Flow Control and Shape Optimization of Intermediate Turbine Ducts for Turbofan Engines
Doctoral thesis, 2008

Demands on improved efficiency, reduced emissions and lowered noise levels cause a strive towards high by-pass ratios of commercial turbofan engines. This results in an increased radial offset between the high- and low-pressure turbines. Thus the design of the intermediate turbine duct connecting the two turbines becomes more challenging. In this thesis the main focus is to explore techniques that enable design of turbine ducts with reduced length, larger radial offset or increased diffusion, so-called aggressive ducts. Response surface methodology and design of experiments techniques have been adopted to perform duct shape optimization based on CFD. A novel geometry parameterization suitable for both axisymmetric and non-axisymmetric endwalls, based on axial orthogonal polynomials and circumferential harmonics, has been introduced. Results show that shape optimization has the potential to reduce duct loss significantly. Flow control could be applied to avoid separation in highly aggressive ducts. Vortex generators are well-known, reliable and cost-effective passive flow control devices and have therefore been used in this work. Resolving the small scales of vortex generators requires fine grids and time consuming computations. Therefore a computational body-force model was developed and validated. The baseline separation in a very aggressive turbine duct was suppressed by an optimized vortex generator installation, defined using the body-force model. Steady RANS analyzes with different two-equation eddy viscosity models have been used to assess the aerothermal behavior of a state-of-the-art turbine duct. Detailed experimental data has been used to validate the CFD approach adopted throughout this work.

CFD

response surface methodology

intermediate turbine duct

vortex generators

turbine intermediate case

endwall contouring

turbine center frame

body-force model

shape optimization

mid-turbine frame

flow control

VG
Opponent: Dr. Robert J. Miller, Senior Lecturer, Whittle Laboratory, Department of Engineering, Cambridge University, England

Author

Fredrik Wallin

Chalmers, Applied Mechanics, Fluid Dynamics

Experimental and Numerical Investigation of an Aggressive Intermediate Turbine Duct: Part 1−Flowfield at Design Inlet Conditions

Paper AIAA-2008-7055, 26th AIAA Applied Aerodynamics Conference, Honolulu, August 18-21, 2008,; (2008)

Paper in proceeding

A Tuning-free Body-force Vortex Generator Model

44th AIAA Aerospace Sciences Meeting Proceedings (2006),; (2006)

Paper in proceeding

Experimental and Numerical Investigation of an Aggressive Intermediate Turbine Duct: Part 2−Flowfield under Off-Design Inlet Conditions

Collection of Technical Papers - AIAA Applied Aerodynamics Conference,; (2008)

Paper in proceeding

Intermediate Turbine Duct Design and Optimization

25th Congress of the International Council of the Aeronautical Sciences (ICAS),; (2006)

Paper in proceeding

Non-axisymmetric Endwall Shape Optimization of an Intermediate Turbine Duct

18th ISABE Conference,; (2007)

Paper in proceeding

Response Surface-based Transition Duct Shape Optimization

2006 Proceedings of ASME Turbo Expo: Power for Land, Sea, and Air,; (2006)

Paper in proceeding

Design of an Aggressive Flow-controlled Turbine Duct

ASME Turbo Expo 2008,; (2008)

Paper in proceeding

Subject Categories

Fluid Mechanics and Acoustics

ISBN

978-91-7385-205-0

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 2886

VG

Opponent: Dr. Robert J. Miller, Senior Lecturer, Whittle Laboratory, Department of Engineering, Cambridge University, England

More information

Created

10/6/2017