Research Papers

Loss Audit of a Turbine Stage

[+] Author and Article Information
Sungho Yoon

GE Global Research,
Munich 85748, Germany
e-mail: yoons@ge.com

Thomas Vandeputte

GE Global Research,
Niskayuna, NY 12309

Hiteshkumar Mistry

GE Global Research,
Bangalore 560 006, India

Jonathan Ong

GE Global Research,
Munich 85748, Germany

Alexander Stein

GE Power & Water,
Greenville, SC 29615

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received November 4, 2015; final manuscript received November 28, 2015; published online January 20, 2016. Editor: Kenneth C. Hall.

J. Turbomach 138(5), 051004 (Jan 20, 2016) (9 pages) Paper No: TURBO-15-1247; doi: 10.1115/1.4032138 History: Received November 04, 2015; Revised November 28, 2015

In order to achieve high aerodynamic efficiency of a turbine stage, it is crucial to identify the source of aerodynamic losses and understand the associated loss generation mechanisms. This helps a turbine designer to maximize the performance of the turbine stage. It is well known that aerodynamic losses include profile, endwall, cooling/mixing loss, leakage, and trailing edge loss components. However, it is not a trivial task to separate one from the others because different loss sources occur concurrently and they interact with each other in a machine. Consequently, designers tend to rely on various empirical correlations to get an approximate estimate of each aerodynamic loss contribution. In this study, a systematic loss audit of an uncooled turbine stage has been undertaken by conducting a series of numerical experiments. By comparing entropy growth across the turbine stage, aerodynamic losses are broken down within the stator, rotor, and interblade row gap. Furthermore, losses across each blade row are broken down into profile, leakage, endwall, and trailing edge losses. The effect of unsteady interaction due to the relative motion of the stator and the rotor was also identified. For the examined turbine stage, trailing edge losses of the rotor were dominated, contributing to more than a third of the total aerodynamic loss. The profile loss across the stator and the rotor, unsteady loss between the stator and the rotor, and the stator endwall loss were also identified to be the significant loss sources for this turbine stage. The design implications of the findings are discussed.

Copyright © 2016 by ASME
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Fig. 1

Effect of leakage flow on the accumulated viscous loss (Zlatinov et al. [4]): (a) change in viscous loss and (b) entropy generation rate

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Fig. 2

Loss audit using entropy generation rate (Pullan et al. [6]): (a) zones for loss audit and (b) loss audit for three NGVs

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Fig. 3

Schematic of computational domain

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Fig. 4

Grid density of the stator geometry

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Fig. 5

Accumulation of aerodynamic loss in the axial distance (no leakage flow)

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Fig. 6

Accumulation of aerodynamic loss in the axial distance with respect to numerical experiments across the stator

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Fig. 7

Change in the stator efficiency due to numerical experiments

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Fig. 8

Entropy generation rate on a quasi-orthogonal plane at 90% chord: (a) no endwall loss and profile loss and (b) datum

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Fig. 9

Entropy generation rate on a blade-to-blade plane which is located at 90% span: (a) datum, (b) no profile loss, and (c) zoomed view near the trailing edge, no profile loss

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Fig. 10

Entropy generation rate at two radial span positions: (a) near the tip and (b) near the hub

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Fig. 11

Loss audit in terms of the percentage of the total loss (total = 100%)

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Fig. 12

Accumulation of aerodynamic loss in the axial distance for both steady and time-averaged unsteady simulations

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Fig. 13

Comparison of the stator efficiency between the steady calculation and the time-averaged unsteady calculation: (a) 95% chord and (b) downstream of the stator

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Fig. 14

Instantaneous entropy across the stator in the unsteady CFD (near the hub)

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Fig. 15

Relative Mach number at the rotor trailing edge

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Fig. 16

Entropy generation rate on blade-to-blade surface: (a) inner span (the top plot is based on unsteady CFD, whereas the bottom plot is based on steady CFD) and (b) outer span (the top plot is based on unsteady CFD, whereas the bottom plot is based on steady CFD)

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Fig. 17

Entropy generation rate on a quasi-orthogonal plane (102% chord)




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