Skewed blades in low pressure fans - A survey of noise reduction mechanisms

1997 ◽  
Author(s):  
Th. Carolus ◽  
M. Beiler ◽  
Th. Carolus ◽  
M. Beiler
Keyword(s):  
Noise Reduction ◽  
Low Pressure ◽  
Reduction Mechanisms

Numerical study on the airfoil self-noise of three owl-based wings with the trailing-edge serrations

2021 ◽  
pp. 095441002098822
Author(s):  
Dian Li ◽  
Xiaomin Liu ◽  
Lei Wang ◽  
Fujia Hu ◽  
Guang Xi
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Numerical Study ◽  
Barn Owl ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Trailing Edge ◽  
Reduction Mechanisms ◽  
Trailing Edge Serrations ◽  
Bionic Airfoil

Previous publications have summarized that three special morphological structures of owl wing could reduce aerodynamic noise under low Reynolds number flows effectively. However, the coupling noise-reduction mechanism of bionic airfoil with trailing-edge serrations is poorly understood. Furthermore, while the bionic airfoil extracted from natural owl wing shows remarkable noise-reduction characteristics, the shape of the owl-based airfoils reconstructed by different researchers has some differences, which leads to diversity in the potential noise-reduction mechanisms. In this article, three kinds of owl-based airfoils with trailing-edge serrations are investigated to reveal the potential noise-reduction mechanisms, and a clean airfoil based on barn owl is utilized as a reference to make a comparison. The instantaneous flow field and sound field around the three-dimensional serrated airfoils are simulated by using incompressible large eddy simulation coupled with the FW-H equation. The results of unsteady flow field show that the flow field of Owl B exhibits stronger and wider-scale turbulent velocity fluctuation than that of other airfoils, which may be the potential reason for the greater noise generation of Owl B. The scale and magnitude of alternating mean convective velocity distribution dominates the noise-reduction effect of trailing-edge serrations. The noise-reduction characteristic of Owl C outperforms that of Barn owl, which suggests that the trailing-edge serrations can suppress vortex shedding noise of flow field effectively. The trailing-edge serrations mainly suppress the low-frequency noise of the airfoil. The trailing-edge serration can suppress turbulent noise by weakening pressure fluctuation.

816 Noise reduction for a regenerative and vacuum boiler : The effect of subcooling on bubbles generated by the low-pressure boiling

2001 ◽  
Vol 2001.76 (0) ◽  
pp. _8-31_-_8-32_
Author(s):  
Atsushi HANADA ◽  
Kenji HATTORI ◽  
Hironobu UCHIYAMA ◽  
Junichi KURATA
Keyword(s):  
Noise Reduction ◽  
Low Pressure

scholarly journals A study of noise reduction mechanisms of jets with fluid inserts

2020 ◽  
Vol 476 ◽  
pp. 115331 ◽  
Author(s):  
Chitrarth Prasad ◽  
Philip J. Morris
Keyword(s):  
Noise Reduction ◽  
Reduction Mechanisms

Noise reduction mechanisms in supersonic jets with porous centerbodies

AIAA Journal ◽  
1985 ◽  
Vol 23 (5) ◽  
pp. 678-684 ◽  
Author(s):  
V. Kibens ◽  
R. W. Wlezien
Keyword(s):  
Noise Reduction ◽  
Supersonic Jets ◽  
Reduction Mechanisms

Preliminary Fan Design for a Silent Aircraft

2006 ◽  
Author(s):  
Daniel Crichton ◽  
Liping Xu ◽  
Cesare A. Hall
Keyword(s):  
Mach Number ◽  
Noise Reduction ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Shock Structure ◽  
Operating Point ◽  
Blade Passage ◽  
Fuel Burn ◽  
Primary Shock

Preliminary fan design for a functionally silent aircraft has been performed with noise reduction as the primary goal. For such an aircraft the fan design must, in addition to delivering low cruise fuel burn, enable low jet and fan source noise during take-off. This requires the fan to be operating at low pressure ratio and high efficiency during take-off and, for conditions where the relative tip Mach number onto the fan is supersonic, ensuring the primary shock structure is ingested into the blade passage. To meet these requirements, flyover and cruise flow coefficients are matched using a variable area nozzle at the same time as delivering low take-off FPR. This places the sideline operating point near the shoulder of the characteristic and fixes the top of climb and cruise fan pressure ratios. For a 4-engine, 250pax, 4000nm silent aircraft this approach leads to a top of climb FPR of 1.45 requiring a 39% increase in nozzle area at take-off. A fan rotor has been designed for this cycle with 20 blades, low tip loading and a 350m/s top of climb tip speed.

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