Jet noise shielding provided by a hybrid wing body aircraft

One approach toward achieving NASA's aggressive N+2 noise goal of 42 EPNdB cumulative margin below Stage 4 is through the use of novel vehicle configurations like the hybrid wing body. Jet noise measurements from a hybrid wing body acoustic test in the NASA Langley 14- by 22-Foot Subsonic Tunnel are described. Two dual-stream, heated Compact Jet Engine Simulator units are mounted underneath the inverted hybrid wing body model on a traversable support to permit measurement of varying levels of shielding provided by the fuselage. Both an axisymmetric and low noise chevron nozzle set are investigated in the context of shielding. The unshielded chevron nozzle set shows 1–2 dB of source noise reduction (relative to the unshielded axisymmetric nozzle set) with some penalties at higher frequencies. Shielding of the axisymmetric nozzles shows up to 6.5 dB of reduction at high frequency. The combination of shielding and low noise chevrons shows benefits beyond the expected additive benefits of the two, up to 10 dB, due to the effective migration of the jet source peak noise location upstream for increased shielding effectiveness. Jet noise source maps from phased array results processed with the deconvolution approach for the mapping of acoustic sources algorithm reinforce these observations.

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

International Journal of Aeroacoustics ◽

10.1260/147547203322986188 ◽

2003 ◽

Vol 2 (3) ◽

pp. 371-412 ◽

Cited By ~ 31

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.

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Experimental and Computational Approach for Jet Noise Mitigation by Mixing Control Devices

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Wind Turbine Technology ◽

10.1115/gt2011-45200 ◽

2011 ◽

Cited By ~ 3

Author(s):

Nozomi Tanaka ◽

Tsutomu Oishi ◽

Yoshinori Ooba ◽

Shunji Enomoto ◽

Kazuomi Yamamoto ◽

...

Keyword(s):

Mach Number ◽

Shear Layer ◽

Nozzle Exit ◽

High Frequency ◽

Nozzle Design ◽

Noise Mitigation ◽

Eddy Simulation ◽

Large Eddy ◽

Noise Measurements ◽

Chevron Nozzle

The notched nozzle as a new concept has been investigated for conventional nozzle design together with the Chevron nozzle and Micro-jets, through feasibility studies. The notched nozzle has a plurality of triangular pyramid-shaped dent positioned in a circumferential direction along the nozzle exit. These studies include acoustic experiments that utilize a lab-scale simple model in an anechoic chamber and numerical approaches. The results of the Large Eddy Simulation are compared with the results of either acoustic or aerodynamic experiments. The objective of these investigations is to verify the effects of noise mitigation and to gain understanding of the physics of fluid dynamics around the nozzle exit, especially within the shear layer between high velocity jet flow and external flow/or ambient air. One concept of conventional noise mitigation devices involves mixing enhancements in the shear layer, but this sometimes produces high frequency self noise. Moreover it will result in a penalty in terms of thrust loss, additional weight and extra manufacturing cost due to the complicated shapes around the nozzle exit. It is difficult to produce a nozzle design without affecting high frequency self-noise and decreasing low-frequency noise towards to down stream of the jet engines even though there is no thrust loss. Most of this study, the experimental data were physically validated by three kinds of nozzle concepts designed to be equal to the conventional model in terms of size of nozzle exit diameter and Mach number. Essentially far-fields noise measurements and pressure measurements are conducted by polar angle microphones and arch-shaped pitot tubes are located downstream of the jet. The noise benefit which is produced by the notched nozzle as a lab-scale in far-fields noise measurements is up to 1.3dB at the side of the jet and 0.5dB at downstream, in terms of size of small-engine. Furthermore this provided an advantage over the chevron nozzle due to the decreasing self-noise production when the Mach number of the jet was lower than 0.9. Moreover, numerical predictions which are provided by the Large Eddy Simulation were used to estimate the noise mitigation by performing turbulence statistical analysis. Numerical results which refer to the turbulent statistics are discussed in order to define how they can be affected to the acoustic results at the side of the jet. This shows how each device can deform the shear layer without producing additional streamwise and small scale vortices.

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Experimental Analysis for Jet Noise Reduction of Chevron Pylon-Based Nozzles

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1078.183 ◽

2014 ◽

Vol 1078 ◽

pp. 183-186 ◽

Cited By ~ 1

Author(s):

Jing Yu He ◽

Ying Bo Xu

Keyword(s):

Noise Reduction ◽

Experimental Analysis ◽

High Frequency ◽

Sound Pressure ◽

Low Frequency ◽

Jet Noise ◽

Separate Flow ◽

Frequency Noise ◽

Chevron Nozzle ◽

Chevron Nozzles

The experimental analysis is conducted for jet noise reduction of separate flow chevron pylon-based nozzles at takeoff condition. The experimental results indicate that the pylon makes a noise reduction at low-frequency but produces an increase at high-frequency, together with an overall sound pressure reduction below the pylon. Compared to chevron nozzle without pylon, the adding of a pylon reduces noise benefit of chevron nozzles found in the isolated nozzle without a pylon. The best low-frequency noise reduction is located below the pylon where peak noise reduction is as high as about 1.3dB on frequency spectrum.

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A new method of fluxgate signal extraction

Information extraction and processing ◽

10.15407/vidbir2017.45.083 ◽

2017 ◽

Vol 2017 (45) ◽

pp. 83-89

Author(s):

A.A. Marusenkov ◽

Keyword(s):

High Frequency ◽

Second Harmonic ◽

Excitation Frequency ◽

Low Noise ◽

Measuring System ◽

Signal Extraction ◽

Fluxgate Magnetometer ◽

New Approach ◽

Average Value ◽

The Time Domain

Using dedicated high-frequency measuring system the distribution of the Barkhausen jumps intensity along a reversal magnetization cycle was investigated for low noise fluxgate sensors of various core shapes. It is shown that Barkhausen (reversal magnetization) noise intensity is strongly inhomogeneous during an excitation cycle. In the traditional second harmonic fluxgate magnetometers the signals are extracted in the frequency domain, as a result, some average value of reversal magnetization noises is contributed to the output signals. In order to fit better the noise shape and minimize its transfer to the magnetometer output the new approach for demodulating signals of these sensors is proposed. The new demodulating method is based on information extraction in the time domain taking into account the statistical properties of cyclic reversal magnetization noises. This approach yields considerable reduction of the fluxgate magnetometer noise in comparison with demodulation of the signal filtered at the second harmonic of the excitation frequency.

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Low Noise Measurements in an RF Environment

10.21236/ada273813 ◽

1993 ◽

Author(s):

Daniel E. Warren

Keyword(s):

Low Noise ◽

Noise Measurements

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Ultra low-noise preamplifier for low-frequency noise measurements in electron devices

IEEE Transactions on Instrumentation and Measurement ◽

10.1109/19.69939 ◽

1991 ◽

Vol 40 (1) ◽

pp. 2-6 ◽

Cited By ~ 55

Author(s):

B. Neri ◽

B. Pellegrini ◽

R. Saletti

Keyword(s):

Low Frequency ◽

Low Noise ◽

Frequency Noise ◽

Low Frequency Noise ◽

Noise Measurements ◽

Electron Devices ◽

Ultra Low Noise ◽

Low Noise Preamplifier

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Twin jet noise shielding for a supersonic cruise vehicle

10.2514/6.1979-670 ◽

1979 ◽

Author(s):

J. CLAUSS, JR. ◽

B. WRIGHT ◽

G. BOWIE

Keyword(s):

Jet Noise ◽

Noise Shielding

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New Method to Determine the a-Si:H Pin Diode Series Resistance by Noise Measurements

MRS Proceedings ◽

10.1557/proc-507-169 ◽

1998 ◽

Vol 507 ◽

Cited By ~ 2

Author(s):

F. Blecher ◽

K. Seibel ◽

M. Hillebrand ◽

M. Böhm

Keyword(s):

Series Resistance ◽

Partial Information ◽

Low Noise ◽

Operating Conditions ◽

New Method ◽

Measuring System ◽

Pin Diode ◽

Noise Current ◽

Current Voltage ◽

Noise Measurements

ABSTRACTThe series resistance limits the linearity of photodiodes and decreases the efficiency of solar cells. It is usually determined from IV-measurements for moderate and high forward current density. This method, however, provides only partial information about Rs, since the series resistance depends on the operating point. An alternative method is based on noise measurements. System noise of the measuring system with a low-noise current-voltage converter has been investigated. A new method for extraction of photodiode series resistance from noise measurements is suggested. Noise measurements are carried out for a-Si:H pin diodes. The series resistance of an amorphous pin diode has been extracted for different operating conditions using the new measurement method.

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