Airfoil Insert Seal Design for Gas Turbine Cooling Leakage
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Solution Overview
Problem
In gas turbine engines, airfoil inserts used for convective cooling often experience coolant leakage back into the cavity due to relative movement between the insert and the flow-directing element, reducing the heat transfer coefficient and cooling effectiveness.
Innovation Solution
An airfoil insert with a tubular body and affixed plates at the outlet, featuring tabs that extend perpendicularly and interact with discouragers on the flow-directing element's shelf to direct coolant to an exit port while restricting leakage, enhancing the seal and reducing coolant flow back into the cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the airfoil insert is affixed at only one end to accommodate thermal expansion differences, then the insert can accommodate relative movement without damage, but a gap opens at the free end allowing coolant leakage that reduces cooling effectiveness
Solution Approach 1:
The patent applies local quality by creating a seal structure specifically at the free end of the insert where the gap forms. The seal member is positioned only at the outlet end rather than along the entire insert length, addressing the leakage problem locally without constraining the thermal expansion movement elsewhere. This localized sealing approach maintains the durability benefit of single-end attachment while eliminating coolant leakage at the critical gap location.
Solution Approach 2:
The patent introduces a seal member as an intermediary element between the insert and the cavity wall. This seal member fills the gap that naturally forms due to thermal expansion, preventing coolant from leaking back into the cavity. The intermediary seal member resolves the contradiction by allowing the insert to move freely for thermal expansion accommodation while simultaneously blocking the leakage path at the gap location.
2Temperature
If coolant is allowed to flow freely through the insert, then cooling effectiveness is maximized through high velocity impingement jets, but coolant leaks back into the cavity between the insert and flow-directing element reducing heat transfer coefficient
Solution Approach 1:
The seal member is positioned locally at the outlet end of the insert where the gap forms, rather than along the entire length. This localized sealing maintains high velocity coolant flow and impingement cooling effectiveness in the main flow path while preventing leakage only at the specific location where the gap exists, thus preserving the heat transfer coefficient without restricting overall coolant flow.
Solution Approach 2:
The patent converts the potentially harmful coolant leakage into a controlled flow path. By positioning the seal member to block the gap, the coolant that would have leaked is redirected to maintain impingement cooling effectiveness. The seal member transforms the harmful leakage effect into a beneficial concentrated cooling flow against the cavity wall.
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 minimizes coolant leakage and enhances heat transfer by directing coolant inward toward the exit port, improving the cooling efficiency of the flow-directing elements.
Implementation Method 1
A convective cooling system utilizes coolant, such as pressurized air from a forward compressor section of the gas turbine engine, to remove heat from the flow-directing elements. The coolant circulates through internal cavities and passages, removing heat via convection, before exiting.
Implementation Method 2
The coolant discharges from the perforations in high velocity jets, spraying across the gap between the insert and cavity wall. By impinging against the cavity wall, the heat transfer coefficient increases, thus enhancing the cooling effectiveness.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Disclosed are examples of flow-directing elements, airfoil inserts, and assemblies thereof. A flow-directing element (12) has an inner buttress (14) with an airfoil (18) extending outwardly therefrom. The airfoil includes a cavity (34) that extends within the airfoil to an exit port (66) disposed in the inner buttress. A shelf (76) disposed about the buttress defines the exit port, and the shelf includes a discourager (78a) extending into the cavity. An airfoil insert (36) has a tubular body (38) with an outlet (54) at one end. A plate (58, 60) affixed to the body at the outlet partially blocks the outlet, and includes a tab (64) extending away from the body and defining a portion of an outlet periphery. Upon assembly of the flow directing element and the insert, the tab interacts with the discourager to direct a coolant to the exit port while restricting leakage of the coolant back into the cavity, between the airfoil insert and the flow-directing element.