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Research Papers

Leading Edge Shielding Concept in Gas Turbines With Can Combustors

[+] Author and Article Information
Ioanna Aslanidou

e-mail: ioanna.aslanidou@eng.ox.ac.uk

Budimir Rosic

e-mail: budimir.rosic@eng.ox.ac.uk
Osney Laboratory,
University of Oxford,
Osney Mead,
Oxford, OX2 0ES, UK

Vasudevan Kanjirakkad

University of Sussex,
Brighton, BN1 9RH, UK
e-mail: v.kanjirakkad@sussex.ac.uk

Sumiu Uchida

Mitsubishi Heavy Industries Ltd.,
Takasago R & D Center,
Takasago, 676-8686, Japan
e-mail: sumiu_uchida@mhi.co.jp

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received March 16, 2012; final manuscript received August 23, 2012; published online November 2, 2012. Editor: David Wisler.

J. Turbomach 135(2), 021019 (Nov 02, 2012) (9 pages) Paper No: TURBO-12-1026; doi: 10.1115/1.4007514 History: Received March 16, 2012; Revised August 23, 2012

The remarkable developments in gas turbine materials and cooling technologies have allowed a steady increase in combustor outlet temperature and, hence, in gas turbine efficiency over the last half century. However, the efficiency benefits of higher gas temperature, even at the current levels, are significantly offset by the increased losses associated with the required cooling. Additionally, the advancements in gas turbine cooling technology have introduced considerable complexities into turbine design and manufacture. Therefore, a reduction in coolant requirements for the current gas temperature levels is one possible way for gas turbine designers to achieve even higher efficiency levels. The leading edges of the first turbine vane row are exposed to high heat loads. The high coolant requirements and geometry constraints limit the possible arrangement of the multiple rows of film cooling holes in the so-called showerhead region. In the past, investigators have tested many different showerhead configurations by varying the number of rows, inclination angle, and shape of the cooling holes. However, the current leading edge cooling strategies using showerheads have not been shown to allow a further increase in turbine temperature without the excessive use of coolant air. Therefore, new cooling strategies for the first vane have to be explored. In gas turbines with multiple combustor chambers around the annulus, the transition duct walls can be used to shield, i.e., to protect, the first vane leading edges from the high heat loads. In this way, the stagnation region at the leading edge and the showerhead of film cooling holes can be completely removed, resulting in a significant reduction in the total amount of cooling air that is otherwise required. By eliminating the showerhead the shielding concept significantly simplifies the design and lowers the manufacturing costs. This paper numerically analyzes the potential of the leading edge shielding concept for cooling air reduction. The vane shape was modified to allow for the implementation of the concept and nonrestrictive relative movement between the combustor and the vane. It has been demonstrated that the coolant flow that was originally used for cooling the combustor wall trailing edge and a fraction of the coolant air used for the vane showerhead cooling can be used to effectively cool both the suction and the pressure surfaces of the vane.

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References

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Figures

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Fig. 1

Cross section of an industrial gas turbine (Mitsubishi Heavy Industries Ltd [8])

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Fig. 2

Computational flow domain of the combustor wall and first vane leading edge and y vorticity (left), and static pressure contours (right) at the cylindrical leading edge [10]

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Fig. 3

Computational domain geometry (duplicated here for clarity) with details of leakage slots and the transition piece wall trailing edge cooling slot

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Fig. 4

Computational mesh

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Fig. 5

Computational domain geometry (duplicated here for clarity) with details of leakage slots and the combustor wall trailing edge cooling slots for the new shielded vane

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Fig. 6

Original and shielded vane

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Fig. 7

Surface Mach number and normalized pressure distribution of the original vane with no upstream obstruction and a novel shielded design at 50% span

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Fig. 8

Combustor wall cooling slot design strategy

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Fig. 9

Combustor wall cooling slot design

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Fig. 10

Adiabatic effectiveness on the vane surface; coolant mass flow 1.3% of passage inlet

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Fig. 11

Adiabatic effectiveness on the vane surface with a 3 mm displacement to the pressure side

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Fig. 12

Adiabatic effectiveness on the vane surface with a 3 mm displacement to the suction side

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Fig. 13

Coolant used for each slot for the centered and circumferentially displaced cases

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Fig. 14

Details of the datum case and the shielded vane design

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Fig. 15

Normalized temperature distribution of coolant through the hub leakage slot: datum case

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Fig. 16

Normalized temperature distribution of coolant through the hub leakage slot: shielded case

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Fig. 17

Static pressure field and secondary flow at the hub

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Fig. 18

Nondimensional streamwise vorticity at the casing

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Fig. 19

The Q criterion isosurface in the datum and the shielded case

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Fig. 20

Yaw angle 15 mm downstream of the trailing edge for the original and the new shielded vane

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Fig. 21

Total pressure loss coefficient 15 mm downstream of the trailing edge for the original and the new shielded vane

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