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Research Papers: Flows in Complex Systems

Uncertainty Quantification of Leakages in a Multistage Simulation and Comparison With Experiments

[+] Author and Article Information
Cosimo Maria Mazzoni

Mem. ASME
Osney Thermo-Fluids Laboratory,
Department of Engineering Science,
Oxford University,
Southwell Building, Osney Mead,
Oxford OX2 0DP, UK
e-mail: cosimo.maria.mazzoni@gmail.com

Richard Ahlfeld

Department of Aeronautics,
Imperial College of London,
South Kensington Campus,
London SW7 2AZ, UK
e-mail: ahlfeld.richard@googlemail.com

Budimir Rosic

Mem. ASME
Osney Thermo-Fluids Laboratory,
Department of Engineering Science,
Oxford University,
Southwell Building, Osney Mead,
Oxford OX2 0DP, UK
e-mail: budimir.rosic@eng.ox.ac.uk

Francesco Montomoli

Department of Aeronautics,
Imperial College of London,
South Kensington Campus,
London SW7 2AZ, UK
e-mail: f.montomoli@imperial.ac.uk

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received August 28, 2016; final manuscript received August 25, 2017; published online November 3, 2017. Assoc. Editor: Olivier Coutier-Delgosha.

J. Fluids Eng 140(2), 021110 (Nov 03, 2017) (10 pages) Paper No: FE-16-1554; doi: 10.1115/1.4037983 History: Received August 28, 2016; Revised August 25, 2017

This paper presents a numerical study of the impact of tip gap uncertainties in a multistage turbine. It is well known that the rotor gap can change the gas turbine efficiency, but the impact of the random variation of the clearance height has not been investigated before. In this paper, the radial seals clearance of a datum shroud geometry, representative of steam turbine industrial practice, was systematically varied and numerically tested by means of unsteady computational fluid dynamics (CFD). By using a nonintrusive uncertainty quantification (UQ) simulation based on a sparse arbitrary moment-based approach, it is possible to predict the radial distribution of uncertainty in stagnation pressure and yaw angle at the exit of the turbine blades. This work shows that the impact of gap uncertainties propagates radially from the tip toward the hub of the turbine, and the complete span is affected by a variation of the rotor tip gap. This amplification of the uncertainty is mainly due to the low-aspect ratio of the turbine, and a similar behavior is expected in high pressure (HP) turbines.

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References

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Figures

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Fig. 1

Schematic of model turbine

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Fig. 2

Shroud sealing arrangement

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Fig. 3

Representation of the experimental turbine: (a) representation of the experimental turbine and (b) blade geometry

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Fig. 4

TBLOCK computational domain

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Fig. 5

TBLOCK computational grid

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Fig. 6

TBLOCK—rotor and tip shroud grid structure

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Fig. 7

Measured and predicted total pressure coefficient downstream stators 2 and 3

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Fig. 8

Measured and predicted pitchwise-averaged total pressure coefficient downstream rotors 2 and 3

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Fig. 9

Measured and predicted pitchwise-averaged axial velocity downstream stator 3 and rotor 3

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Fig. 10

Measured and predicted pitchwise-averaged yaw angle downstream stator 2 and rotor 3

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Fig. 11

Predicted pitchwise-averaged total pressure coefficient profiles for different seals clearances

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Fig. 12

Predicted pitchwise averaged yaw angle profiles for different seals clearances

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Fig. 13

Change in turbine efficiency with leakage fraction

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Fig. 14

Probability distribution used as input PDF including optimal Gaussian collocation points

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Fig. 15

Stagnation pressure coefficient distribution and uncertainty

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Fig. 16

Yaw angle variation and standard deviation superimposed

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