Turbine Blade Root Heat Shield Interlock and Cooling
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Solution Overview
Problem
Existing thermal shielding solutions for gas turbine bucket grooves and disc rims face challenges such as complex assembly, coolant air leakage, and manufacturing difficulties, which impact the mechanical strength and lifespan of turbine blades and discs due to thermal gradients and stress ranges.
Innovation Solution
An assembly featuring a blade with a root portion and heat shield that interlocks with the bucket groove, incorporating a cooling air inlet duct and channels within the blade body, and a heat shield that extends to cover gaps and guide cooling air effectively, preventing leakage and enhancing thermal shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate component heat shield is inserted between the root portion and the radially inner wall of the bucket groove, then thermal shielding effectiveness is improved, but assembly complexity and time increase
Solution Approach 1:
The heat shield is integrally formed with the root portion as a single monoblock component, eliminating the need for separate assembly operations. The integral construction merges the heat shield function directly into the blade root structure, resolving the contradiction by achieving thermal shielding effectiveness without increasing assembly complexity.
2Manufacturing precision
If an integral heat shield is provided at the blade root, then manufacturing precision is improved, but manufacturing complexity increases due to obstacles for finishing operations
Solution Approach 1:
The monoblock root portion is designed with integrated cooling channels that are accessible from the external surface, allowing finishing operations to be performed on the outer surfaces while the internal cooling channel geometries are manufactured separately through casting or additive processes. This segmentation of manufacturing approaches resolves the contradiction by achieving precise heat shield positioning without obstructing finishing operations.
3Temperature
If cooling air is delivered adjacent to the rim of the turbine disc, then cooling effectiveness is improved, but thermal gradients in the disc increase leading to higher stress range
Solution Approach 1:
The heat shield is positioned specifically at the radially inner surface of the bucket groove to provide localized thermal protection where the cooling air flow contacts the disc. This local shielding prevents excessive cooling of the disc rim area, maintaining thermal gradients within acceptable limits while still achieving effective cooling where needed, thus resolving the contradiction between cooling effectiveness and stress range.
4Reliability
If the heat shield extends to cover gaps at the front face of the disc, then thermal shielding is enhanced, but the risk of coolant air leakage increases
Solution Approach 1:
The heat shield incorporates a sealing lip or barrier edge that extends to contact the front face of the disc, creating an intermediary seal between the cooling air flow and the external environment. This sealing feature prevents coolant air leakage while maintaining enhanced thermal shielding coverage, resolving the contradiction by introducing a mediating sealing structure.
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 coolant air leakage and enhances thermal shielding, improving the mechanical strength and lifespan of turbine blades and discs by optimizing heat transfer and stress management.
Implementation Method 1
The adjutting portion is configured to block leakage of coolant air into the bucket groove and to guide cooling air into a cooling duct
Implementation Method 2
heat shield configured to be received between an end of the root portion and a radially inner surface of the bucket groove... to provide thermal shielding
Implementation Method 3
cooling channels extending from the duct through the blade body... Heat transfers between this cooling air flow and the turbine disc
Implementation Method 4
the heat shield and the root portion are interconnected to one another such that separation between the heat shield and the root portion in a radial direction is deterred
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An assembly for receiving in a radially extending bucket groove (31) of a turbine disc (22), the assembly comprising; a turbine blade having an elongate body (26) of aerofoil cross-section, a root portion (24) at one end of the elongate body (26) and a tip at the other, the root portion (24) configured to be retained in the bucket groove (31); and a heat shield (27) configured to be received between an end of the root portion (24) and a radially inner surface of the bucket groove (31) and to interlock with the root portion (24) in a manner which deters separation in a radial direction.