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Research Papers: Gas Turbines: Structures and Dynamics

Computational Fluid Dynamics Simulations of Flow and Heat Transfer in a Preswirl System: Influence of Rotating-Stationary Domain Interface

[+] Author and Article Information
Joachim Karnahl

Institute of Aerospace Thermodynamics,  Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germanyjoachim.karnahl@itlr.uni-stuttgart.de

Jens von Wolfersdorf

Institute of Aerospace Thermodynamics,  Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germanyjens.vonwolfersdorf@itlr.uni-stuttgart.de

Kok-Mun Tham

 Siemens Energy, Inc., 4400 Alafaya Trail, Orlando, FL 32826

Mike Wilson, Gary Lock

Department of Mechanical Engineering,  University of Bath, Bath, BA2 7AY, UK

J. Eng. Gas Turbines Power 134(5), 052502 (Feb 21, 2012) (11 pages) doi:10.1115/1.4004730 History: Received May 31, 2011; Revised June 28, 2011; Published February 21, 2012; Online February 21, 2012

This paper presents computational fluid dynamics (CFD) predictions of flow and heat transfer for an over-swirled low-radius preswirl system and comparison with experimental data. The rotor-stator CFD model comprises a stationary domain with the preswirl nozzles and a rotating domain with the receiver holes. The fluid-dynamic conditions feature an over-swirled system with a swirl ratio at the nozzle radius βp  = 1.4−1.5 and rotational Reynolds number ReΦ  = 0.8 × 106 and 1.2 × 106 . Three different treatments for the rotating and stationary domain interface are used to evaluate the influence on the flow and heat transfer behavior: a stationary approach (including Coriolis forces in the rotating domain) with “direct connection” and fixed angle between preswirl nozzle and receiver holes; a stationary approach with circumferential averaging of the velocity at radial bands; and a full transient simulation with the rotating domain capturing the unsteady flow due to the rotating receiver holes. Results at different circumferential angles show high variability in pressure and velocity distributions at the preswirl inlet nozzle radius. Circumferential averaging of these flow parameters lead to an alignment of the pressures and velocities between the three different interface approaches. Comparison with experimental pressure and swirl-ratio data show a quantitative agreement but the CFD results feature a systematic overestimation outward of the preswirl nozzle radius. Heat transfer coefficient distributions at the rotor surface show the effect of the different interface approaches and dependence on the flow structure (for example the impinging jet and vortex structures). The three different interface approaches result in significant differences in the computed heat transfer coefficients between pairs of receiver holes. Circumferentially averaged heat transfer coefficients inward of the receiver holes radius show good agreement between the transient and stationary direct connection interfaces, whereas those for the circumferential averaging interface differ, contrary to the flow parameters, due to smoothing of local effects from the preswirl jets.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic diagram of the rotor-stator test rig after Yan [18]

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Figure 2

Section of the stationary mesh part with preswirl nozzle

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Figure 3

15°/12° model domain

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Figure 4

Mesh sensitivity: differences in heat transfer coefficient along a radial line between receiver holes

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Figure 5

Velocity and stream lines for the 15°/12° model on a meridional plane at preswirl nozzle radius r/b = 0.74 (left side = stationary domain)

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Figure 6

Static pressure levels”15°/12° Trans.” (ReΦ  = 1.2 × 106 , radial lines at several positions θ)

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Figure 7

Detail view of preswirl nozzle exit

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Figure 8

Circumferentially averaged static pressures at stator (ReΦ  = 1.2 × 106 )

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Figure 9

Circumferentially averaged total pressures at midsurface (ReΦ  = 1.2 × 106 )

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Figure 10

Circumferentially averaged swirl ratio at midsurface (ReΦ  = 1.2 × 106 )

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Figure 11

Heat transfer coefficient distribution plots (rotor, ReΦ  = 1.2 × 106 )

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Figure 12

Vortical structures with Q = 4 e + 7 (1/s2 ) (ReΦ  = 1.2 × 106 , view through stator wall)

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Figure 13

Heat transfer coefficient distribution (ReΦ  = 1.2 × 106 )

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Figure 14

Circumferential evaluation of heat flux at the rotor for different interfaces at r/b = 0.74 and r/b = 0.76 (ReΦ  = 1.2 × 106 )

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Figure 15

Heat transfer coefficient distribution (ReΦ  = 0.8 × 106 )

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