Gas Turbine Rotor Heat Shield Cooling Flow Control
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Solution Overview
Problem
The efficiency of gas turbine engines is limited by the difficulty in achieving effective sealing and cooling of turbine rotor discs and drive arms due to high temperature gradients and complex geometry, leading to increased leakage and reduced cooling performance.
Innovation Solution
A heat shield with a connecting flange and knife edge members forms a labyrinth seal, directing cooling air through recessions in connecting flanges and controlling flow with slots and orifices to prevent hot gas ingestion, ensuring efficient cooling and sealing by maintaining a larger rim gap area relative to flow restrictors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat shield arrangements are used to shield rotor discs and rotor structure from high temperature combustion products, then the structural elements can withstand higher temperatures, but the quantity of cooling air required increases, reducing engine efficiency
Solution Approach 1:
The heat shield is divided into multiple segments including a disc portion and blade platform portions that can independently rotate with the rotor. This segmentation allows the cooling air to be distributed more effectively across different thermal zones, reducing the total quantity of cooling air needed while maintaining adequate protection of all structural elements
Solution Approach 2:
The heat shield is designed to rotate dynamically with the rotor disc rather than being stationary. This dynamic configuration allows the heat shield to maintain optimal positioning relative to the combustion products and cooling air flow, improving cooling efficiency and reducing the amount of cooling air required to achieve adequate temperature protection
2Reliability
If classical heat shield arrangements are used, then cooling air can be directed to structural elements, but effective sealing of the cooling passage between heat shield and disc is difficult to achieve due to complex geometry and temperature gradients
Solution Approach 1:
The heat shield acts as a flexible-like structure that rotates with the rotor, maintaining continuous contact with the disc surface through centrifugal force and elastic deformation. This eliminates the need for complex mechanical sealing arrangements while ensuring effective sealing of the cooling passage between the heat shield and disc, preventing hot gas leakage
Solution Approach 2:
The rotating heat shield utilizes the rotor's own rotation to maintain sealing contact with the disc. The centrifugal force generated during rotation automatically presses the heat shield against the disc surface, creating an effective seal without requiring additional sealing mechanisms or components
3Temperature
If cooling air is extracted from the compressor to cool turbine elements, then the structural elements can withstand higher temperatures, but engine performance is reduced due to the cooling air off-take
Solution Approach 1:
The heat shield is designed to provide localized cooling protection only where and when it is most needed - at the disc and blade platform regions exposed to combustion products. This targeted approach allows cooling air to be used more efficiently, reducing the total quantity required compared to blanket cooling of all turbine elements, thereby minimizing the impact on engine performance
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
This configuration effectively protects rotor discs and drive arms from hot gases, maintains efficient cooling flow, and prevents hot gas ingestion, enhancing engine performance by optimizing cooling air usage and minimizing leakage.
Implementation Method 1
The heat shield extends rearward from the flange region to surround the shape of the disc and the disc drive arm but leaving a predetermined annular space between the heat shield and the disc or disc drive arm which defines the heat shield cooling flow passage
Implementation Method 2
A heat shield includes a connecting flange in its front section attached to adjacent disc flanges and has at least one knife edge member to form a labyrinth seal with the stator seal land
Data Source
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AI summary
Gas turbine rotor in which flow from the turbine internal cavity is directed through slots (45) in the connecting flanges (52-53) of adjacent rotor rows to a cooling flow passage (43) of a heat shield (60) controlled by flow restrictors (82). A portion of such flow is directed to bucket grooves (34) beneath the blade attachments (25B), thereby cooling the disc rim (32), and controlled by flow restrictors (80). The remaining flow is exhausted through a heat shield rim gap (81) thereby cooling the front disc rim (32) and the blade shank cavity (25A).