Turbomachinery Blade Platform Relief Hole and Cooling Design
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Solution Overview
Problem
Gas turbine rotor blades experience premature cracking at the root trailing edge and platform region due to thermal mechanical fatigue and stress, leading to early retirement, with existing undercut solutions failing to balance stress reduction without creating new stress areas.
Innovation Solution
A turbomachinery blade design featuring a blind relief hole in the platform near the trailing edge and a trailing edge cutback, along with a plurality of cooling holes in the platform, to reduce stress and prevent cracking, while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If material is removed from the trailing edge to eliminate cracking, then structural integrity is restored, but blade strength is reduced leading to new cracking
Solution Approach 1:
The patent applies local quality by creating an undercut only in the specific region where cracking occurs (the trailing edge root area), while maintaining the original blade geometry elsewhere. This localized material removal addresses the cracking problem without compromising the overall structural integrity and strength of the blade.
Solution Approach 2:
The patent changes the geometric parameters of the trailing edge by introducing an undercut with specific depth and angle parameters. This parameter modification allows sufficient material removal to eliminate cracks while controlling the dimensions to maintain adequate blade strength and prevent new cracking formation.
2Stress or pressure
If an undercut is machined into the blade platform to reduce stress, then stress level is reduced, but new stress areas are created in the grooved region
Solution Approach 1:
The patent applies curvature principles by using rounded fillets and smooth transitions in the undercut geometry, avoiding sharp corners that would create stress concentrations. The grooved region is designed with curved surfaces that distribute stress more evenly, preventing new stress areas while maintaining the stress reduction benefit.
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 proposed design significantly reduces maximum principal stress at the root trailing edge and increases thermal mechanical fatigue life, with the blind relief hole reducing stress by 17% and the cooling holes enhancing cooling flow, resulting in a 150% increase in TMF life and minimizing new cracking risks.
Implementation Method 1
a plurality of cooling holes disposed in the platform... the cooling holes enhancing cooling flow
Implementation Method 2
forming a blind relief hole in the platform proximate the trailing edge of the airfoil... the blind relief hole reducing stress by 17%
Data Source
AI summary
A method is disclosed that includes providing a turbomachinery blade having an airfoil connected to a platform in a root region of the turbomachinery blade. The airfoil has a trailing edge extending from the root region to a tip distal from the root region. The method further includes forming a blind relief hole in the platform proximate the trailing edge of the airfoil, and forming a plurality of cooling holes in the platform.