Estimation of the far-field directivity of broadband aeroengine fan noise using an in-duct axial microphone array

2010 ◽  
Vol 329 (19) ◽  
pp. 3940-3957 ◽  
Author(s):  
C.R. Lowis ◽  
P.F. Joseph ◽  
A.J. Kempton
Keyword(s):  
Author(s):  
Jin-Hwa Kim ◽  
Martin Kearney-Fischer ◽  
Mo Samimy ◽  
Sivaram Gogineni

Plasma actuators are used to control far-field noise in Mach 1.65 jets from contoured and conical supersonic axisymmetric nozzles (henceforth, contoured and conical jets, respectively). The contoured nozzle is designed using the method of characteristics for a shock-free jet. The conical nozzle has converging and diverging conical sections with a sharp throat. Eight plasma actuators, distributed uniformly around the nozzle exit, are used and the jet is forced with azimuthal modes (m) 0–3 and ±4 and forcing Strouhal numbers ranging from 0.09 to 4.0. The far-field acoustic noise is measured by a linear microphone array covering polar angles from 25 deg to 80 deg relative to the jet axis. In both jets, the lower forcing azimuthal modes (m=0 and 1) are less effective than the higher modes (m=2, 3, and ±4), which have similar levels of overall sound pressure level (OASPL) reduction. At shallow angles relative to the jet axis, the reduction in OASPL is about 1.6–1.8 dB at low forcing Strouhal numbers in both jets at the most effective forcing mode of m=3. However, the OASPL in the sideline direction is only slightly increased (about 1 dB) for both the contoured and conical jets at m=3. The reduction at shallow polar angles is related to the decrease in the peak mixing noise level in both jets. The range of forcing Strouhal numbers providing significant noise reduction and the range of polar angles over which the noise is reduced are both much larger in the conical jet compared with the contoured jet. The screech tones are also reduced or suppressed – most likely due to weakening of naturally occurring structures by forcing.


1997 ◽  
Vol 102 (5) ◽  
pp. 3208-3208
Author(s):  
Darren B. Ward ◽  
Rodney A. Kennedy ◽  
Thushara Abhayapala

Author(s):  
Pengfei Chai ◽  
Zonghan Sun ◽  
Zhiqiang Chang ◽  
Zhigang Peng ◽  
Jie Tian ◽  
...  

Abstract The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.


2021 ◽  
Author(s):  
Pengfei Chai ◽  
Zonghan Sun ◽  
Zhiqiang Chang ◽  
Zhigang Peng ◽  
Jie Tian ◽  
...  

Abstract The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.


1984 ◽  
Author(s):  
P. SCHWALLER ◽  
A. PARRY ◽  
M. OLIVER ◽  
A. ECCLESTON

Author(s):  
Richard Woodward ◽  
Christopher Hughes ◽  
Robert Jeracki ◽  
Christopher Miller

Author(s):  
Danilo S. Braga ◽  
Andre Spillere ◽  
Julio A. Cordioli ◽  
Andrey R. da Silva ◽  
Danillo C. Reis

Author(s):  
Piergiorgio Ferrante ◽  
Paolo di Francescantonio ◽  
Pierre-Alain Hoffer ◽  
Stéphane Vilmin ◽  
Charles Hirsch

An innovative computational approach, integrating mesh generation, CFD simultaneous analysis of noise source and propagation, with acoustic radiation, is presented and applied to the simulation of the Advanced Noise Control Fan (ANCF) developed by NASA Glenn Research Center. The tonal noise source and the sound propagation in the nacelle duct and in the nacelle near field are simultaneously predicted, starting from the engine geometry and parameters, with a single CFD analysis based on an efficient Nonlinear Harmonic (NLH) method. The sound radiation to the far field is computed with the Green’s function approach implemented in a BEM frequency domain solver of the convective Helmholtz equation. The present method provides to a gain of close to two orders of magnitude compared to standard approaches, based on full unsteady flow simulations, followed by a near-field FEM based approach and a BEM method for the far-field noise propagation. The final comparison between the numerical results and the measurements highlights the capability of the methodology to efficiently predict the unsteady flow field and the radiated sound field.


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