Turbine Rotor Blade Root Stress Distribution
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Solution Overview
Problem
The blade root portion of turbine rotor blades in gas turbines experiences stress concentration due to centrifugal and thermal loads, leading to reduced fatigue life, and increasing the thickness of teeth at the base to alleviate stress on one tooth results in increased stress on the rotor disc's blade groove, necessitating a solution that balances these stresses.
Innovation Solution
The turbine rotor blade design features teeth at different positions in the blade height direction with varying spacings between them, allowing for a greater distance between intersections on the base-side first tooth compared to other teeth, which increases its thickness while maintaining appropriate load distribution and reducing stress on the rotor disc's blade groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the base-side first tooth is increased to reduce stress on the tooth, then the strength of the tooth increases and stress on the tooth decreases, but the stress in the rotor disc blade groove increases
Solution Approach 1:
The patent applies local quality by making each tooth have different thickness characteristics tailored to its specific stress conditions. The base-side first tooth has greater thickness to handle higher stress, while other teeth have smaller thickness. This localized differentiation optimizes strength distribution without unnecessarily increasing stress on the rotor disc blade groove.
Solution Approach 2:
The patent employs asymmetry by designing unequal spacing between teeth and unequal thickness for each tooth. The spacing between adjacent teeth varies, with the base-side first tooth having different spacing characteristics compared to other teeth. This asymmetric design allows optimal stress distribution across the blade root portion while preventing excessive stress concentration on the rotor disc blade groove.
2Stress or pressure
If the spacing between base-side teeth is increased to reduce stress concentration, then stress distribution improves, but the structural compactness decreases
Solution Approach 1:
The patent applies local quality by varying the spacing between teeth based on their specific positions and stress conditions. The base-side first tooth has different spacing compared to other teeth, optimized for its higher stress environment. This localized spacing adjustment improves stress distribution while maintaining overall structural compactness.
Solution Approach 2:
The patent employs parameter changes by varying both the spacing parameters and thickness parameters of different teeth. The spacing between base-side teeth is optimized to reduce stress concentration, while the thickness of each tooth is adjusted according to its specific stress requirements. These parameter optimizations achieve improved stress distribution without excessive loss of structural compactness.
Data Source
AI summary
One of spacing between the base-side first tooth and the base-side second tooth or spacing between the base-side second tooth and the base-side third tooth is greater than spacing between the tip-side first tooth and the tip-side second tooth. When, in a cross-section perpendicular to an extension direction of a plurality of teeth, a straight line that connects tooth bottom portions formed between each adjacent teeth in the blade height direction is a first line, an intersection between the first line and a second line that includes a linear portion of a tip-side tooth surface of each of the plurality of teeth is a first intersection, and an intersection between the first line and a third line that includes a linear portion of a base-side tooth surface of each of the plurality of teeth is a second intersection, a distance between the first intersection and the second intersection in the base-side first tooth is greater than a distance between the first intersection and the second intersection in each tooth other than the base-side first tooth.