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.

Estimating Jet Noise

1963 ◽  
Vol 14 (1) ◽  
pp. 1-16 ◽  
Author(s):  
G. M. Coles
Keyword(s):  
Sound Pressure ◽  
Jet Noise ◽  
Ground Level ◽  
Far Field ◽  
Performance Parameters ◽  
Noise Sources ◽  
Wide Range ◽  
Noise Measurements ◽  
Noise Assessment ◽  
Considerable Period

SummaryA large number of far-field jet noise measurements obtained over a considerable period of time are presented, correlated in such a manner that they may be used to provide a complete noise assessment for any jet of which the performance parameters are known. The data are presented in two sections, one dealing with the problem of a static source near ground level, the other dealing with the case of a source in flight.Much of the data was derived from Avon engine tests, but a wide range of other jet noise sources has also been encompassed. Comparisons are drawn which show good correlation to exist between the overall sound pressure levels produced by jets of all sizes. It appears also that even the spectra quoted, which are based only on Avon measurements, are valid over a fairly wide range of jet sizes and are not peculiar to the Avon engine.

scholarly journals Exhaust Noise Reduction by Application of Expanded Collecting System in Pneumatic Tools and Machines

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1592
Author(s):  
Dominik Gryboś ◽  
Jacek S. Leszczyński ◽  
Dorota Czopek ◽  
Jerzy Wiciak
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Acoustic Pressure ◽  
Pressure Level ◽  
Computational Results ◽  
Noise Measurements ◽  
Exhaust Noise ◽  
Collecting System

In this paper, we demonstrate how to reduce the noise level of expanded air from pneumatic tools. Instead of a muffler, we propose the expanded collecting system, where the air expands through the pneumatic tube and expansion collector. We have elaborated a mathematical model which illustrates the dynamics of the air flow, as well as the acoustic pressure at the end of the tube. The computational results were compared with experimental data to check the air dynamics and sound pressure. Moreover, the study presents the methodology of noise measurement generated in a pneumatic screwdriver in a quiet back room and on a window-fitting stand in a production hall. In addition, we have performed noise measurements for the pneumatic screwdriver and the pneumatic screwdriver on an industrial scale. These measurements prove the noise reduction of the pneumatic tools when the expanded collecting system is used. When the expanded collecting system was applied to the screwdriver, the measured Sound Pressure Level (SPL) decreased from 87 to 80 dB(A).

The Effect of Longitudinal Core Flow on Trailing Vortex Stability

2014 ◽  
Author(s):  
Amir Allaf-Akbari ◽  
A. Gordon L. Holloway ◽  
Joseph Hall
Keyword(s):  
Experimental Study ◽  
Velocity Field ◽  
Kinetic Energy ◽  
Vortex Core ◽  
Vortex Generator ◽  
Core Flow ◽  
Vortex Stability ◽  
Vorticity Distribution ◽  
Air Jet ◽  
Jet Velocities

The current experimental study investigates the effect of longitudinal core flow on the formation and structure of a trailing vortex. The vortex is generated using four airfoils connected to a central hub through which a jet flow is added to the vortex core. Time averaged vorticity, circumferential velocity, and turbulent kinetic energy are studied. The statistics of vortex wandering are identified and corrections applied to the vorticity distribution. The vortex generator used in this study was built on the basis of the design described by Beninati et al. [1]. It uses four NACA0012 airfoils connected to a central hub. The wings orientation can be adjusted such that each contributes to a strong trailing vortex on the center of the test section. The vortex generator also had the capability to deliver an air jet directed longitudinally through a hole in the hub at the joint of the airfoils. Tests were done without the jet and with the air jet at jet velocities of 10 and 20 m/s. Planar PIV was used to measure the velocity field in the vicinity of the vortex core. The measurements were taken at 3 chords behind the vortex generator.

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.

Noise Power Spectrum for Firecrackers

2011 ◽  
Vol 2 (1) ◽  
pp. 62-70 ◽  
Author(s):  
K. B. Patange ◽  
A. R. Khan ◽  
S. H. Behere ◽  
Y. H. Shaikh
Keyword(s):  
Sound Pressure ◽  
Impulsive Noise ◽  
Power Spectra ◽  
Noise Power ◽  
Human Beings ◽  
Noise Levels ◽  
Different Types ◽  
Noise Measurements ◽  
Pressure Peak ◽  
High Sound

Frequency of noise can affect human beings in different ways. The sound of firecrackers is a type of intensive impulsive noise, which is hazardous. In this paper, the noise produced by firecrackers during celebration festivals in Aurangabad (M.S.), India is measured. The noise is analyzed from the study of power spectra for different types of firecrackers. Noise measurements of firecrackers show that they produce high sound pressure peak levels at their characteristics frequencies. Plots of noise power versus frequency for different crackers are presented and the inferences are discussed. Typical firecracker peak noise levels are given.

Designing Clean Jet-Noise Facilities and Making Accurate Jet-Noise Measurements

2003 ◽  
Vol 2 (3) ◽  
pp. 371-412 ◽  
Author(s):  
K. K. Ahuja
Keyword(s):  
Frequency Response ◽  
Internal Noise ◽  
Jet Noise ◽  
Noise Spectrum ◽  
Full Scale ◽  
Research Facility ◽  
High Quality ◽  
Jet Engine ◽  
Noise Measurements ◽  
Noise Data

The main objective of this paper is to provide guidelines for designing and calibrating a high quality, static, jet-noise research facility and making high-quality jet noise measurements. Particular emphasis is placed on methodology for determining if internal noise is dominant in the jet noise spectrum. A section of this document is devoted to clarifying the terminology associated with microphone frequency response corrections and providing a step-wise description of other corrections that must be applied to the measured raw spectra before the jet noise data can be considered accurate and ready for use for extrapolation to full-scale jet engine 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.

The role of shear-layer instability waves in jet exhaust noise

1977 ◽  
Vol 80 (2) ◽  
pp. 321-367 ◽  
Author(s):  
C. J. Moore
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Broad Band ◽  
Jet Noise ◽  
Acoustic Power ◽  
Thermal Fluctuations ◽  
Excess Noise ◽  
Number Range ◽  
Instability Waves ◽  
Noise Measurements

Large-scale structures in the form of instability waves are an inherent part of a shearlayer mixing process. Such structures are shown to be present in an acoustically and aerodynamically well behaved jet even at high Mach numbers. They do not directly radiate significant acoustic power in a subsonic jet, but do govern the production of the turbulent fluctuations which radiate broad-band jet noise. Over the whole subsonic Mach number range, a significant increase in jet noise can be produced by exciting the shear layer with a fluctuating pressure at the nozzle of only 0·08 % of the jet dynamic head but with the correct Strouhal number. Such excitation by internal acoustic, aerodynamic or thermal fluctuations could explain the variability of jet noise measurements between different rigs and could also be responsible for some components of ‘excess’ noise.

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