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Turbine end-wall aerothermal management with engineered surface structure

Miao, X. (2018). Turbine end-wall aerothermal management with engineered surface structure. (Unpublished Doctoral thesis, City, University of London)

Abstract

Motivated by the enlarged design space and additional flexibility offered by the latest advances in manufacturing techniques, especially Additive Manufacturing (AM), this thesis investigates a novel turbine end-wall aerothermal management method with the engineered surface structures, through closely coupled experi-mental and numerical studies. A 90-degree turning duct and a linear turbine cascade test section were employed for the experimental research in a low-speed wind tunnel. Duct and turbine end-wall heat transfer and cooling effectiveness were measured by transient Infrared Thermography. PIV measurement was conducted to obtain the exit flow field. Computational fluid dynamics (CFD) simulations were performed using ANSYS FLUENT to compliment the experimental findings. The flow solver uses the finite volume method to solve the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations. The k-ω shear stress transport (SST) turbulence model was validated and chosen for all the numerical studies. The secondary flow control principle of the engineered surface structure in the simplified duct is revealed through a detailed investigation of the flow produced by multiple small surface structures. The CFD and PIV measurement results consistently show that addition of the engineered surface structure on end-wall can effectively reduce the magnitude of streamwise vorticity associated with the secondary flow and alleviate its lift-off motion. For turbine cascade applications, it can be observed that the strength of the passage vortex is effectively reduced, and the passage vortex loss core moves closer to the end-wall with the addition of the engineered surface structure. The purge air cooling enhancement by the engineered surface structure is then studied. The purge air cooling flow becomes more attached to the end-wall and covers a larger wall surface area with the added end-wall rib structures. Both experimental and numerical results reveal a consistent trend on improving film cooling effectiveness and net heat flux reduction (NHFR). This novel concept was success-fully demonstrated in a more realistic turbine cascade case. Enhanced cooling effectiveness and net heat flux reduction were obtained from both experimental data and CFD analysis. The additional surface features were proved to be effective in reducing the passage vortex and providing more coolant coverage without introducing additional aerodynamic loss. The overall Net Heat Load Reduction for the 90-degree turning duct and the turbine cascade is increased by 11% and 2% respectively.

Publication Type: Thesis (Doctoral)
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments: Doctoral Theses
Doctoral Theses > School of Mathematics, Computer Science and Engineering Doctoral Theses
School of Mathematics, Computer Science & Engineering > Engineering > Mechanical Engineering & Aeronautics
URI: http://openaccess.city.ac.uk/id/eprint/20405
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