Optimization of blade stacking in the last stage of low-pressure (LP) steam turbines constitutes one of the most delicate and time-consuming parts of the design process. This is the first of two papers focusing on the stacking strategies applied to the last stage guide vane (G0). Following a comprehensive review of the main features that characterize the LP last stage aerodynamics, the three-dimensional (3D) computational fluid dynamics (CFD) code used for the investigation and options related to the modeling of wet steam are described. Aerodynamic problems related to the LP last stage and the principles of 3D stacking are reviewed in detail. In this first paper, the results of a systematic study on an isolated LP stator row are used to elucidate the effects of stacking schemes, such as lean, twist, sweep, and hub profiling. These results show that stator twist not only has the most powerful influence on the reaction variation but it also produces undesirable spanwise variations in angular momentum at stator exit. These may be compensated by introducing a positive stagnation pressure gradient at entry to the last stage.
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Three-Dimensional Blade-Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part I: Three-Dimensional Stacking Mechanisms
John Denton
John Denton
Emeritus Professor
Whittle Laboratory,
Department of Engineering,
University of Cambridge,
North Yorkshire DL84LG, UK
e-mail: jdd1@cam.ac.uk
Whittle Laboratory,
Department of Engineering,
University of Cambridge,
North Yorkshire DL84LG, UK
e-mail: jdd1@cam.ac.uk
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Said Havakechian
John Denton
Emeritus Professor
Whittle Laboratory,
Department of Engineering,
University of Cambridge,
North Yorkshire DL84LG, UK
e-mail: jdd1@cam.ac.uk
Whittle Laboratory,
Department of Engineering,
University of Cambridge,
North Yorkshire DL84LG, UK
e-mail: jdd1@cam.ac.uk
Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 20, 2015; final manuscript received September 10, 2015; published online November 3, 2015. Editor: David Wisler.
J. Eng. Gas Turbines Power. May 2016, 138(5): 052603 (10 pages)
Published Online: November 3, 2015
Article history
Received:
July 20, 2015
Revised:
September 10, 2015
Citation
Havakechian, S., and Denton, J. (November 3, 2015). "Three-Dimensional Blade-Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part I: Three-Dimensional Stacking Mechanisms." ASME. J. Eng. Gas Turbines Power. May 2016; 138(5): 052603. https://doi.org/10.1115/1.4031597
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