Gas Turbine Exit Flow Discourager for Cavity Cooling
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Solution Overview
Problem
In gas turbine engines, hot air flow can bleed into air cavities within the turbine, elevating temperatures and reducing the longevity of components.
Innovation Solution
The introduction of an exit flow discourager, featuring annular teeth and recirculation regions on the turbine diaphragm and disk, increases the pressure of cooling air and creates a tortuous path to prevent the ingestion of hot combustion gases into cavities, thereby reducing temperature and extending component lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If hot air flow is allowed to pass through the turbine cavity, then the cooling air pressure is maintained, but the temperature of cavity components increases and component longevity decreases
Solution Approach 1:
The exit flow discourager is segmented into multiple teeth (first tooth, second tooth, etc.) arranged around the cavity perimeter. Each tooth creates individual flow disruption zones, collectively forming a comprehensive barrier that prevents hot air ingress while maintaining cooling air pressure through the segmented structure.
Solution Approach 2:
The teeth of the exit flow discourager act as intermediary elements between the cooling air flow and the hot combustion gases. These teeth create recirculation regions that mediate the interaction between cool and hot flows, preventing direct contact while maintaining the pressure differential.
2Temperature
If cooling air flow is increased to reduce cavity temperature, then component longevity improves, but the complexity of the turbine structure increases
Solution Approach 1:
The teeth of the exit flow discourager serve multiple functions simultaneously: they act as flow barriers to prevent hot air ingress, create recirculation regions to enhance cooling air effectiveness, and maintain structural integrity of the diaphragm. This multi-functionality reduces the need for additional separate cooling components.
Solution Approach 2:
The exit flow discourager utilizes the existing cooling air flow dynamics to create recirculation regions that enhance cooling effectiveness. The structure self-adjusts to the flow conditions, using the cooling air pressure differential to maintain the barrier function without requiring additional active control mechanisms.
3Reliability
If teeth are added to the diaphragm to prevent hot gas ingestion, then component longevity improves, but the manufacturing complexity increases
Solution Approach 1:
The teeth are strategically positioned at specific locations around the diaphragm perimeter where hot air ingress is most likely to occur. The local quality of the teeth (depth, width, spacing) is optimized for each position to effectively prevent hot gas ingestion while minimizing manufacturing complexity. The teeth extend only the necessary distance to achieve flow disruption without requiring excessive material removal or addition.
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 the temperature within cavities and prolongs the service life of gas turbine engine components by enhancing the pressure of cooling air and preventing hot gas ingestion.
Implementation Method 1
The teeth may increase the pressure of the cooling air flowing through certain cavities
Implementation Method 2
The exit flow discourager includes an annular first tooth axially extending a first length from the axial facing surface of the turbine diaphragm towards the annular flat surface of the turbine disk
Data Source
AI summary
A turbine stage for a gas turbine engine is disclosed. The turbine stage includes a turbine disk and a turbine diaphragm, forming a cavity there between. The turbine stage also includes an exit flow discourager comprised of at least two teeth. The teeth may be located radially apart from each other, each tooth including a length extending in the axial direction and a width extending in the radial direction. A channel is formed between the teeth and an axially adjacent surface. A recirculation region may be formed in between each pair of teeth.