Research Papers

Impact of Severe Temperature Distortion on Turbine Efficiency

[+] Author and Article Information
Paul F. Beard, Thomas Povey

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

Andy Smith

Rolls-Royce PLC,
Turbine Systems,
PCF-1, P.O. Box 31,
Moor Lane,
Derby, DE24 8BJ, UK

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) Division of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 11, 2011; final manuscript received August 15, 2011; published online October 30, 2012. Editor: David Wisler.

J. Turbomach 135(1), 011018 (Oct 30, 2012) (12 pages) Paper No: TURBO-11-1117; doi: 10.1115/1.4006389 History: Received July 11, 2011; Revised August 15, 2011

This paper presents an experimental and computational study of the effect of severe inlet temperature distortion (hot streaks) on the efficiency of the MT1 HP turbine, which is a highly-loaded unshrouded transonic design. The experiments were performed in the Oxford Turbine Research Facility (OTRF) (formerly the TTF at QinetiQ Farnborough): an engine scale, short duration, rotating transonic facility, in which M, Re, Tgas/Twall and N/T01 are matched to engine conditions. The research formed part of the EU Turbine Aero-Thermal External Flows (TATEF II) program. An advanced second generation temperature distortion simulator was developed for this investigation, which allows both radial and circumferential temperature profiles to be simulated. A pronounced profile was used for this study. The system was novel in that it was designed to be compatible with an efficiency measurement system which was also developed for this study. To achieve low uncertainty (bias and precision errors of approximately 1.5% and 0.2% respectively, to 95% confidence), the mass flow rate of the hot and cold streams used to simulate temperature distortion were independently metered upstream of the turbine nozzle using traceable measurement techniques. Turbine power was measured directly with an accurate torque transducer. The efficiency of the test turbine was evaluated experimentally for a uniform inlet temperature condition, and with pronounced temperature distortion. Mechanisms for observed changes in the turbine exit flow field and efficiency are discussed. The data are compared in terms of flow structure to full stage computational fluid dynamics (CFD) performed using the Rolls Royce Hydra code.

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Fig. 1

The Oxford Turbine Research Facility (OTRF)

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Fig. 2

Measured stage inlet temperature profile with: (a) uniform inlet conditions, (b) inlet hot-streak generation

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Fig. 3

Enthalpy-entropy chart showing isentropic and nonadiabatic turbine expansions

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Fig. 4

Rotor exit near plane area-survey results of total pressure, p03, with inlet hot-streaks

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Fig. 5

Rotor exit far plane area-survey results of total pressure, p04, with inlet hot-streaks

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Fig. 6

Vane and rotor computational meshes

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Fig. 7

Distributions of NGV surface isentropic Mach number with and without inlet temperature distortion

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Fig. 9

Radial analysis of the effect of inlet temperature distortion on vane capacity

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Fig. 8

Measured capacity of modern HP vane [25]

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Fig. 10

Calculated differences in radial work function distribution with inlet hot-streaks

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Fig. 11

Attenuation of radial temperature profile by work extraction and flow redistribution/mixing

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Fig. 12

Predicted impact of off-design incidence on rotor performance with EOTDF—differences plotted as changes from case with uniform inlet conditions

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Fig. 13

Generation of streamwise vorticity by gradients in rotor inlet flow-field

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Fig. 14

Computed NGV isentropic Mach number distributions at 50% span with and without inlet hot-streaks

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Fig. 15

Computed profiles of vane inlet and exit total temperature, and computed changes in vane exit whirl angle and Mach number with inlet hot-streaks

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Fig. 16

Computed changes in relative total temperature at rotor inlet with inlet hot-streaks

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Fig. 17

Computed changes in relative total pressure at rotor inlet with inlet hot-streaks




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