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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

A Comprehensive Investigation of Preswirled Flow Through Rotating Radial Holes

[+] Author and Article Information
Daniel Riedmüller

Institut für Thermodynamik LRT-10,
Fakultät für Luft- und Raumfahrttechnik,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: daniel.riedmueller@unibw.de

Jan Sousek

Institut für Thermodynamik LRT-10,
Fakultät für Luft- und Raumfahrttechnik,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: sousek.jan@seznam.cz

Michael Pfitzner

Institut für Thermodynamik LRT-10,
Fakultät für Luft- und Raumfahrttechnik,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: michael.pfitzner@unibw.de

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 11, 2014; final manuscript received July 18, 2014; published online October 7, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(3), 031504 (Oct 07, 2014) (13 pages) Paper No: GTP-14-1376; doi: 10.1115/1.4028375 History: Received July 11, 2014; Revised July 18, 2014

This paper reports on the flow (centrifugal = radially outward, centripetal = radially inward) through rotating radial orifices with and without preswirl in the flow approaching the orifice in the outer annulus. The aerodynamical behavior of flow through radial rotating holes is different from the one through axial and stationary holes due to the presence of centrifugal and Coriolis forces. To investigate the flow phenomena and the discharge coefficient of these orifices in detail, an existing test rig containing two independently rotating shafts (corotating and counter rotating) was used. To simulate conditions of real gas turbines, where the flow is often influenced by upstream components, various preswirl angles were used in the test rig. Measurements of the flow discharge coefficient in both flow directions through the orifices (centripetal and centrifugal), with and without preswirl generation in the outer annulus, are presented at various flow conditions (pressure ratios across orifices, Mach numbers of approaching flow) and for different geometric parameters (length to diameter ratios, sharp/rounded inlet edges). Flow effects that occur with preswirled flow are clarified. A comparison of the experimental data, for both flow directions, shows a similar behavior of the discharge coefficients with increasing shaft speeds. To supplement the experimental data and to better understand the experimental findings, numerical simulations were performed, which show a good agreement with the experimental results. Furthermore, an optimization model with complete automatic grid generation, computational fluid dynamics (CFD) simulation, and postprocessing, was built to enable large parametric studies, e.g., grid independence of the solutions.

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References

Figures

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Fig. 1

Schematic line drawing of air supply

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Fig. 4

Inflow structure of the inner channel

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Fig. 5

Velocity triangles at the orifice: (a) flow without crossflow, (b) flow with crossflow, and (c) flow with crossflow and swirl

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Fig. 6

Computational domain

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Fig. 7

Velocity angle at the profile stage for the swirl generator 25 deg (cf. Sousek et al. [11])

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Fig. 8

Boundary conditions for the inner intake

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Fig. 9

Mach number contour plot of the inner intake

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Fig. 10

Boundary conditions for the annular section

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Fig. 11

Schematic for parametric studies

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Fig. 12

Grids with sharp (a) and rounded (b) inlet edge for centrifugal flow simulations

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Fig. 13

Effect of corotating or counter-rotating outer shaft on preswirled incident flow

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Fig. 14

Inflexion loops for L/D = 1.2 (swirl = 25 deg)

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Fig. 15

Inflexion loops for L/D = 0.6 (swirl = 25 deg)

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Fig. 16

Inflexion loops reproduced by the CFD

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Fig. 17

Flow vectors in the orifice for swirl generator with 25 deg (L/d = 1.2; r/d = 0 (sharp inlet); Π = 1.25; Max = 0.1) (cf. Sousek et al. [11])

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Fig. 18

Effects of the fictitious forces (U = 8000 l/min; L/d = 1.2; r/d = 0 (sharp inlet)

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Fig. 19

Effects of fictitious forces on the discharge

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Fig. 20

Inflow profile with SBV

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Fig. 21

Circumferential velocity profiles with preswirl and SBV (relative frame of reference)

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Fig. 22

Discharge coefficient for swirl = 45 deg (L/d = 1.2; r/d = 0 (sharp inlet); Max = 0.1–0.2)

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Fig. 23

Discharge coefficient for swirl = 45 deg (L/d = 0.6; r/d = 0 (sharp inlet); Max = 0.1–0.2)

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Fig. 24

Comparison of the flow directions with error bars (L/d = 1.2; r/d = 0 (sharp inlet); Max = 0.1)

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Fig. 25

Comparison of the flow directions (L/d = 0.6; r/d = 0 (sharp inlet); Max = 0.1)

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Fig. 26

Comparison of the flow directions (L/d = 1.2; r/d = 0.2 (rounded inlet); Max = 0.1)

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Fig. 27

Comparison of the flow directions (L/d = 0.6; r/d = 0.2 (rounded inlet); Max = 0.1)

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Fig. 28

Comparison of CFD and experiment for the centrifugal flow direction (L/d = 1.2; r/d = 0 (sharp inlet); Max = 0.1)

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Fig. 29

Comparison of CFD and experiment for the centrifugal flow direction (L/d = 1.2; r/d = 0.2 (rounded inlet); Max = 0.1)

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Fig. 30

Comparison of CFD and experiment for the centrifugal flow direction (L/d = 0.6; r/d = 0 (sharp inlet); Max = 0.1)

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Fig. 31

Comparison of CFD and experiment for the centrifugal flow direction (L/d = 0.6; r/d = 0.2 (rounded inlet); Max = 0.1)

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Fig. 32

Flow vectors in the orifice for centrifugal flow and rounded inlet (L/d = 0.6; r/d = 0.2; Π = 1.5; Max = 0.1)

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Fig. 33

Comparison of CFD results for the centrifugal flow with changing radius of the inner shaft (L/d = 0.6; r/d = 0.2 (rounded inlet); Max = 0.1)

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Fig. 34

Comparison of CFD results for centrifugal and centripetal flow with equal gap distances of the inner and outer annulus (L/d = 0.6; r/d = 0.2 (rounded inlet); Max = 0.1)

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