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Gas Turbines: Aircraft Engine

Effects of Core Flow Swirl on the Flow Characteristics of a Scalloped Forced Mixer

[+] Author and Article Information
Zhijun Lei

 Gas Turbine Laboratory, Institute for Aerospace Research, National Research Council of Canada, Ottawa, ON, Canada

Ali Mahallati1

 Gas Turbine Laboratory, Institute for Aerospace Research, National Research Council of Canada, Ottawa, ON, Canadaali.mahallati@nrc-cnrc.gc.ca

Mark Cunningham, Patrick Germain

 Installation and Turbine Aerodynamics, Pratt & Whitney Canada, Longueuil, PQ, Canada

1

Corresponding author:

J. Eng. Gas Turbines Power 134(11), 111201 (Sep 21, 2012) (9 pages) doi:10.1115/1.4005968 History: Received July 02, 2011; Revised August 02, 2011; Published September 20, 2012; Online September 21, 2012

This paper presents a detailed experimental investigation of the influence of core flow swirl on the mixing and performance of a scaled turbofan mixer with 12 scalloped lobes. Measurements were made downstream of the mixer in a coaxial wind tunnel. The core-to-bypass velocity ratio was set to 2:1, temperature ratio to 1.0, and pressure ratio to 1.03, giving a Reynolds number of 5.2 × 105 , based on the core flow velocity and equivalent diameter. In the core flow, the background turbulence intensity was raised to 5% and the swirl angle was varied from 0 deg to 30 deg with five vane geometries. At low swirl angles, additional streamwise vortices were generated by the deformation of normal vortices due to the scalloped lobes. With increased core swirl, greater than 10 deg, the additional streamwise vortices were generated mainly due to radial velocity deflection, rather than stretching and deformation of normal vortices. At high swirl angles, stronger streamwise vortices and rapid interaction between various vortices promoted downstream mixing. Mixing was enhanced with minimal pressure and thrust losses for the inlet swirl angles less than 10 deg. However, the reversed flow downstream of the center body was a dominant contributor to the loss of thrust at the maximum core flow swirl angle of 30 deg.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Cutaway of the test section

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Figure 2

Scalloped lobed mixer geometry

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Figure 3

Surface oil-flow visualization for the baseline case

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Figure 4

Velocity fields for the baseline case

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Figure 5

Streamwise and azimuthal vorticity fields for the baseline case

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Figure 6

Mixing indices for the baseline and 0 deg swirl cases

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Figure 7

Surface oil-flow visualization for high angle swirls

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Figure 8

Velocity fields for the 10 deg and 30 deg inlet swirls—axial planes

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Figure 9

Total pressure and velocity fields for the 10 deg and 30 deg inlet swirls—meridional planes

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Figure 10

Streamwise and azimuthal vorticity fields for 10 deg inlet swirl

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Figure 11

Streamwise and azimuthal vorticity fields for 30 deg inlet swirl

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Figure 12

Streamwise circulation at the x/Dh  = 0.07 plane

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Figure 13

Streamwise circulation downstream of the mixer

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Figure 14

Total and static pressure mixing indices

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Figure 15

Total pressure loss coefficients

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Figure 16

Thrust coefficient

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