Lobed Turbine Blade Root Sealing
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Solution Overview
Problem
Turbine blades in gas turbine engines face challenges in reliable retention and cooling air sealing due to high speeds and temperatures, leading to excessive leakage of cooling air.
Innovation Solution
The design incorporates a turbine blade with lobed edges and tabs that extend laterally from the root, conforming to the shape of the edges, which are received in fir-tree-shaped slots on the disc, and a cover plate to seal gaps and direct air passages, ensuring fluid connection and reduced air leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turbine blades are retained on the turbine disc using conventional methods, then the blades can be mounted on the disc, but excessive leakage of cooling air occurs and retention reliability is compromised at high speeds
Solution Approach 1:
The root of the turbine blade is divided into multiple lobed edges that fit into corresponding lobed slots on the turbine disc, creating multiple separate sealing surfaces instead of a single continuous interface. This segmentation allows each lobe to independently seal against air leakage while maintaining structural integrity at high rotational speeds
Solution Approach 2:
Tabs are added extending laterally outward from the lobed edges of the root in the circumferential direction, creating a third dimensional sealing barrier beyond the radial and axial dimensions. These tabs seal against the circumferential face of the disc, blocking leakage paths that conventional radial sealing cannot prevent
2Temperature
If cooling air is directed into cooling inlets formed in the blades, then the blades can be cooled at high temperatures, but excessive leakage of cooling air occurs reducing cooling efficiency
Solution Approach 1:
The sealing structure is segmented into multiple lobed edges and corresponding lobed slots, creating multiple discrete sealing zones around the circumference of the blade root. This segmentation ensures that cooling air introduced into the blade's internal cooling passages is contained within each sealing zone, preventing leakage and maximizing cooling efficiency
Solution Approach 2:
The lobed edges and tabs act as intermediary sealing elements between the cooling air supply system and the blade root interface. These intermediaries create a barrier that directs cooling air into the intended cooling passages while preventing it from leaking into the gap between the blade and disc
Data Source
AI summary
The turbine blade includes an airfoil, a root connected to the airfoil and having lobed edges spaced apart on laterally opposed sides of an axis extending axially through the root, and an air passage extending through the airfoil and the root. A first tab extends at least partially along and laterally outward from a first edge of the laterally opposed lobed edges, and a second tab extending at least partially along and laterally outward from a second edge of the laterally opposed lobed edges.