Rotor Blade Root Stress Mitigation via Inclined Non-Contact Surfaces
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Solution Overview
Problem
High-speed rotation in turbomachines like gas and steam turbines leads to localized stress concentration in rotor blade attaching parts due to centrifugal force, limiting performance improvements.
Innovation Solution
The shape of the rotor blade root and disc blade groove is modified with protruding and recessed parts having inclined non-contact surfaces at a negative angle, shifting the load transmission path and reducing stress concentration without increasing dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotation speed of the rotating body is increased to improve turbomachine performance, then the power and efficiency are improved, but the stress due to centrifugal force increases and concentrates in the blade root attaching parts
Solution Approach 1:
The patent applies local quality by creating asymmetric stress distribution through inclined non-contact surfaces in the blade root and blade groove. The negative angle inclination (sloping toward the radially inside) is strategically placed only in specific non-contact regions, allowing stress to be redistributed away from high-stress contact areas while maintaining overall structural integrity. This localized geometric modification enables the blade root to withstand higher centrifugal forces without increasing overall dimensions.
2Length of moving object
If the height dimension of rotor blades is increased to improve performance, then the blade area and power generation are improved, but the stress in the blade root attaching parts increases
Solution Approach 1:
The patent changes the geometric parameters of the blade root and blade groove interfaces by introducing inclined non-contact surfaces with negative angles. This parameter modification alters the stress distribution pattern, allowing longer blades to be accommodated without proportionally increasing stress in the attaching parts. The inclined surfaces create a more favorable stress path that redistributes loads away from critical contact regions.
3Stress or pressure
If the dimensions of the blade root and blade groove are increased to reduce stress concentration, then the stress distribution is improved, but the overall device size increases
Solution Approach 1:
The patent applies inversion by sloping the non-contact surfaces toward the radially inside (negative angle) rather than the conventional radially outside direction. This reversed inclination creates compressive stress components that counteract tensile stresses in critical areas, effectively reducing stress concentration without requiring larger dimensions. The inverted geometry allows stress mitigation while maintaining compact blade root and blade groove sizes.
Data Source
AI summary
Provided is a rotor blade configured to be implanted in a disc of a rotating body, the rotor blade including a blade root, wherein in a cross-sectional shape of the blade root, the blade root includes at least one stage of protruding parts protruding toward opposite sides with respect to a direction containing a circumferential component, the protruding parts being configured to lock the blade root to the disc, each of the protruding parts has a contact surface configured to come into contact with the disc and inclined so as to extend toward a center part of the blade root from radially inside to radially outside, and each of the protruding parts has a non-contact surface configured not to come into contact with the disc and inclined so as to extend toward the center part of the blade root from the radially inside to the radially outside.