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Research Papers

Compressor Performance and Operability in Swirl Distortion

[+] Author and Article Information
Yogi Sheoran

 Honeywell Aerospace, 111 South 34th Street M/S 503-428, Phoenix, AZ 85034yogi.sheoran@honeywell.com

Bruce Bouldin

 Honeywell Aerospace, 111 South 34th Street M/S 503-428, Phoenix, AZ 85034bruce.bouldin@honeywell.com

P. Murali Krishnan

 Honeywell Technology Solutions, Survey No. 19/2, Devarabisanahalli Village, KR Puram Hobli, Bangalore East Taluk, Bangalore 560 037, Indiamurali.p@honeywell.com

J. Turbomach 134(4), 041008 (Jul 20, 2011) (13 pages) doi:10.1115/1.4003657 History: Received September 10, 2010; Revised October 25, 2010; Published July 20, 2011; Online July 20, 2011

Inlet swirl distortion has become a major area of concern in the gas turbine engine community. Gas turbine engines are increasingly installed with more complicated and tortuous inlet systems such as those found on embedded installations on unmanned aerial vehicles. These inlet systems can produce complex swirl patterns in addition to total pressure distortion. The effect of swirl distortion on engine or compressor performance and operability must be evaluated. The gas turbine community is developing methodologies to measure and characterize swirl distortion. There is a strong need to develop a database containing the impact of a range of swirl distortion patterns on a compressor performance and operability. A recent paper presented by the authors described a versatile swirl distortion generator system that produced a wide range of swirl distortion patterns of a prescribed strength, including bulk swirl, twin swirl, and offset swirl. The design of these swirl generators greatly improved the understanding of the formation of swirl. The next step of this process is to understand the effect of swirl on compressor performance. A previously published paper by the authors used parallel compressor analysis to map out different speed lines that resulted from different types of swirl distortion. For the study described in this paper, a computational fluid dynamics (CFD) model is used to couple upstream swirl generator geometry to a single stage of an axial compressor in order to generate a family of compressor speed lines. The complex geometry of the analyzed swirl generators requires that the full 360 deg compressor be included in the CFD model. A full compressor can be modeled several ways in a CFD analysis, including sliding mesh and frozen rotor techniques. For a single operating condition, a study was conducted using both of these techniques to determine the best method, given the large size of the CFD model and the number of data points that needed to be run to generate speed lines. This study compared the CFD results for the undistorted compressor at 100% speed to comparable test data. Results of this study indicated that the frozen rotor approach provided just as accurate results as the sliding mesh but with a greatly reduced cycle time. Once the CFD approach was calibrated, the same techniques were used to determine compressor performance and operability when a full range of swirl distortion patterns were generated by upstream swirl generators. The compressor speed line shift due to co-rotating and counter-rotating bulk swirl resulted in a predictable performance and operability shift. Of particular importance is the compressor performance and operability resulting from an exposure to a set of paired swirl distortions. The CFD generated speed lines follow similar trends to those produced by parallel compressor analysis.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Typical APU inlet systems include many changes in direction and shape

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Figure 2

Typical bulk swirl pattern

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Figure 3

Two types of paired swirl patterns

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Figure 4

Typical 1/rev paired swirl pattern at constant radius

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Figure 6

Spectrum of SP with 1/rev maximum

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Figure 7

Cut-away of ASE120 engine with LPC visible

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Figure 8

Baseline CFD model with no swirl generation

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Figure 9

CFD model with swirl generator attached to compressor first stage

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Figure 10

Semispherical farfield used on CFD model

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Figure 11

Comparison of CFD techniques for rotating geometry

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Figure 12

Generic swirl generator configuration

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Figure 13

Twin swirl generator

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Figure 14

Twin swirl pattern represented by velocity vectors

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Figure 15

Positive bulk swirl generator

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Figure 16

Positive bulk swirl pattern

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Figure 17

Negative bulk swirl generator

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Figure 18

Negative bulk swirl pattern

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Figure 19

Positive offset swirl generator

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Figure 20

Generated positive offset swirl pattern

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Figure 21

Negative offset swirl generator

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Figure 22

Negative offset swirl pattern

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Figure 23

Indications of stall in the CFD model

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Figure 24

Effect of bulk swirl on compressor map

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Figure 25

Negative swirl results in lower efficiency

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Figure 26

Smaller speed line shift with total temperature ratio

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Figure 27

Effect of twin swirl on compressor map

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Figure 28

Effect of offset swirl on compressor map

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Figure 29

Effect of swirl on compressor efficiency

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Figure 30

Effect of swirl on total temperature ratio

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