An experimental investigation into combined film and internal cooling of turbine blades
Lead Research Organisation:
University of Bath
Department Name: Mechanical Engineering
Abstract
Need:
The push for higher efficiencies in modern gas turbine engines has led to ever-increasing Turbine Entry Temperature (TETs). High pressure turbine blades now operate in an environment where the surrounding gas temperature exceeds the melting point of the materials from which the blades are made. To combat this, air from the compressor section of the engine is bled off and used to cool the blades. Two cooling techniques are employed to prevent damage to the blade from the high TETs: film cooling, where a thin film of coolant is introduced to the surface of the blade to reduce the driving-temperature for heat transfer; and internal cooling, where coolant is passed through a series of passages within the blade to convect heat from the internal surfaces.
Experimental research into turbine blade cooling has predominately treated film cooling and internal cooling as separate topics. This approach fails to capture conjugate heat transfer effects and the resulting impact on the component temperature distribution. The consequence of this is that blades are often conservatively overcooled at the expense of engine efficiency. Experimental data that couples the film and internal cooling would provide greater confidence in blade temperature predictions, reducing the need for superfluous use of coolant and lowering the risk of costly re-design of blades with inadequate cooling.
Aim:
The aim is to "fundamentally explore the heat transfer in film and internally cooled gas turbine blades through the use of novel, highly accurate experimental techniques". The objectives established to meet this aim are to:
1. Design and manufacture a modular test facility to model the heat transfer in a simplified portion of a cooled gas turbine blade.
2. Use IR thermography to obtain heat transfer coefficients from transient heat transfer experiments. This will provide important data for application of the matched-Biot technique.
3. Implement the matched-Biot technique to obtain non-dimensional surface temperature profiles from steady-state heat transfer experiments.
4. Use the CO2-PLIF and V3V technologies to provide detail on the fundamental fluid dynamics of the mixing between the cooling jets and main gas path, and high-quality three-component velocity data for CFD validation.
5. Test engine-representative, but generic, film-internal cooling configurations at a range of operating conditions.
Scope:
The data collected as part of this project will be at ambient conditions to avoid a complex and costly rig design. Utilising the established matched-Biot method will allow scaling of the results to real world values. The geometries used will also be generic to allow a database of measurements to be made available for academics and engine designers.
Resources and Planning:
The Turbomachinery Research Centre (TRC) will provide technician time as well as floor space within their laser cell. The build of the rig will be financed by Dr. Pountney's EPSRC First Grant. The current plan includes a first year of design, manufacture, and commissioning of the test rig, followed by two years of testing and six months of writing up. The PhD will be complete (including write-up) by March 2022.
The push for higher efficiencies in modern gas turbine engines has led to ever-increasing Turbine Entry Temperature (TETs). High pressure turbine blades now operate in an environment where the surrounding gas temperature exceeds the melting point of the materials from which the blades are made. To combat this, air from the compressor section of the engine is bled off and used to cool the blades. Two cooling techniques are employed to prevent damage to the blade from the high TETs: film cooling, where a thin film of coolant is introduced to the surface of the blade to reduce the driving-temperature for heat transfer; and internal cooling, where coolant is passed through a series of passages within the blade to convect heat from the internal surfaces.
Experimental research into turbine blade cooling has predominately treated film cooling and internal cooling as separate topics. This approach fails to capture conjugate heat transfer effects and the resulting impact on the component temperature distribution. The consequence of this is that blades are often conservatively overcooled at the expense of engine efficiency. Experimental data that couples the film and internal cooling would provide greater confidence in blade temperature predictions, reducing the need for superfluous use of coolant and lowering the risk of costly re-design of blades with inadequate cooling.
Aim:
The aim is to "fundamentally explore the heat transfer in film and internally cooled gas turbine blades through the use of novel, highly accurate experimental techniques". The objectives established to meet this aim are to:
1. Design and manufacture a modular test facility to model the heat transfer in a simplified portion of a cooled gas turbine blade.
2. Use IR thermography to obtain heat transfer coefficients from transient heat transfer experiments. This will provide important data for application of the matched-Biot technique.
3. Implement the matched-Biot technique to obtain non-dimensional surface temperature profiles from steady-state heat transfer experiments.
4. Use the CO2-PLIF and V3V technologies to provide detail on the fundamental fluid dynamics of the mixing between the cooling jets and main gas path, and high-quality three-component velocity data for CFD validation.
5. Test engine-representative, but generic, film-internal cooling configurations at a range of operating conditions.
Scope:
The data collected as part of this project will be at ambient conditions to avoid a complex and costly rig design. Utilising the established matched-Biot method will allow scaling of the results to real world values. The geometries used will also be generic to allow a database of measurements to be made available for academics and engine designers.
Resources and Planning:
The Turbomachinery Research Centre (TRC) will provide technician time as well as floor space within their laser cell. The build of the rig will be financed by Dr. Pountney's EPSRC First Grant. The current plan includes a first year of design, manufacture, and commissioning of the test rig, followed by two years of testing and six months of writing up. The PhD will be complete (including write-up) by March 2022.