Research Papers

Loss Reduction in a 1.5 Stage Axial Turbine by Computer-Driven Stator Hub Contouring

[+] Author and Article Information
Hayder M. B. Obaida

Middle Technical University,
Engineering Technical College,
Baghdad, 7F7P+JG, Iraq
e-mail: Dr.Haydermahdi@mtu.edu.iq

Aldo Rona

Department of Engineering,
University of Leicester,
Leicester, LE1 7RH, UK
e-mail: ar45@leicester.le.ac.uk

J. Paul Gostelow

Fellow ASME
Department of Engineering,
University of Leicester,
Leicester, LE1 7RH, UK
e-mail: jpg7@leicester.ac.uk

1Corresponding author.

Manuscript received February 9, 2017; final manuscript received December 11, 2018; published online January 29, 2019. Assoc. Editor: Rolf Sondergaard.

J. Turbomach 141(6), 061009 (Jan 29, 2019) (11 pages) Paper No: TURBO-17-1028; doi: 10.1115/1.4042305 History: Received February 09, 2017; Revised December 11, 2018

Improvements in stage isentropic efficiency and reductions in total pressure loss are sought in a 1.5 stage axial turbine. This is representative of power generation equipment used in thermal power cycles, which delivers about 80% of the 20 × 1012 kWh world-wide electricity. Component-level improvements are therefore timely and important toward achieving carbon dioxide global emission targets. Secondary flow loss reduction is sought by applying a nonaxisymmetric endwall design to the turbine stator hub. A guide groove directs the pressure side branch of the horseshoe vortex away from the airfoil suction side, using a parametric endwall hub surface, which is defined as to obtain first-order smooth boundary connections to the remainder of the passage geometry. This delays the onset of the passage vortex and reduces its associated loss. The Automatic Process and Optimization Workbench (apow) generates a Kriging surrogate model from a set of Reynolds-averaged Navier–Stokes simulations, which is used to optimize the hub surface. The three-dimensional steady Reynolds-averaged Navier–Stokes model with an axisymmetric hub is validated against reference experimental measurements from the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen. Comparative computational fluid dynamics (CFD) predictions with an optimized nonaxisymmetric hub show a decrease in the total pressure loss coefficient and an increase in the isentropic stage efficiency at and off design conditions.

Copyright © 2019 by ASME
Your Session has timed out. Please sign back in to continue.


Denton, J. D. , 1993, “The 1993 IGTI Scholar Lecture: Loss Mechanisms in Turbomachines,” ASME J. Turbomach., 115(4), pp. 621–656. [CrossRef]
Denton, J. , and Pullan, G. , 2012, “A Numerical Investigation Into the Sources of Endwall Loss in Axial Flow Turbines,” ASME Paper No. GT2012-69173.
Kawase, M. , and Rona, A. , 2018, “Multi-Passage Time-Resolved CFD Analysis of Rotor Tip Stall Inception and Passive Control in a Highly-Loaded Axial Compressor,” Royal Aeronautical Society Biennial Applied Aerodynamics Research Conference “The Future of Aviation,” Bristol, UK, July 24–26, Paper No. T.2.
Harvey, N. , Brennan, G. , Newman, D. , and Rose, M. , 2002, “Improving Turbine Efficiency Using Non-Axisymmetric End Walls: Validation in the Multi-Row Environment and With Low Aspect Ratio Blading,” ASME Paper No. GT2002-30337.
Harvey, N. W. , 2008, “Some Effects of Non-Axisymmetric End Wall Profiling on Axial Flow Compressor Aerodynamics—Part I: Linear Cascade Investigation,” ASME Paper No. GT2008-50990.
Harvey, N. W. , and Offord, T. P. , 2008, “Some Effects of Non-Axisymmetric End Wall Profiling on Axial Flow Compressor Aerodynamics—Part II: Multi-Stage HPC CFD Study,” ASME Paper No. GT2008-50991.
Heinichen, F. , Gümmer, V. , Plas, A. , and Schiffer, H. P. , 2011, “Numerical Investigation of the Influence of Non-Axisymmetric Hub Contouring on the Performance of a Shrouded Axial Compressor Stator,” CEAS Aeronaut. J., 2(1–4), pp. 89–98. [CrossRef]
Hergt, A. , Dorfner, C. , Steinert, W. , Nicke, E. , and Schreiber, H.-A. , 2011, “Advanced Nonaxisymmetric Endwall Contouring for Axial Compressors by Generating an Aerodynamic Separator—Part II: Experimental and Numerical Cascade Investigation,” ASME J. Turbomach., 133(2), p. 021027. [CrossRef]
Hergt, A. , Klinner, J. , Steinert, W. , Dorfner, C. , and Nicke, E. , 2011, “Detailed Flow Analysis of a Compressor Cascade With a Non-Axisymmetric Endwall Contour,” Ninth European Conference on Turbomachinery, Istanbul, Turkey, Mar. 21–25, Paper No. A095.
Zimmermann, T. W. , Curkovic, O. , Wirsum, M. , Fowler, A. , and Patel, K. , 2016, “Comparison of 2D and 3D Airfoils in Combination With Non Axisymmetric End Wall Contouring—Part 1: Experimental Investigations,” ASME Paper No. GT2016-56494.
Kim, I. , Kim, J. , Cho, J. , and Kang, Y.-S. , 2016, “Non-Axisymmetric Endwall Profile Optimization of a High-Pressure Transonic Turbine Using Approximation Model,” ASME Paper No. GT2016-57970.
Reutter, O. , Hervé, S. , and Nicke, E. , 2013, “Automated Optimization of the Non-Axisymmetric Hub Endwall of the Rotor of an Axial Compressor,” Tenth European Conference on Turbomachinery, Lappeenranta, Finland, Apr. 15–19, Paper No. ETC2013-025.
Dunn, D. , Snedden, G. , and Von Backström, T. W. , 2010, “Experimental Investigation Into the Unsteady Effects on Non-Axisymmetric Turbine Endwall Contouring,” 7th South African Conference on Computational and Applied Mechanics SACAM 2010, Pretoria, South Africa, Jan. 10–13, pp. 424–434.
Hartland, J. , Gregory-Smith, D. , and Rose, M. , 1998, “Non-Axisymmetric Endwall Profiling in a Turbine Rotor Blade,” ASME Paper No. 98-GT-525.
Bagshaw, D. , Ingram, G. , Gregory-Smith, D. , Stokes, M. , and Harvey, N. , 2008, “The Design of Three-Dimensional Turbine Blades Combined With Profiled Endwalls,” Proc. Inst. Mech. Eng., Part A, 222(1), pp. 93–102. [CrossRef]
Schuepbach, P. , Abhari, R. , Rose, M. , Germain, T. , Raab, I. , and Gier, J. , 2010, “Improving Efficiency of a High Work Turbine Using Nonaxisymmetric Endwalls—Part II: Time-Resolved Flow Physics,” ASME J. Turbomach., 132(2), p. 021008. [CrossRef]
Snedden, G. , 2011, “The Application of Non-Axisymmetric Endwall Contouring in a 1½ Stage, Rotating Turbine,” Ph.D. dissertation, Durham University, Durham, UK.
Nagel, M. G. , and Baier, R.-D. , 2005, “Experimentally Verified Numerical Optimization of a Three-Dimensional Parametrized Turbine Vane With Nonaxisymmetric End Walls,” ASME J. Turbomach., 127(2), pp. 380–387. [CrossRef]
Polynkin, A. , Toropov, V. , and Shahpar, S. , 2010, “Multidisciplinary Optimization of Turbomachinery Based on Metamodel Built by Genetic Programming,” AIAA Paper No. 2010-9397.
Shahpar, S. , Caloni, S. , and de Prieëlle, L. , 2014, “Automatic Design Optimization of Profiled Endwalls Including Real Geometrical Effects to Minimize Turbine Secondary Flows,” ASME Paper No. GT2014-26628.
Kang, Y.-S. , Rhee, D.-H. , Kim, C.-T. , and Cha, B.-J. , 2013, “Aerodynamic Optimization of Axial Turbine Tip Cavity With Approximation Model,” ASME Paper No. TBTS2013-2079.
Obaida, H. M. , Kawase, M. , Rona, A. , and Gostelow, J. P. , 2016, “Some Perspectives on the Treatment of Three-Dimensional Flows on Axial Compressor Blading,” ASME Paper No. GT2016-57617.
Gourdain, N. , and Leboeuf, F. , 2009, “Unsteady Simulation of an Axial Compressor Stage With Casing and Blade Passive Treatment,” ASME J. Turbomach., 131(2), p. 021013. [CrossRef]
Walraevens, R. E., and Gallus, H. E., 1995, “Stator-Rotor-Stator Interaction in an Axial Flow Turbine and its Influence on Loss Mechanisms,” Paper No. AGARD CP 571. http://publications.rwth-aachen.de/record/101899
Volmar, T. , Brouillet, B. , Gallus, H. E. , and Benetschik, H. , 1998, “Time Accurate 3D Navier-Stokes Analysis of a 1 1/2 Stage Axial Flow Turbine,” AIAA Paper No. 98-3247.
Gallus, H. E. , Zeschky, J. , Weskamp, K. , and Zebner, H. , 1990, “Experimental and Numerical Investigations on the Viscous Flow Through an Axial-Flow Turbine Stage,” Interfluid 1st International Congress on Fluid Handling Systems, Guga-Halle Essen, Germany, Sept. 10–14, pp. 856–869.
Uroić, T. , Šojat, B. , and Jasak, H. , 2017, “Development of an Automated Process for Turbine Blade Optimisation,” VII International Conference on Computational Models for Coupled Problems in Science and Engineering, Coupled Problems, Rhodes Island, Greece, June 12–14, pp. 859–869.
Yao, J. , Davis, R. L. , Alonso, J. J. , and Jameson, A. , 2002, “Massively Parallel Simulation of the Unsteady Flow in an Axial Turbine Stage,” AIAA J. Propul. Power, 18(2), pp. 465–471.
Walraevens, R. E., Gallus, H. E., Jung, A. R., Mayer, J. F., and Setter, H., 1998, “Experimental and Computational Study of the Unsteady Flow in a 1.5 Stage Axial Turbine With Emphasis on the Secondary Flow in the Second Stator,” ASME Paper No. 98-GT-254.
Jasak, H. , and Beaudoin, M. , 2011, “OpenFOAM Turbo Tools: From General Purpose CFD to Turbomachinery Simulations,” ASME Paper No. AJK2011-05015.
ANSYS, 2013, ANSYS ICEM CFD Help Manual, ANSYS, Canonsburg, PA.
Schwer, L. E. , 2008, “Is Your Mesh Refined Enough? Estimating Discretization Error Using GCI,” 7th German LS-DYNA Forum 2008, Bamberg, Germany, Sept. 30–Oct. 1, pp. 45–54.
Roache, P. J. , 1994, “Perspective: A Method for Uniform Reporting of Grid Refinement Studies,” ASME J. Fluids Eng., 116(3), pp. 405–413. [CrossRef]
Reis, A. J. F. , 2013, “Validation of NASA Rotor 67 With OpenFOAM's Transonic Density-Based Solver,” Ph.D. dissertation, New University of Lisbon, Lisbon, Portugal.
Obaida, H. M. , Kadhim, H. T. , Rona, A. , Leschke, K. , and Gostelow, J. P. , 2017, “A Numerical Study of Secondary Flows in a 1.5 Stage Axial Turbine Guiding the Design of Non-Axisymmetric Hub,” ASME Paper No. GT2017-65251.
Kadhim, H. , Rona, A. , Gostelow, J. P. , and Leschke, K. , 2018, “Optimization of the Non-Axisymmetric Stator Casing of a 1.5 Stage Axial Turbine,” Int. J. Mech. Sci., 136, pp. 503–514. [CrossRef]


Grahic Jump Location
Fig. 5

Radial distribution of meridional, circumferential, and absolute velocity 0.142 s behind the rotor airfoil row

Grahic Jump Location
Fig. 6

Radial distribution of yaw angle at 0.142 s behind the rotor airfoil row

Grahic Jump Location
Fig. 4

Spanwise profiles of circumferential and meridional velocity components traversed 0.142 s downstream of the rotor trailing edge. Predictions using three progressively finer computational meshes.

Grahic Jump Location
Fig. 3

Radial distribution of meridional velocity component 2.3 s upstream of the stator 1 airfoil row

Grahic Jump Location
Fig. 2

Schematic of the 1.5 stage turbine flow passage

Grahic Jump Location
Fig. 1

Schematic of the turbine stage on the cascade plane [29]. All lengths in mm.

Grahic Jump Location
Fig. 7

Flow visualization near the stator 1 pressure side leading edge showing the separation of the oncoming hub wall boundary layer on approach to the vane

Grahic Jump Location
Fig. 8

Flow visualization over the stator 1 axisymmetric hub, by ribbons

Grahic Jump Location
Fig. 15

Relative difference between Kriging surrogate surface with 100% of the test data and regenerated Kriging surrogate using 90% of the test data

Grahic Jump Location
Fig. 9

Automatic Process and Optimization Workbench flow diagram

Grahic Jump Location
Fig. 10

Inflating the upstream stator airfoil profile to generate the groove path line

Grahic Jump Location
Fig. 11

Effect of changing the maximum groove depth position from 60% to 80% of the total groove length on the groove depth

Grahic Jump Location
Fig. 12

Nonaxisymmetric upstream stator hub surface imported in ICEM CFD as a NURBS surface

Grahic Jump Location
Fig. 13

Kriging surrogate surface for optimization task 1

Grahic Jump Location
Fig. 14

Kriging surrogate surface for optimization task 2

Grahic Jump Location
Fig. 17

Radial distribution of meridional, circumferential, and absolute velocity 0.142 s behind the upstream stator

Grahic Jump Location
Fig. 16

Visualization of near-surface flow over the upstream stator hub showing the pressure side branch of the horseshoe vortex running through the apow optimized hub groove

Grahic Jump Location
Fig. 18

Iso-levels of total pressure loss coefficient predicted with an axisymmetric hub, 0.142 s downstream of the rotor exit

Grahic Jump Location
Fig. 19

Iso-levels of total pressure loss coefficient predicted with a contoured hub, 0.142 s downstream of the rotor exit

Grahic Jump Location
Fig. 20

Radial distribution of mass-averaged total pressure loss coefficient 0.142 s behind the rotor airfoil row, with an axisymmetric and a contoured upstream stator hub

Grahic Jump Location
Fig. 21

1.5 stage turbine characteristic line with flow simulations shown by dots

Grahic Jump Location
Fig. 22

Predicted stage total pressure loss coefficient with an axisymmetric and a contoured upstream stator hub at design and off-design

Grahic Jump Location
Fig. 23

Predicted stage isentropic efficiency with an axisymmetric and a contoured turbine stator hub at design and off-design



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In