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Research Papers

Analysis on the Effect of a Nonuniform Inlet Profile on Heat Transfer and Fluid Flow in Turbine Stages

[+] Author and Article Information
Salvadori Simone, Francesco Martelli

Department of Energy Engineering, University of Firenze, via di Santa Marta, 3 50134 Firenze, Italy

Francesco Montomoli

Whittle Laboratory, University of Cambridge, 1 JJ Thomson Avenue, CB3 0DY, Cambridge, UK

Kam S. Chana1

 QinetiQ, Building A7 Room 2008, Cody Technology Park, Ively Road, Farnborough Hants, GU14 0LX, UK

Imran Qureshi, Tom Povey

Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ, Oxford, UK

1

Present address: Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ, Oxford, UK.

J. Turbomach 134(1), 011012 (May 26, 2011) (14 pages) doi:10.1115/1.4003233 History: Received September 06, 2010; Revised October 15, 2010; Published May 26, 2011; Online May 26, 2011

This paper presents an investigation of the aerothermal performance of a modern unshrouded high-pressure (HP) aero-engine turbine subject to nonuniform inlet temperature profile. The turbine used for this study was the MT1 turbine installed in the QinetiQ turbine test facility based in Farnborough (UK). The MT1 turbine is a full scale transonic HP turbine, and is operated in the test facility at the correct nondimensional conditions for aerodynamics and heat transfer. Datum experiments of aerothermal performance were conducted with uniform inlet conditions. Experiments with nonuniform inlet temperature were conducted with a temperature profile that had a nonuniformity in the radial direction defined by (TmaxTmin)/T¯=0.355, and a nonuniformity in the circumferential direction defined by (TmaxTmin)/T¯=0.14. This corresponds to an extreme point in the engine cycle, in an engine where the nonuniformity is dominated by the radial distribution. Accurate experimental area surveys of the turbine inlet and exit flows were conducted, and detailed heat transfer measurements were obtained on the blade surfaces and end-walls. These results are analyzed with the unsteady numerical data obtained using the in-house HybFlow code developed at the University of Firenze. Two particular aspects are highlighted in the discussion: prediction confidence for state of the art computational fluid dynamics (CFD) and impact of real conditions on stator-rotor thermal loading. The efficiency value obtained with the numerical analysis is compared with the experimental data and a 0.8% difference is found and discussed. A study of the flow field influence on the blade thermal load has also been detailed. It is shown that the hot streak migration mainly affects the rotor pressure side from 20% to 70% of the span, where the Nusselt number increases by a factor of 60% with respect to the uniform case. Furthermore, in this work, it has been found that a nonuniform temperature distribution is beneficial for the rotor tip, contrary to the results found in open literature. Although the hot streak is affected by the pressure gradient across the tip gap, the radial profile (which dominates the temperature profile being considered) is not fully mixed out in passing through the HP stage, and contributes significantly to cooling the turbine casing. A design approach not taking into account these effects will underestimate the rotor life near the tip and the thermal load at midspan. The temperature profile that has been used in both experiments and CFD is the first simulation of an extreme cycle point (more than twice the magnitude of distortion of all previous experimental studies): It represents an engine-take-off condition combined with the full combustor cooling. This research was part of the EU funded Turbine AeroThermal External Flows 2 program.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Segregation effect for wakes and hot streaks

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Figure 2

Schematic of the TTF

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Figure 3

EOTDF profile at the stator inlet

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Figure 4

Comparison of simulated and target profiles

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Figure 5

Computational grid

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Figure 6

Flow expansion within turbine stages

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Figure 7

Isentropic Mach number on the NGV: 10% span

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Figure 8

Isentropic Mach number on the NGV: 50% span

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Figure 9

Isentropic Mach number on the NGV: 90% span

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Figure 10

Static pressure on the rotor blade: 50% span

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Figure 11

Nu number distribution on the stator: 50% span

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Figure 12

Nu number distribution on the rotor: 10% span

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Figure 13

Nu number distribution on the rotor: 50% span

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Figure 14

Nu number distribution on the rotor: 90% span

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Figure 15

Nu number distribution on the casing: EOTDF

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Figure 16

Nu number on the blade pressure side: uniform

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Figure 17

Nu number on the blade pressure side: EOTDF

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Figure 18

Nu number variation on the blade pressure side (uniform data as reference)

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Figure 19

Post-processing planes and probe’s positions

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Figure 20

Absolute Mach number and total pressure distributions in the near plane

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Figure 21

Nondimensional time-resolved absolute total temperature at midspan for uniform inlet

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Figure 22

Nondimensional time-resolved absolute total temperature at midspan for EOTDF

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Figure 23

Time-resolved absolute total temperature variation at midspan (uniform data as reference)

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Figure 24

Nondimensional time-resolved absolute total pressure at midspan for uniform inlet

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Figure 25

Nondimensional time-resolved absolute total pressure at midspan for EOTDF inlet

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