Fan Noise Source Diagnostic Test - Tone Modal Structure Results

Heidelberg, Laurence J.

doi:10.2514/6.2002-2428

Cited by 48 publications

(32 citation statements)

References 3 publications

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“…Some works have highlighted the effects of the geometrical parameters such as the vane sweep or blade and vane counts for rotor/stator interaction noise. The most detailed investigation is the "Fan Noise Source Diagnostic Test" reported by NASA [2][3][4][5]. It deals with a stator with 54 radial vanes, a low-count stator with 26 radial vanes, and a low-noise stator with 26 swept vanes.…”

mentioning

confidence: 99%

Experimental Validation of a Cascade Response Function for Fan Broadband Noise Predictions

Posson

Roger

2011

AIAA Journal

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The present paper is aimed at assessing an analytical prediction model for the broadband noise produced by the impingement of turbulence on a cascade, using a dedicated experiment. The model is a strip-theory approach based on a previously published formulation of the unsteady blade loading for a rectilinear cascade. The experimental setup is made of a single stationary cascade of vanes mounted downstream of a turbulence grid in an annular duct, at the exit of an open-jet anechoic wind tunnel. The statistical parameters of the turbulence measured with hot-wire anemometry are used as input data in the model. The in-duct predicted downstream acoustic power is compared with the measured power obtained from the far-field acoustic pressure. Measured and predicted variations of the acoustic power with the number of vanes of the cascade and with the turbulence intensity are found to be in good agreement. It is concluded that the analytical approach succeeds in highlighting three-dimensional effects and is promising for further comparisons in more complex annular configurations. = squared norm of the duct eigenfunction E m; = microphone angle in the horizontal plane P containing the center of the exhaust section = turbulence integral length scale 0 = exponential correction factor of the turbulence spectrum 0 = fluid density = interblade phase angle uu ! = power spectral density of the streamwise velocity ww K; r = three-dimensional wave-number turbulence spectrum for the vane normal velocity component divided by u 2 rmŝ ' = sweep angle in the duct reference framê = stagger angle in the duct reference frame m;= eigenvalue of the mode m;

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mentioning

confidence: 99%

Experimental Validation of a Cascade Response Function for Fan Broadband Noise Predictions

Posson

Roger

2011

AIAA Journal

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“…(7) is the root of Eq. (8). It is well known that for a fixed radial mode number n, the value of  mn from Eq.…”

Section: Cantrell and Hartmentioning

confidence: 99%

“…Acoustic radiation from jet engine inlets has been studied experimentally [1][2][3][4][5][6][7][8][9] , analytically [10][11][12][13] and computationally [14][15][16][17][18][19][20][21][22][23][24][25][26] by a number of investigators in the past. These studies provide a variety of useful and interesting information.…”

Section: Introductionmentioning

confidence: 99%

Physics of Acoustic Radiation from Jet Engine Inlets

Tam

Parrish

Envia

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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Numerical simulations of acoustic radiation from a jet engine inlet are performed using advanced computational aeroacoustics (CAA) algorithms and high-quality numerical boundary treatments. As a model of modern commercial jet engine inlets, the inlet geometry of the NASA Source Diagnostic Test (SDT) is used. Fan noise consists of tones and broadband sound. This investigation considers the radiation of tones associated with upstream propagating duct modes. The primary objective is to identify the dominant physical processes that determine the directivity of the radiated sound. Two such processes have been identified. They are acoustic diffraction and refraction. Diffraction is the natural tendency for an acoustic wave to follow a curved solid surface as it propagates. Refraction is the turning of the direction of propagation of sound waves by mean flow gradients. Parametric studies on the changes in the directivity of radiated sound due to variations in forward flight Mach number and duct mode frequency, azimuthal mode number, and radial mode number are carried out. It is found there is a significant difference in directivity for the radiation of the same duct mode from an engine inlet when operating in static condition and in forward flight. It will be shown that the large change in directivity is the result of the combined effects of diffraction and refraction.

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“…For this study, the 22-inch diameter NASA/GE Source Diagnostic Test (SDT) fan 5,6,7 is chosen. The SDT fan, shown in Figure 1, has a design corrected tip speed of 1,215 ft/sec, a stage pressure ratio of 1.47, and a bypass ratio of 8.9.…”

Section: Test Configurationmentioning

confidence: 99%

“…The fan stage has 22 blades and 54 stator vanes in its baseline configuration. This configuration was chosen because of its use in previous studies 8,9,10 and the availability of measured acoustic data 6,7 for further model validation. The cross-section of the SDT test configuration is shown in Figure 2 with candidate inlet and aft acoustic liner locations shaded in green.…”

Section: Test Configurationmentioning

confidence: 99%

Broadband Liner Optimization for the Source Diagnostic Test Fan

Nark

Jones

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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The broadband component of fan noise has grown in relevance with the utilization of increased bypass ratio and advanced fan designs. Thus, while the attenuation of fan tones remains paramount, the ability to simultaneously reduce broadband fan noise levels has become more appealing. This paper describes a broadband acoustic liner optimization study for the scale model Source Diagnostic Test fan. Specifically, in-duct attenuation predictions with a statistical fan source model are used to obtain optimum impedance spectra over a number of flow conditions for three liner locations in the bypass duct. The predicted optimum impedance information is then used with acoustic liner modeling tools to design liners aimed at producing impedance spectra that most closely match the predicted optimum values. Design selection is based on an acceptance criterion that provides the ability to apply increased weighting to specific frequencies and/or operating conditions. Typical tonal liner designs targeting single frequencies at one operating condition are first produced to provide baseline performance information. These are followed by multiple broadband design approaches culminating in a broadband liner targeting the full range of frequencies and operating conditions. The broadband liner is found to satisfy the optimum impedance objectives much better than the tonal liner designs. In addition, the broadband liner is found to provide better attenuation than the tonal designs over the full range of frequencies and operating conditions considered. Thus, the current study successfully establishes a process for the initial design and evaluation of novel broadband liner concepts for complex engine configurations.

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Fan Noise Source Diagnostic Test - Tone Modal Structure Results

Cited by 48 publications

References 3 publications

Experimental Validation of a Cascade Response Function for Fan Broadband Noise Predictions

Experimental Validation of a Cascade Response Function for Fan Broadband Noise Predictions

Physics of Acoustic Radiation from Jet Engine Inlets

Broadband Liner Optimization for the Source Diagnostic Test Fan

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