Trapped Spring Balance Weight for Turbine Rotor Balancing
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Solution Overview
Problem
Smaller gas turbine rotors face challenges in balancing due to the absence of bolt holes, which limits the use of separable balance weights, often requiring irreversible material removal that risks damaging safety-critical components like integrally-bladed rotors.
Innovation Solution
A trapped spring balance weight design featuring a block-like centerbody with resilient spring arms and a limit tab, allowing for repositioning without permanent deformation, is used to redistribute mass and balance the rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separable balance weights are used with bolt holes, then balance weights can be re-positioned to redistribute mass, but the rotor structure becomes more complex and heavier
Solution Approach 1:
The balance weight is divided into two functional parts: a removable weight element and a retained feature (depression or protrusion) on the rotor. This allows the balance weight to be repositioned by simply removing and reattaching the small weight element, rather than requiring complex adjustable mechanisms. The segmentation enables easy repositioning while keeping the overall rotor structure simple.
2Manufacturing precision
If material is removed for balancing, then mass redistribution is achieved, but the rotor component is permanently damaged and at risk
Solution Approach 1:
Instead of permanently removing material from the critical rotor component, the invention creates a separate, sacrificial balance weight element that can be removed and repositioned. The balance correction is achieved by adding or moving this separate weight element, leaving the main rotor component intact and undamaged. This recovers the rotor's full structural integrity while achieving the required balancing precision.
3Weight of moving object
If tie bolts are used to reduce weight, then rotor weight is reduced, but convenient features for attaching balance weights are eliminated
Solution Approach 1:
The balance weight feature (depression or protrusion) is integrated into the existing rotor structure in a space-efficient manner. The feature nests within or alongside existing rotor components, requiring minimal additional material and maintaining the lightweight tie bolt construction. This nested integration provides the necessary attachment capability for balance weights without adding significant weight or complexity to the rotor.
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
This design enhances process control, reduces stress concentrations, maintains engine cleanliness, and shortens the balancing cycle by enabling easy repositioning of balance weights without material removal, thus avoiding damage to critical components.
Implementation Method 1
a block-like centerbody; a pair of resilient spring arms extending laterally from opposite sides of the centerbody
Implementation Method 2
the spring arms and the centerbody resiliently bear against the flange and the hub surface, respectively, so as to retain the balance weight in the pocket
Data Source
AI summary
A balance weight for a turbine rotor includes: a block-like centerbody; a pair of resilient spring arms extending laterally from opposite sides of the centerbody, the centerbody and the spring arms collectively defining an arcuate shape; at least one locating structure extending from a radially outer surface of the balance weight; and a limit tab extending radially inward from a distal end of each of the spring arms.