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Research Papers: Flows in Complex Systems

RANS Analyses of Turbofan Nozzles With Internal Wedge Deflectors for Noise Reduction

[+] Author and Article Information
James R. DeBonis1

Inlet and Nozzle Branch, NASA Glenn Research Center, Cleveland, OH 44135james.r.debonis@nasa.gov

1

Corresponding author.

J. Fluids Eng 131(4), 041104 (Mar 09, 2009) (17 pages) doi:10.1115/1.3089536 History: Received March 21, 2008; Revised January 22, 2009; Published March 09, 2009

Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of a promising concept for reducing the noise at take-off of dual-stream turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) a portion of the fan flow below the core flow, thickening and lengthening this layer between the high-velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds averaged Navier–Stokes (RANS) code, was used to analyze the flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Turbofan nozzle with wedge installed in the fan stream

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Figure 2

Schematic drawings of NASA GRC turbofan nozzles

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Figure 3

Grid of the 5BB nozzle with wedge installed in the fan stream

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Figure 4

Grid blocking structure

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Figure 5

Streamwise (xy-plane) contours of u-velocity, u/Uc, for 3BB nozzles

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Figure 6

Streamwise (xy-plane) contours of u-velocity, u/Uc, for 4BB nozzles

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Figure 7

Streamwise (xy-plane) contours of u-velocity, u/Uc, for 5BB nozzles

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Figure 8

Streamwise (xy-plane) contours of turbulent kinetic energy, k/Uc2, for 3BB nozzles

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Figure 9

Streamwise (xy-plane) contours of turbulent kinetic energy, k/Uc2, for 4BB nozzles

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Figure 10

Streamwise (xy-plane) contours of turbulent kinetic energy, k/Uc2, for 5BB nozzles

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Figure 11

Cross-plane (yz-plane) contours of u-velocity, u/Uc, for 3BB nozzles

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Figure 12

Cross-plane (yz-plane) contours of u-velocity, u/Uc, for 4BB nozzles

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Figure 13

Cross-plane (yz-plane) contours of u-velocity, u/Uc, for 5BB nozzles

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Figure 14

Cross-plane (yz-plane) contours of turbulent kinetic energy, k/Uc2, for 3BB nozzles

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Figure 15

Cross-plane (yz-plane) contours of turbulent kinetic energy, k/Uc2, for 4BB nozzles

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Figure 16

Cross-plane (yz-plane) contours of turbulent kinetic energy, k/Uc2, for 5BB nozzles

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Figure 17

Ratio of wedge nozzle to baseline nozzle performance

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Figure 18

Nozzle performance expressed as a thrust coefficient

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Figure 19

Force breakout for 5BB baseline and wedge nozzles

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Figure 20

Streamlines for the 5BB nozzle

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Figure 21

Component of the vertical thrust

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Figure 22

Comparison to experiment; u-velocity, u/Uc, for the 3BB nozzle with wedge, hot conditions

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Figure 23

Comparison to experiment; turbulent kinetic energy, k/Uc2, for the 3BB nozzle with wedge, hot conditions

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Figure 24

Comparison to experiment; u-velocity, u/Uc, for the 5BB nozzle with wedge, hot conditions

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Figure 25

Comparison to experiment; turbulent kinetic energy, k/Uc2, for the 5BB nozzle with wedge, hot conditions

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Figure 26

Comparison to experiment; u-velocity, u/Uc, for the 5BB nozzle with wedge, cold conditions

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Figure 27

Comparison to experiment; turbulent kinetic energy, k/Uc2, for the 5BB nozzle with wedge, cold conditions

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