Research Papers: Gas Turbines: Aircraft Engine

LES Predictions of Noise Emissions From a Low-Bypass Ratio Military Gas Turbine Engine

[+] Author and Article Information
N. Sinha, J. Erwin, C. Kannepalli

 Combustion Research and Flow Technology, Inc., (CRAFT Tech), Pipersville, PA 18947

J. Eng. Gas Turbines Power 133(4), 041202 (Nov 19, 2010) (10 pages) doi:10.1115/1.4002274 History: Received June 01, 2010; Revised June 10, 2010; Published November 19, 2010; Online November 19, 2010

A practical framework for predicting jet structure and noise from military aircraft is described, which is developmental and has been examined for some fundamental jet flow problems. The framework currently utilizes Reynolds-averaged Navier Stokes (RANS) methodology for geometrically complex internal propulsive flowpaths and large eddy simulation (LES) methodology for the jet structure downstream of the nozzle exit. Temporal data from the LES solution is stored on a flared-cylindrical surface surrounding the jet, to be used for noise propagation to the farfield. Earlier applications of RANS methodology combined with the use of analogy-based jet noise codes proved inadequate due to the inability of the noise codes to treat complex 3D flows, such as those associated with multiple nozzles and/or with varied jet noise reduction concepts. Restricting the use of LES (or RANS/LES), methodology to free shear flows remedies the severe grid resolution issues that would be encountered with utilization of LES for modeling internal propulsive flows. The issue of “adequately” initiating the LES solution from a RANS solution profile just downstream of the nozzle exit has been the focus of our exploratory studies and is clearly more complex than standard procedures, such as recycling and rescaling techniques used for simple wall bounded flows. Approaches examined are discussed and unified RANS/LES solutions for several flows are described. The application of this framework to more complex flows requires no fundamental modifications as will also be discussed.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Schematic of end-to-end model for supersonic jet noise emission predictions

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Figure 2

Variation of the energy containing wave number with the Taylor scale Reynolds number

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Figure 3

Ratio of subgrid eddy viscosity to the RANS eddy viscosity as a function of the resolution

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Figure 4

ADS placement in linear wave propagation region

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Figure 5

O-H grid used for large eddy simulation of jets

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Figure 6

Static temperature contours for engine with near-wall cold bypass stream (boundary layer)

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Figure 7

Mach number contours for engine with over-expanded nozzle and Mach disk

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Figure 8

Plume Mach number contours

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Figure 9

Plume TKE contours

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Figure 10

Instantaneous contours of (a) Mach number and (b) temperature in XY plane

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Figure 11

Mean (Favré-averaged): (a) U-velocity, (b) temperature, and (c) TKE in XY plane

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Figure 12

Comparisons of centerline distribution of (a) U-velocity and (b) TKE

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Figure 13

Time average Mach and instantaneous temperature

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Figure 14

OASPL directivity for pressure balanced cold jet

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Figure 15

1/3 octave SPL for Tanna jet at 30 deg angle

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Figure 16

Time-averaged mach and instantaneous temperature

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Figure 17

Shock cells in under-expanded cold jet

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Figure 18

Instantaneous Mach contours illustrating development of the laboratory jet

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Figure 19

Instantaneous temperature contours in XY plane

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Figure 20

Time-averaged mach number contours

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Figure 21

OASPL directivity for hot laboratory jet

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Figure 22

1/3 octave spectra at 50 deg and 120 deg observer

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Figure 23

Instantaneous temperature contours

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Figure 24

Time-averaged Mach number contours

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Figure 25

OASPL and spectra comparisons for engine test




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