The Noise and Flow Characteristics of Inverted-profile Coannular Jets PDF Download
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Author:
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Category :
Languages : en
Pages : 442
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Author:
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ISBN:
Category :
Languages : en
Pages : 442
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Author: H. K. Tanna
Publisher:
ISBN:
Category :
Languages : en
Pages : 160
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Author: J. W. Russell
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Category : Acoustical engineering
Languages : en
Pages : 164
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A coannular jet was equated with a single stream equivalent jet with the same mass flow, energy, and thrust. The acoustic characteristics of the coannular jet were then related to the acoustic characteristics of the single jet. Forward flight effects were included by incorporating a forward exponent, a Doppler amplification factor, and a Strouhal frequency shift. Model test data, including 48 static cases and 22 wind tunnel cases, were used to evaluate the prediction method. For the static cases and the low forward velocity wind tunnel cases, the spectral mean square pressure correlation coefficients were generally greater than 90 percent, and the spectral sound pressure level standard deviation were generally less than 3 decibels. The correlation coefficient and the standard deviation were not affected by changes in equivalent jet velocity. Limitations of the prediction method are also presented.
Author: S. Paul Pao
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ISBN:
Category : Jet planes
Languages : en
Pages : 132
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Data are correlated for jet mixing noise from coannular jets with inverted flow velocity profiles. The acoustic performance of coannular jets is compared to the performance of a hypothetical single jet with the same total mass flow, thrust, and total enthalpy flow as the coannular jet. The study shows that coannular jets with velocity ratios greater than 1.2 produce less noise than their corresponding equivalent tests and that optimum noise reduction of coannular jets in the data set occurs within a range of equivalent velocities between 500 and 700 meters per second and velocity ratios between 1.6 and 2.3. The maximum sound power reduction is found to be about 4 decibels. Directivity indices and a special set of spectral curves were developed to describe the characteristic double peak spectra of coannular jet noise. The temperature ratio between the inner and outer streams was not found to be important in this acoustic correlation. However, the mean temperature effect was included in the computations of sound pressure levels.
Author: J. W. Russel
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 164
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Author: Hilary Kozlowski
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Category : Airplanes
Languages : en
Pages : 204
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Author:
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ISBN:
Category : Jet planes
Languages : en
Pages : 127
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The results of the investigation of the noise characteristics of the exhaust jets from coannular nozzles with conventional and inverted velocity profiles are presented. Experiments were carried out on a series of coannular nozzles of equal primary and secondary area. The majority of acoustic tests were carried out holding either the total thrust or the total mass flow constant while varying the rates of secondary velocity to primary velocity. A limited number of tests were also made simulating the takeoff, cutback and approach conditions of the JT8D engine and corresponding inverted conditions. The results of this study show that at high thrust level the coannular flows with inverted velocity profiles are quieter than those with standard velocity profiles at the same thrust and the same mass flow. The acoustic differences are much greater when the velocity ratio is produced by differences in the stagnation temperature rather than by differences in the stagnation pressure. (Author).
Author:
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Category : Aeronautics
Languages : en
Pages : 1370
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author:
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Category : Aeronautics
Languages : en
Pages : 104
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Author:
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ISBN:
Category : Science
Languages : en
Pages : 84
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