Cooled Rotor Blade Plenum Cooling Rear Overhang
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The rear overhang region of high-pressure turbine blades in gas turbine engines is difficult to cool effectively due to high heat transfer coefficients and secondary flows, leading to potential TBC shedding, overheating, and blade failure, as conventional cooling methods are inefficient and costly.
Innovation Solution
An annular flow path turbine rotor blade design featuring an internal elongate plenum chamber aligned with the circumferential direction to supply cooling air to exit holes on the rear overhang portion, optimizing film cooling and reducing aerodynamic mixing losses, with the option of non-circular cross-sections to manage stress and longer overhangs for improved sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cooling methods are used on the rear overhang region, then the structure is simple, but cooling effectiveness is insufficient leading to TBC shedding and blade failure
Solution Approach 1:
The cooling system is segmented into multiple functional zones: a plenum chamber for air distribution, multiple feed passages for different cooling zones, and numerous cooling holes strategically positioned on the platform and rear overhang region. This segmentation allows each zone to be optimized independently for cooling effectiveness while maintaining overall system reliability
Solution Approach 2:
Different cooling strategies are applied to different regions: the platform receives cooling through feed passages with specific hole patterns, while the rear overhang region receives dedicated cooling through separate feed passages and cooling holes positioned to address its unique thermal environment. This local quality approach ensures each region receives appropriate cooling without oversimplifying the overall system
2Temperature
If cooling air is extracted from the turbine, then turbine components are cooled, but engine operating efficiency decreases
Solution Approach 1:
Cooling air is introduced into the blade structure at the root portion before the hot gas flow reaches the critical regions. The air travels through internal feed passages and cooling holes to reach the platform and rear overhang region in advance, establishing a protective cooling film before thermal damage can occur. This preliminary action maximizes the cooling effectiveness of the extracted air
Solution Approach 2:
The internal feed passages and cooling holes act as intermediaries, transporting cooling air from the compressor through the blade structure to the regions requiring cooling. This intermediary system allows cooling air to be delivered precisely where needed, maximizing its effectiveness and reducing the total amount of air required for cooling
3Reliability
If the rear overhang region is not adequately cooled, then the cooling system is simple, but TBC shedding and thermal fatigue cracking occur
Solution Approach 1:
The cooling system is segmented into multiple functional zones: a plenum chamber for air distribution, multiple feed passages for different cooling zones, and numerous cooling holes strategically positioned on the platform and rear overhang region. This segmentation allows each zone to be optimized independently for cooling effectiveness while maintaining overall system reliability
Solution Approach 2:
Different cooling strategies are applied to different regions: the platform receives cooling through feed passages with specific hole patterns, while the rear overhang region receives dedicated cooling through separate feed passages and cooling holes positioned to address its unique thermal environment. This local quality approach ensures each region receives appropriate cooling without oversimplifying the overall system
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances convective cooling effectiveness, allows for longer overhangs, improves gas path sealing, and extends the life of thermal barrier coatings and reduces thermal fatigue cracking by ensuring adequate cooling of the rear overhang region.
Implementation Method 1
the plenum chamber supplying the cooling air to a plurality of exit holes formed in the external surface of the rear overhang portion to cool that portion
Implementation Method 2
The cooling air cools the NGV and rotor blade internally by convection and then exits the NGV and rotor blade through many small exterior holes 3 to form cooling films over the external aerofoil surfaces
Implementation Method 3
The NGV and rotor blade may be further protected from the hot gas temperatures by thermal barrier coatings (TBCs) formed on these components
Data Source
AI summary
A cooled turbine rotor blade for a gas turbine engine is provided. The engine has an annular flow path for conducting working fluid though the engine. The blade has an aerofoil section for extending across the annular flow path. The blade further has a root portion radially inward of the aerofoil section for joining the blade to a rotor disc of the engine. The blade further has a platform between the aerofoil section and the root portion. The platform extends laterally relative to the radial direction of the engine to form an inner boundary of the annular flow path and to provide a rear overhang portion which projects in use towards a corresponding platform of a downstream nozzle guide vane. The platform contains at least one internal elongate plenum chamber for receiving cooling air. The longitudinal axis of the plenum chamber is substantially aligned with the circumferential direction of the engine. The plenum chamber supplies the cooling air to a plurality of exit holes formed in the external surface of the rear overhang portion to cool that portion.