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Title: CFD Predictions of Gas Turbine Full-Coverage Film Cooling
Author: Yusop, Nadiahnor Md
ISNI:       0000 0001 3576 3639
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2007
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The present study aims at conducting a numerical investigation of the classic film cooling scheme of transpiration film cooling and effusion film cooling for validation through computational methods. Steady-state simulations were performed and the flow was considered incompressible with low turbulence. The CFD package FLUENT 6.2.16 was used to solve the Navier-Stokes equations numerically, and the pre-processor, Gambit 2.2.30, was used to generate the required grid. The research aims at perfonning computational predictions on the film cooling performance and the aerodynamics aspect of flat plate film cooling ·on the transpiration and effusion film cooling. It was determined that the proposed scheme and type of geometry, coupled with the hybrid mesh generation, can validate the classic experimental results. with reasonable agreement. Computational predictions on the transpiration film cooling have shown that different boundary conditions used for the porous media may lead to different results, whether it is over-prediction or under-prediction results in comparison with the experimental data. It has been observed for the effusion film cooling, on the case of co-flow coolant , . ejection into the mainstream, that the adiabatic film cooling effectiveness continuously increases with the axial distance towards the leading edge where the flow of the coolant is fully-developed. Furthermore, the streamwise cooling uniformity was better than in the upstream region at the middle region of the test wall. In contrast, the adiabatic film cooling effectiveness for the opposed flow coolant ejection into the mainstream flow was gradually decreasing with the axial distance. Coflow coolant ejection into the mainstream has provide better cooling effectiveness but the oppose flow coolant ejection from the cooling holes has proved to be good aerodynamics in protecting the adjacent wall due to the large area of the film cooling coverage of the combustor wall. The present study was concerned only with the downstream effectiveness aspect on the performance of the coolant mass flow on the geometrical parameters effects; for transpiration film cooling - the pore size, and effusion film cooling - hole diameter, film cooling hole arrangement, number of holes, inclination and orientation of cooling hole with respect to the mainstream flow. The performance related to the heat transfer coefficient and conjugate heat transfer is a prospective topic for future studies. Advanced and innovative cooling techniques are essential in order to improve the efficiency and output power of the gas turbines. The CFD predictions performed have utilised a scalar tracer gas in the coolant flow and has been very effective at visualizing the coolant to the mainstream mixing phenomenon, determining the boundary layer development and directly predicting the adiabatic film cooling effectiveness. Current methods in determining the film cooling effectiveness using the scalar tracer gas concentration facilitate the future study on the conjugate heat transfer pred,iction where the temperature profiles cannot be used because conjugate heat transfer is highly affected by the effect ofthe temperature in the system. The technique· of providing an alternative method using the heat and mass transfer analogy in quantify the cooling effectiveness combines the advantages of using a scalar tracer gas in determining the cooling effectiveness and also provide clear insight into the film cooling structure in the cooling hole and coolant interaction in the mainstream when the experimental method is at 'off-limit'. The results of the present investigations performed were used to validate the computation model. Therefore, this study is of value for those interested in gas turbine cooling.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available