NUMERICAL CALCULATION OF INTERNAL COOLING, TURBINE BLADE

PhD student: Jonas Bredberg
jonas.bredberg@volvo.com
Supervisor: Lars Davidson
lada@chalmers.se
Cooperation: GTC
Sponsors: STEM, ALSTOM Power, Volvo Aero Corp.
Publications: [1-11], see reference below
Start of project: spring 1997
End of project: June 2002


THE PROJECT
In recent years there have been an increased attention toward more complicated turbulence and heat transfer models in predicting the characteristic of turbomachinery. This have followed from numerous experimental tests where it have been shown that contemporary models (such as eddy-visocosity models) fails to predict the complicated flow behaviour within the internal structure of rotating turbomachinery.
 
The economical savings by increasing the turbine entry temperature (TET), is significant. An increase in TET could be made possible by accurately predict the internal cooling. Research on internal cooling is thus of great importance for gas turbine industry.
 
The internal flow of a rotorblade is generally influenced by rotational effects (Coriolis, inertial) and temparture effects (buoyancy) in addition to complex geometry (turbulators, bends). All these effects can not be modeled through an eddy-viscoisty model, and necessitate a second order closure, RSTM or ARSM.
 
NUMERICAL METHOD
In this project the main focus will be to understanding the physics, with the aid of state of the art turbulence models. The complexity of the geometry will be kept at an elementary level, although incorporating the characteristics of the internal structure of a rotor blade. A number of different turbulence models are used including EARSMs (Gatski and Speziale, Wallin and Johansson) and two-equation models (mainly Wilcox based). The near-wall behaviour, which is of vital importance for heat transfer, is modelled using either an one- equation model (Wolfshtein) or a low-Reynolds number two-equation model. A domestic finite volume code (CALC-BFC) will be used, which utilize non-orthogonal co-located grid, cartesian velocities and SIMPLEC pressure-velocity correlation.
 
Initial (up until spring -98) only 2-D calculations on rib-roughened channel were made using a 2-D version of the EARSM code and the Boussinesq based EVMs, in order to understand basic phyics. Later (autumn -98) a visit was attended at UMIST, Manchester (Prof. Launders group) where the calculations were extended to 3-D. During spring/summer -99 the licentiate was written and presented. As for now (autumn -00) computations are made on rib-roughened u-bends, using the most promising and efficient turbulence model tested previously. Research is also being made on modifications and improvements to these models. A 64-processor Origin 2000 Silicon Graphics machine is used for the computations.
 
This project is supported by Statens Energi Myndighet, Alstom Power and Volvo Aero Corporation
 

 
REFERENCES
 
- click to view postscript file
 
  1. Bredberg, J. and Davidson, L., Case 7.2: Two-Dimensional Flow and Heat Transfer over a Smooth Wall Roughened with Squared Ribs, 7th ERCOFTAC/IAHR Workshop on Refined Turbulence Modelling, UMIST, Manchester, UK, May 28/29th 1998, UMIST, Manchester, UK
     
  2. Bredberg, J. and Davidson, L., Prediction of Flow and Heat Transfer in a Stationary 2-D Rib Roughened Passage Using Low-Re Turbulent Models, 3:rd IMECHE Conference on Turbomachinery, London, UK, March 2/5th 1999, London, UK.
     
  3. Bredberg, J., Prediction of Flow and Heat Transfer Inside Turbine Blades using EARSM, k-epsilon, and k-omega Turbulence Models, Report 99/3, thesis of Lic. of Engng, 1999, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenborg, Sweden
     
  4. Bredberg, J., Davidson, L. and Iacovides, H., Comparison of Near-Wall Behavior and its Effect on Heat Transfer for k-w and k-e Turbulence Models in Rib-roughened 2D Channels, 3:rd International Symposium on Turbulence, Heat and Mass Transfer, Nagoya, Japan, April 2/6th 2000, Nagoya, Japan.
     
  5. Bredberg, J., On the Wall Boundary Condition for Turbulence Models, Report 00/4, 2000, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, Gothenborg, Sweden
     
  6. Bredberg, J., Davidson, L. and Peng S-H., On the Wall Boundary Condition for Computing Turbulent Heat Transfer with k-w Models, The 2000 ASME International Mechanical Engineering Congress & Exposition, Walt Disney World Dolphin, Orlando, Florida, Nov 5-10th 2000, Orlando, USA
     
  7. Bredberg, J., "On Two-equation Eddy-Viscosity Models" Report 01/8, Department of Thermo and Fluid Dynamics, Chalmers University of Technology, 2001.
     
  8. Bredberg, J., "Turbulence Modelling for Internal Cooling of Gas-Turbine Blades", PhD thesis, Dept. of Thermo and Fluid Dynamics, Chalmers University of Technology, Göteborg, 2002.
     
  9. J. Bredberg and L. Davidson
    "Prediction of turbulent heat transfer in stationary and rotating U-ducts with rib roughened walls", "Engineering Turbulence Modelling and Experiments 5", pp. 801--810, W. Rodi and N. Fueyo (Eds.), Elsevier, 2002.
     
  10. J. Bredberg, S-H. Peng and L. Davidson
    "An Improved k-omega Turbulence Model Applied to Recirculating Flows", Int. J. Heat and Fluid Flow Vol. 23, No. 6, pp. 731-743, 2002
     
  11. J. Bredberg and L. Davidson
    "Low-Reynolds Number Turbulence Models: An Approach for Reducing Mesh Sensitivity", J. of Fluid Engineering Vol. 126, No. 1, pp. 14-21, 2004
     

 

 


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