Endwall Cooling System Differential Thermal Expansion
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Solution Overview
Problem
Components within a gas turbine engine's turbine flow path experience thermal stress and cooling inefficiencies due to differences in thermal expansion between the endwall and impingement plate, leading to potential braze failure and inadequate cooling.
Innovation Solution
An air distribution system comprising a wall and a plate with a passage between them, where the plate is fixedly coupled to a protrusion, and includes outlets and ribs to direct airflow efficiently, reducing thermal stress and enhancing heat transfer by breaking up laminar flow and increasing turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an impingement plate is brazed to the endwall to create a cooling passageway, then cooling effectiveness is improved, but differences in thermal expansion cause the braze to fail
Solution Approach 1:
The cooling system is divided into separate functional components: the endwall with cooling passages and the impingement plate with impingement holes. These segments are connected through a flexible sealing arrangement rather than a rigid braze joint, allowing each segment to expand independently while maintaining the cooling function.
Solution Approach 2:
A flexible seal (such as a bellows or corrugated diaphragm) is introduced between the endwall and impingement plate to accommodate differential thermal expansion. This flexible film maintains the sealing of the cooling passageway while allowing relative movement between the two components during thermal cycles.
2Use of energy by moving object
If air flows laminarly through the cooling passage, then flow resistance is reduced, but heat transfer efficiency decreases
Solution Approach 1:
The impingement plate directs cooling air through holes to create turbulent impingement flow against the endwall surface. This mechanical disruption of the boundary layer enhances convective heat transfer by preventing thermal boundary layer formation, converting what would be laminar flow into effective turbulent cooling.
Solution Approach 2:
The system uses controlled air flow dynamics where cooling air is pressurized and directed through the impingement plate holes to create high-velocity jets. This pneumatic approach transforms the cooling mechanism from passive laminar flow to active turbulent impingement, significantly improving heat transfer coefficients.
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 system provides effective cooling to the endwall, reducing the risk of cracking or fracturing due to thermal expansion differences and improving heat transfer efficiency, thereby maintaining the integrity and performance of the turbine section.
Implementation Method 1
breaking up laminar flow of the air within the cooling passage and aiding heat transfer from the endwall to the air
Implementation Method 2
differences in thermal expansion between the endwall and the impingement plate
Data Source
AI summary
An air distribution system for cooling a component in a heated gas environment may be provided, where the air distribution system includes a wall and a plate. The wall includes an inner surface, an outer surface configured to be exposed to the heated gas environment, and a protrusion extending from the inner surface of the wall. The plate is fixedly coupled to the protrusion and is space apart from the inner surface of the wall. The plate includes an outer edge. A passage is defined between the plate and the inner surface of the wall. The inlet of the passage is defined by the outer edge of the plate.