Hot-Jet Noise Test of a Revised Notched Nozzle

2012 ◽  
Author(s):  
Tatsuya Ishii ◽  
Nozomi Tanaka ◽  
Hideshi Oinuma ◽  
Tsutomu Oishi
Keyword(s):  
Noise Reduction ◽  
Flow Rate ◽  
High Speed ◽  
Large Scale ◽  
Jet Noise ◽  
Outdoor Environment ◽  
Engine Test ◽  
Noise Component ◽  
Jet Mixing ◽  
Noise Test

Jet noise remains a significant noise component in modern commercial aero-engines. A high-speed flow mixing with the surrounding air constitutes noise sources behind the nozzle. One noise-reduction technology is a mixing device attached to the nozzle. Several fixed-geometry mixers such as chevrons have been studied by both computational and experimental approaches. The authors have previously proposed a notched nozzle with dents allocated along the nozzle lip and discussed its ability to reduce the noise level. The revised notch was expected to suppress the broadband jet-mixing noise as well as additional noise at higher frequencies. However, further assessments are required before proceeding to a large-scale engine test in an outdoor environment. First, the influence of the gas temperature on acoustic results must be tested because the temperature affects the mean jet velocity and sound propagation. As the preliminary noise test in the previous paper was limited to the cold-jet condition, far-field noise data under the hot-jet condition should be investigated. Second, the aerodynamic performance must be evaluated. Data on the flow rate and thrust would help in considering the aerodynamic performances between the baseline, notched, and chevron nozzles. This study focuses on noise tests for the finer-notched nozzle under the hot-gas condition. A small jet engine for model jet planes was employed to generate a high-temperature jet. An engine test stand was designed to monitor the engine performance data, consisting of the pressure and temperature at several positions, the fuel flow rate, and the thrust. The hot-jet test with and without the mixing device served as a compact and flexible test for aerodynamic evaluation of the nozzle. The noise test results under the hot-jet condition with this rig showed that the noise reduction characteristics of the finer-notched nozzle are different from those of conventional mixers.

Noise Test of Revised Notched Nozzle Using a Jet Engine

2013 ◽  
Author(s):  
Tatsuya Ishii ◽  
Nozomi Tanaka ◽  
Tsutomu Oishi ◽  
Yutaka Ishii
Keyword(s):  
Noise Reduction ◽  
Large Scale ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Outdoor Environment ◽  
Mixing Process ◽  
Cross Sectional ◽  
Additional Noise ◽  
Previous Design ◽  
Noise Test

This paper describes engine noise tests conducted in an outdoor environment using a revised notched nozzle. A notch is a small dent formed at the nozzle edge that penetrates into the primary jet. The notched nozzle is expected to improve the acoustic performance with less deterioration in aerodynamic performance relative to that of a conventional nozzle. The slight penetration of the notch causes small disturbances immediately after the nozzle, driving the subsequent mixing process in the shear layer. This mixing process helps suppress both large-scale vortices in the far downstream region and excessive shear stress near the nozzle. The authors have researched and developed various notched nozzles. Previous engine tests using a 6-notched nozzle showed that the notch itself caused additional noise by increasing the sound pressure level at higher frequencies. To counter this problem, a revised 18-notched nozzle was developed through computational and experimental studies. The authors’ previous paper [Ishii, et al.; ASME Paper GT2012-69507, 2012] showed that this nozzle increased the noise reduction toward the side direction of the nozzle under hot-jet conditions. However, there remain some unsolved issues. One issue is the scale of the nozzle. Another issue is the test conditions, such as the different effective cross-sectional areas. In this light, a larger-scale nozzle with a diameter five times larger than that in the hot-jet model was prepared so as to adjust the nozzle aerodynamic performance. Noise tests of this nozzle were carried out using a turbojet engine together with far-field and phased array microphones, and the revised notched nozzle was found to show improved noise reduction performance compared to the previous design.

Adaptation of the Beveled Nozzle for High-Speed Jet Noise Reduction

AIAA Journal ◽  
2011 ◽  
Vol 49 (5) ◽  
pp. 932-944 ◽  
Author(s):  
K. Viswanathan ◽  
M. J. Czech
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Jet Noise

High-Speed Jet Noise Reduction Using Microjets on a Jet Engine

2004 ◽  
Author(s):  
Brenton Greska ◽  
Anjaneyulu Krothapalli ◽  
Nathan Burnside ◽  
William Horne
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Jet Noise ◽  
Jet Engine

Simultaneous Noise and Performance Measurements for High-Speed Jet Noise Reduction Technologies

2009 ◽  
Author(s):  
Dean Long ◽  
Steven Martens
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Near Field ◽  
Jet Noise ◽  
Source Distribution ◽  
Test Facility ◽  
Wave Radiation ◽  
Far Field ◽  
Shock Cell ◽  
Field Noise

Model scale tests are conducted to assess the Noise/Performance trade for high speed jet noise reduction technologies. It is demonstrated that measuring the near field acoustic signature with a microphone array can be used to assess the far field noise using a procedure known as acoustic holography. The near field noise measurement is mathematically propagated producing an estimate of the noise level at the new location. Outward propagation produces an estimate of the far field noise. Propagation toward the jet axis produces the source distribution. Tests are conducted on convergent/divergent nozzles with three different area ratios, and several different chevron geometries. Noise is characterized by two independent processes: Shock cell noise radiating in the forward quadrant is produced when the nozzle is operated at non-ideally expanded conditions. Mach wave radiation propagates into the aft quadrant when the exhaust temperature is elevated. These results show good agreement with actual far field measurements from tests in the GE Cell 41 Acoustic Test Facility. Simultaneous performance measurement shows the change in thrust coefficient for different test conditions and configurations. Chevrons attached to the nozzle exit can reduce the noise by several dB at the expense of a minimal thrust loss.

Acoustics measurements of military-style supersonic beveled nozzle jets with interior corrugations

2016 ◽  
Vol 16 (1-2) ◽  
pp. 21-43 ◽  
Author(s):  
Russell W Powers ◽  
Dennis K McLaughlin
Keyword(s):  
Noise Reduction ◽  
Acoustic Field ◽  
High Speed ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Operating Conditions ◽  
Military Aircraft ◽  
Azimuthal Dependence ◽  
Penn State ◽  
Mixing Noise

Increasingly powerful and noisy military aircraft have generated the need for research leading to the development of supersonic jet noise reduction devices. The hot, high speed supersonic jets exhausting from military aircraft during takeoff present a most challenging problem. The present study extends prior research on two methods of noise reduction. The first is the internal nozzle corrugations pioneered by Seiner et al. and the second is the beveled exit plane explored most recently by Viswanathan. A novel research idea of creating fluidic corrugations similar to the nozzle corrugations has been initiated by Penn State. To further the understanding and analysis of the fluidic corrugations, the present study focuses on the flow field and acoustic field of nozzles with two, three, and six conventional, hardwalled corrugations. The effect of the combination of the internal corrugations with a beveled nozzle is explored. The results show that significant noise reductions of over 3 dB of the mixing noise and the broadband shock-associated noise can be achieved. The combination of the beveled nozzle and the internal nozzle corrugations showed that there is less azimuthal dependence of the acoustic field than for the purely beveled nozzle. The combination nozzle was shown to reduce the noise over a wider range of polar angles and operating conditions than either the purely beveled nozzle or the purely corrugated nozzle.

scholarly journals The sources of jet noise: experimental evidence

2008 ◽  
Vol 615 ◽  
pp. 253-292 ◽  
Author(s):  
CHRISTOPHER K. W. TAM ◽  
K. VISWANATHAN ◽  
K. K. AHUJA ◽  
J. PANDA
Keyword(s):  
High Speed ◽  
Noise Source ◽  
Jet Noise ◽  
Polar Angle ◽  
Sound Field ◽  
Source Distribution ◽  
Far Field ◽  
Noise Sources ◽  
Directional Information ◽  
Jet Mixing

The primary objective of this investigation is to determine experimentally the sources of jet mixing noise. In the present study, four different approaches are used. It is reasonable to assume that the characteristics of the noise sources are imprinted on their radiation fields. Under this assumption, it becomes possible to analyse the characteristics of the far-field sound and then infer back to the characteristics of the sources. The first approach is to make use of the spectral and directional information measured by a single microphone in the far field. A detailed analysis of a large collection of far-field noise data has been carried out. The purpose is to identify special characteristics that can be linked directly to those of the sources. The second approach is to measure the coherence of the sound field using two microphones. The autocorrelations and cross-correlations of these measurements offer not only valuable information on the spatial structure of the noise field in the radial and polar angle directions, but also on the sources inside the jet. The third approach involves measuring the correlation between turbulence fluctuations inside a jet and the radiated noise in the far field. This is the most direct and unambiguous way of identifying the sources of jet noise. In the fourth approach, a mirror microphone is used to measure the noise source distribution along the lengths of high-speed jets. Features and trends observed in noise source strength distributions are expected to shed light on the source mechanisms. It will be shown that all four types of data indicate clearly the existence of two distinct noise sources in jets. One source of noise is the fine-scale turbulence and the other source is the large turbulence structures of the jet flow. Some of the salient features of the sound field associated with the two noise sources are reported in this paper.

Prediction, Experiments and Optimization of High-Speed Jet Noise Reduction Using Fluidic Inserts

2014 ◽  
Author(s):  
Philip J. Morris ◽  
Dennis K. McLaughlin ◽  
Russell W. Powers ◽  
Matthew J. Kapusta
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Jet Noise

scholarly journals Mach-number scaling of individual azimuthal modes of subsonic co-flowing jets

2016 ◽  
Vol 793 ◽  
pp. 209-228 ◽  
Author(s):  
R. D. Sandberg ◽  
B. J. Tester
Keyword(s):  
Mach Number ◽  
Phased Array ◽  
Internal Noise ◽  
Jet Noise ◽  
Turbulent Jets ◽  
Noise Component ◽  
Axisymmetric Mode ◽  
Jet Mixing ◽  
Mixing Noise ◽  
The Individual

The Mach-number scaling of the individual azimuthal modes of jet mixing noise was studied for jets in flight conditions, i.e. with co-flow. The data were obtained via a series of direct numerical simulations (DNS), performed of fully turbulent jets with a target Reynolds number, based on nozzle diameter, of $Re_{jet}=8000$. The DNS included a pipe 25 diameters in length in order to ensure that the flow developed to a fully turbulent state before exiting into a laminar co-flow, and to account for all possible noise generation mechanisms. To allow for a detailed study of the jet mixing noise component of the combined pipe–jet configuration, acoustic liner boundary conditions on the inside of the pipe and a modification to the synthetic turbulent inlet boundary condition of the pipe were applied to minimize internal noise in the pipe. Despite these measures, the use of a phased-array source breakdown technique was essential in order to isolate the sources associated with jet noise mechanisms from additional noise sources that could be attributed to internal noise or unsteady flow past the nozzle lip, in particular for the axisymmetric mode. Decomposing the sound radiation from the pipe–jet configuration into its azimuthal Fourier modes, and accounting for the co-flow effects, it was found that at $90^{\circ }$ the individual azimuthal Fourier modes of far-field pressure for the jet mixing noise component exhibit the same $M^{8}$ scaling with the centreline jet Mach number as that experimentally documented for the overall noise field. Applying the phased-array source breakdown code to the DNS data at smaller angles to the jet axis, an increase of the velocity exponent of the jet noise source was found, approaching 10 at $30^{\circ }$. At this smaller angle the higher azimuthal modes again showed the same behaviour as the axisymmetric mode.

The generation of sound in turbulent motion

2008 ◽  
Vol 112 (1133) ◽  
pp. 381-394 ◽  
Author(s):  
G. M. Lilley
Keyword(s):  
Noise Reduction ◽  
Turbulent Flows ◽  
High Speed ◽  
Experimental Studies ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Aerodynamic Noise ◽  
Turbulent Shear ◽  
Noise Generation ◽  
Physical Mechanisms

Abstract The present paper reviews and discusses the physical mechanisms of noise generation and reduction in turbulent flows with their applications towards aircraft noise reduction at takeoff and on the approach. This work began in 1948 when Lilley undertook an experimental investigation into the source of jet noise as a necessary precursor to finding methods for the reduction of high speed jet engine noise on civil jet airliners. Westley and Lilley completed this experimental programme in 1951, which included the design of a range of devices for high speed jet noise reduction. It was about this time that similar studies on jet noise were being started elsewhere and in particular by Lassiter and Hubbard in USA. The major contribution to the subject of turbulence as a source of noise came from Sir James Lighthill’s remarkable theory in 1952. In spite of the difficulties attached to theoretical and experimental studies on noise from turbulence, it is shown that with the accumulated knowledge on aerodynamic noise over the past 50 years, together with an optimisation of aircraft operations including flight trajectories, we are today on the threshold of approaching the design of commercial aircraft with turbofan propulsion engines that will not be heard above the background noise of the airport at takeoff and landing beyond 1-2km, from the airport boundary fence. It is evident that in the application of this work, which centres on the physical mechanisms relating to the generation of noise from turbulence and turbulent shear flows, to jet noise, there is not one unique mechanism of jet noise generation for all jet Mach numbers. This author in this publication has concentrated on what appears to be the dominant mechanism of noise generation from turbulence, where the mean convection speeds of the turbulence are subsonic. The noise generated at transonic and supersonic jet speeds invariably involves extra mechanisms, which are only briefly referred to here.

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