Gas Turbine Rotor Blade Cooling Cavity Design
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Solution Overview
Problem
The connection zone between the trailing edge and the platform of gas turbine rotor blades experiences high thermal stresses due to its remote location from cooling air, leading to potential cracking issues.
Innovation Solution
A cavity is formed in the stiffener adjacent to the platform, aligned with the trailing edge, connected to a cooling fluid feed duct and outlet orifices, which reduces the temperature gradient and risk of cracking by cooling the material between the trailing edge and the platform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the connection zone between trailing edge and platform is left without additional cooling, then the structure remains simple, but the zone is subjected to intense thermal stresses leading to crack formation
Solution Approach 1:
The invention applies local cooling specifically to the connection zone between the trailing edge and platform by forming cooling orifices in the platform at the location where thermal stresses are highest. This targeted approach provides enhanced cooling exactly where needed without requiring a complete redesign of the entire cooling system, thus improving reliability while maintaining reasonable complexity.
Solution Approach 2:
The cooling system is segmented into existing cooling ducts that deliver cooling air to the platform, and additional localized cooling orifices formed directly in the platform at the connection zone. This segmentation allows the existing cooling infrastructure to be supplemented with targeted local cooling without requiring a completely new system, resolving the contradiction between reliability improvement and complexity increase.
2Temperature
If cooling orifices are formed in the platform to cool the connection zone, then thermal stresses are reduced, but the platform structure becomes more complex
Solution Approach 1:
The invention changes the thermal parameters of the connection zone by introducing cooling orifices in the platform that allow cooling air to flow directly through the connection zone. This parameter change (adding cooling capability) reduces temperature gradients and thermal stresses without fundamentally altering the platform's structural function, thus achieving temperature uniformity with minimal increase in structural complexity.
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
The solution effectively reduces thermal stresses and the risk of cracking by minimizing the temperature gradient between the connection zone and the stiffener, ensuring the structural integrity of the rotor blades.
Implementation Method 1
Cooling fluid flowing in the cavity of the stiffener can thus exit without disturbing the flow of gas leaving the blade
Implementation Method 2
This leads to a significant reduction in the temperature gradient between said connection and the stiffener
Implementation Method 3
The cooling air escapes in particular via exhaust slots opening out downstream along the trailing edge
Data Source
AI summary
A rotor blade for a gas turbine, in particular a turbojet, the blade comprising an airfoil, a platform connecting the airfoil to a blade root and having at least one stiffener extending under the downstream portion of the platform, together with means for cooling the blade by a flow of cooling fluid in ducts formed in the blade and in a cavity formed in the stiffener substantially in register with the trailing edge of the blade, and including outlet orifices facing downstream.