Conditioners

Car air-conditioners consist of a blower unit and a heater unit. A blower unit sends wind to a heater unit, and a heater unit adjusts the temperature inside the vehicle. Blower units of car air-conditioners are required to be smaller, lighter, noiseless, and power-saving. However, it is difficult and expensive to predict the noise directly by computational fluid dynamics simulation. Hereupon, this study employs an indirect noise prediction method based on a noise prediction theory to evaluate noise for blower units inexpensively. This method is investigated through a comparison with actual sound pressure level measurement. Then, using this method, this study moves to design optimization of a blower unit of car air-conditioners. The optimization aims to improve total pressure efficiency and sound pressure level from the current design that has been employed for a real commercial vehicle. This study employs a genetic algorithm to explore global optima in a two-objective problem. The present genetic algorithm is assisted by the Kriging surrogate model to reduce computational cost required for evaluating objective functions. The optimization results indicate that the optimized blower unit involves a multi-blade fan with the high chord-pitch ratio to decrease the loss of total pressure efficiency, which is often induced by the flow separation on the blade and the swirling flow on the meridional plane. In addition, the sound pressure level of blower unit can be reduced by decreasing the local flow velocity on the meridian plane due to a blockage factor. A blower unit, which has a scroll with a large tongue angle, shows high total pressure efficiency because the increase in eddy loss is suppressed at the tongue. They suggest the importance of the matching of multi-blade fan and scroll to achieve the good overall performance of a blower unit.

Contributions of Voice and Nonverbal Communication to Perceived Masculinity–Femininity for Cisgender and Transgender Communicators

2020 ◽  
Vol 63 (4) ◽  
pp. 931-947
Author(s):  
Teresa L. D. Hardy ◽  
Carol A. Boliek ◽  
Daniel Aalto ◽  
Justin Lewicke ◽  
Kristopher Wells ◽  
...  
Keyword(s):  
Fundamental Frequency ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Vocal Tract ◽  
Presentation Mode ◽  
Pressure Level ◽  
Presentation Modes ◽  
Audiovisual Stimuli ◽  
Vocal Tract Resonance ◽  
Point Light

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity–femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women ( n = 10 of each) and transgender women ( n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers ( n = 20) rated each communicator's masculinity–femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity–femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity–femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

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