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Research Papers

Rounded Fin Edge and Step Position Effects on Discharge Coefficient in Rotating Labyrinth Seals

[+] Author and Article Information
Andrea Rapisarda

Dipartimento Energia,
Politecnico di Torino,
Turin 10129, Italy
e-mail: andrea.rapisarda@polito.it

Alessio Desando

Dipartimento Energia,
Politecnico di Torino,
Turin 10129, Italy
e-mail: alessio.desando@polito.it

Elena Campagnoli

Dipartimento Energia,
Politecnico di Torino,
Turin 10129, Italy
e-mail: elena.campagnoli@polito.it

Roberto Taurino

Dipartimento Energia,
Politecnico di Torino,
Turin 10129, Italy
e-mail: roberto.taurino@polito.it

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received March 27, 2015; final manuscript received September 11, 2015; published online October 21, 2015. Assoc. Editor: Kenichiro Takeishi.

J. Turbomach 138(1), 011005 (Oct 21, 2015) (17 pages) Paper No: TURBO-15-1058; doi: 10.1115/1.4031748 History: Received March 27, 2015; Revised September 11, 2015

The design of modern aircrafts propulsion systems is strongly influenced by the important objective of environmental impact reduction. Through a great number of researches carried out in the last decades, significant improvements have been obtained in terms of lower fuel consumption and pollutant emission. Experimental tests are a necessary step to achieve new solutions that are more efficient than the current designs, even if during the preliminary design phase, a valid alternative to expensive experimental tests is the implementation of numerical models. The processing power of modern computers allows indeed the simulation of more complex and detailed phenomena than the past years. The present work focuses on the implementation of a numerical model for rotating stepped labyrinth seals installed in low-pressure turbines. These components are widely employed in sealing turbomachinery to reduce the leakage flow between rotating components. The numerical simulations were performed by using computational fluid dynamics (CFD) methodology, focusing on the leakage performances at different rotating speeds and inlet preswirl ratios. Investigations on velocity profiles into seal cavities were also carried out. To begin with, a smooth labyrinth seal model was validated by using the experimental data found in the literature. The numerical simulations were extended to the honeycomb labyrinth seals, with the validation performed on the velocity profiles. Then, the effects of two geometrical parameters, the rounded fin tip leading edge, and the step position were numerically investigated for both smooth and honeycomb labyrinth seals. The obtained results are generally in good agreement with the experimental data. The main effect found when the fin tip leading edge was rounded was a large increase in leakage flow, while the step position contribution to the flow path behavior is nonmonotone.

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References

Figures

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Fig. 1

Forward- and backward-stepped labyrinth seal

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Fig. 5

Honeycomb cells grid

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Fig. 9

Convergent honeycomb labyrinth seal, π=1.05; k=0 (left) and k=0.3 (right)

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Fig. 10

Axial (left) and circumferential (right) velocity profiles at x2 for honeycomb convergent labyrinth seal, k=0.3

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Fig. 11

Divergent smooth labyrinth seal, π=1.05; k=0 (left) and k=0.3 (right)

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Fig. 12

Axial (left) and circumferential (right) velocity profiles at  x3 for smooth divergent labyrinth seal, k=0.3

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Fig. 13

Divergent honeycomb labyrinth seal,  π=1.05; k=0 (left) and k=0.3 (right)

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Fig. 14

Axial (left) and circumferential (right) velocity profiles at x3 for honeycomb divergent labyrinth seal, k=0.3

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Fig. 15

Square (left) and rounded (right) fin tip leading edge

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Fig. 3

Clearance grid thickenings adopted: MESH 1 (left), MESH 2 (center), and MESH 3 (right)

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Fig. 4

MESH 3, convergent flow

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Fig. 6

Convergent smooth labyrinth seal, π = 1.05; k = 0 (left) and k = 0.3 (right)

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Fig. 7

Axial (left) and circumferential (right) velocity profiles at x1 for smooth convergent labyrinth seal, k=0

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Fig. 8

Axial (left) and circumferential (right) velocity profiles at x2 for smooth convergent labyrinth seal, k=0.3

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Fig. 22

Rounded fin tip leading edge: axial (left) and circumferential (right) velocity profiles at  x3 for smooth divergent labyrinth seal

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Fig. 2

Boundary conditions

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Fig. 16

Rounded fin tip leading edge: nonrotating discharge coefficient for convergent flow labyrinth seals

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Fig. 17

Rounded fin tip leading edge: vena contracta effect on second fin tip for smooth (up) and honeycomb (down) labyrinth seals, convergent flow, nonrotating conditions

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Fig. 26

Step position: velocity contour for convergent smooth labyrinth seals

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Fig. 18

Rounded fin tip leading edge: axial (left) and circumferential (right) velocity profiles at  x2 for smooth convergent labyrinth seal

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Fig. 19

Rounded fin tip leading edge: axial (left) and circumferential (right) velocity profiles at  x2 for honeycomb convergent labyrinth seal

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Fig. 30

Step position: nonrotating discharge coefficient for divergent flow labyrinth seals

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Fig. 31

Step position: velocity contour for divergent smooth labyrinth seals

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Fig. 32

Step position: velocity contour for divergent honeycomb labyrinth seals

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Fig. 20

Rounded fin tip leading edge: nonrotating discharge coefficient for divergent flow labyrinth seals

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Fig. 23

Rounded fin tip leading edge: axial (left) and circumferential (right) velocity profiles at  x3 for honeycomb divergent labyrinth seal

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Fig. 24

Step position: nonrotating discharge coefficient for convergent flow labyrinth seals

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Fig. 25

Step position: eddy viscosity on nonrotating convergent smooth labyrinth seals

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Fig. 27

Step position: velocity contour for convergent honeycomb labyrinth seals

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Fig. 28

Step position: axial (left) and circumferential (right) velocity profiles at  x2 for smooth convergent labyrinth seal

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Fig. 29

Step position: axial (left) and circumferential (right) velocity profiles at  x2 for honeycomb convergent labyrinth seal

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Fig. 33

Step position: axial (left) and circumferential (right) velocity profiles at  x3 for smooth divergent labyrinth seal

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Fig. 34

Step position: axial (left) and circumferential (right) velocity profiles at  x3 for honeycomb divergent labyrinth seal

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