Turbine Blade Outer Platform Locking for Vibration Damping
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Solution Overview
Problem
Turbomachine blades made of ceramic matrix composite materials are prone to low mechanical stresses and expansion differences, leading to increased vibratory stresses and reduced contact forces due to non-expansion, necessitating improved damping solutions.
Innovation Solution
The blades incorporate locking means on the radially outer platform, comprising obliquely inclined locking walls that receive a locking plate, forming a dovetail mechanical assembly to dampen vibratory stresses and maintain blade position without disrupting operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If blades are made of ceramic matrix composite materials to resist high temperatures and reduce weight, then temperature resistance is improved and weight is reduced, but mechanical strength decreases and contact force reduces due to low thermal expansion
Solution Approach 1:
The patent employs ceramic matrix composite materials for the blades, which provide superior temperature resistance and weight reduction compared to traditional metal alloys. The composite structure allows the blades to maintain integrity at high temperatures while managing the reduced mechanical strength through careful design of the locking mechanism.
Solution Approach 2:
The patent addresses the low thermal expansion characteristic of ceramic matrix composite materials by designing a locking mechanism that compensates for reduced contact force. The mechanical locking structure ensures adequate contact pressure between adjacent blades despite the materials' low expansion properties during thermal cycling.
2Object-affected harmful factors
If contact between circumferentially adjacent blades is introduced to dampen vibrations, then vibration damping is improved, but mechanical stresses on ceramic matrix composite blades increase
Solution Approach 1:
The patent extracts the vibration damping function from the blade material itself and implements it through a separate mechanical locking mechanism. This allows vibration damping to be achieved through controlled contact between adjacent blades without requiring the blade material to withstand high contact stresses, thereby protecting the fragile ceramic matrix composite structure.
Solution Approach 2:
The locking mechanism acts as an intermediary between adjacent blades, providing the necessary contact for vibration damping while distributing and reducing the mechanical stresses transmitted to the blade structures. The mechanism mediates the interaction between blades to achieve damping with minimal stress imposition.
3Object-affected harmful factors
If locking means are added to the radially outer platform to limit vibratory stresses, then vibration damping is improved, but device complexity increases
Solution Approach 1:
The locking mechanism is segmented into discrete locking walls and locking elements that can be integrated into the existing blade structure. Each locking wall is configured with specific geometric features that engage with corresponding features on adjacent blades, creating a modular system that limits vibratory stresses without requiring a complete redesign of the blade architecture.
Solution Approach 2:
The locking mechanism utilizes the circumferential dimension by extending locking walls from the radially outer platform to engage with adjacent blades. This dimensional approach allows vibration damping to be achieved through circumferential locking features rather than requiring complex radial or axial modifications to the blade 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 limits vibratory stresses and maintains blade position, reducing mechanical stresses and expansion effects, while using simple mechanical means that do not alter the blade's functional operation.
Implementation Method 1
The vibrations of the blade during operation induce relative slip at this contact, which, combined with the contact pressures, creates vibration damping by friction.
Implementation Method 2
two locking walls for locking the radially outer platform each configured to receive a circumferential end of a locking plate
Data Source
AI summary
A blade intended to be mounted on a turbomachine rotor with an axis, the blade including a root configured to be mounted in a groove that opens to the outer periphery of a disk of the turbomachine rotor; an airfoil extending the root, in a radial direction with respect to the axis, and having an aerodynamic profile; a radially inner platform separating the airfoil from the root; a heel which extends as a continuation of the airfoil at a free radial end of the blade, at the end of the airfoil radially opposite the root, the heel including a radially outer platform, wherein the heel includes means for locking the radially outer platform with respect to another circumferentially adjacent radially outer platform.