Turbine Blade Coupling Element for Vibration Damping
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Solution Overview
Problem
Existing turbine stages face challenges in reducing vibration-induced stress on blades due to the need for specialized blade designs and material thickness to accommodate coupling elements, which limits retrofitting and increases the risk of notch stresses and material weakening.
Innovation Solution
A coupling element with a coupling sleeve and pin, featuring internal and external threads, is used to mechanically couple turbine blades without requiring special blade designs or minimum thickness, allowing for easy retrofitting and eliminating notch stresses by using through holes with identical diameters and a form-fit mechanism to prevent loosening during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coupling elements are integrated into turbine blades with internal threads and closure elements, then vibration damping is achieved, but notch stresses and material weakening occur
Solution Approach 1:
The coupling element is divided into two separate components: a coupling sleeve that fits into the through-hole and a separate coupling nut that threads onto the sleeve. This segmentation eliminates the need for internal threads in the blade itself, avoiding notch stresses while maintaining the vibration damping function through the friction between the coupling components.
Solution Approach 2:
The coupling sleeve acts as an intermediary component between the blade's through-hole and the coupling nut. Instead of threading directly into the blade material (which causes stress concentration), the sleeve provides a smooth bore that receives the nut, eliminating direct notch stresses in the blade while still enabling the coupling mechanism to damp vibrations.
2Reliability
If turbine blades are designed with special geometry to accommodate coupling elements, then vibration reduction is achieved, but retrofitting existing turbines becomes difficult
Solution Approach 1:
The coupling element system uses a standardized coupling sleeve and nut assembly that can be installed in any turbine blade with a simple through-hole. This universal design does not require blade-specific geometry modifications, allowing the same coupling mechanism to be retrofitted across different turbine models and configurations, thereby achieving both vibration reduction and adaptability.
Solution Approach 2:
Instead of modifying the blade geometry to accommodate the coupling element (traditional approach), the invention inverts the approach by having the coupling element adapt to a simple through-hole in the blade. The coupling sleeve and nut assembly is designed to fit into the existing blade structure without requiring the blade to be specially shaped, enabling easy retrofitting.
3Reliability
If coupling elements require minimum blade thickness, then proper coupling is achieved, but existing blades cannot be used without modification
Solution Approach 1:
By segmenting the coupling mechanism into a sleeve and separate nut components, the design eliminates the need for the blade material itself to provide threading. The through-hole can be any reasonable diameter, and the coupling nut threads onto the sleeve rather than into the blade, thereby removing the minimum thickness constraint and allowing use of existing blades with various thicknesses.
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 solution effectively reduces vibration amplitudes and prevents fatigue fractures, enabling retrofitting of existing turbine stages without material modifications and minimizing the risk of blade failure, while maintaining mechanical integrity and simplifying production and assembly.
Implementation Method 1
Energy, which causes the blades to vibrate, is withdrawn from the system by means of the coupling elements and dissipated by friction effects.
Data Source
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AI summary
The invention relates to a turbine stage (1) comprising at least one turbine rotor (2) and several turbine blades (3) arranged around the circumference of the turbine rotor (2), as well as at least one coupling element (4), wherein through-bores (5) are formed in a first turbine blade (3') and in a second turbine blade (3ʺ) adjacent to the first, through which the coupling element (4) projects. The coupling element (4) comprises a coupling sleeve (6) and a coupling pin (10) which are screwed together and mechanically couple the turbine blades to one another. By means of the coupling, vibration excitations of the turbine blades (3′, 3ʺ) are effectively dampened.