Zigzag Shroud Damping Gaps for Turbo Machine Vibration Control
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Solution Overview
Problem
Turbo machines, particularly gas turbines, face challenges in minimizing sealing gaps and reducing vibrations due to high operating speeds, which affect efficiency and coupling rigidity between blades.
Innovation Solution
A shroud with a zigzag-shaped separation gap featuring multiple damping gaps angled relative to the rotor axis and connection gaps, allowing for increased damping friction and improved coupling rigidity, along with adjustable configurations for resonance control and reduced sealing gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the sealing gap between rotating blades and stationary engine housing is minimized using a conventional shroud, then the efficiency of the engine is improved, but the vibrations in the main operating region increase due to high operating speeds
Solution Approach 1:
The separation gap is segmented into multiple damping gaps (at least three) distributed around the circumference, each capable of providing friction damping. This segmentation allows the shroud to effectively damp vibrations across different frequencies while maintaining the sealing function, resolving the contradiction between efficiency and vibration reduction.
Solution Approach 2:
The damping gaps are designed to dynamically adjust their gap width during rotation, reducing until the gap walls rest against one another under operating conditions. This dynamic behavior allows the structure to adapt to varying operating speeds and temperatures, providing consistent vibration damping while maintaining sealing efficiency.
2Productivity
If the operating speed of the turbo machine is increased to improve productivity, then the power output increases, but the vibrations arising from fundamental characteristic frequencies of the bladed disk increase
Solution Approach 1:
The invention utilizes mechanical vibration damping through the damping gaps, where the friction between gap walls during relative motion dissipates vibrational energy. This converts harmful vibrations into heat, allowing the turbo machine to operate at high speeds without excessive vibrations from blade pass frequencies and fundamental characteristic frequencies.
Solution Approach 2:
The friction that would normally be considered a loss mechanism is converted into a beneficial vibration damping mechanism. The friction surfaces in the damping gaps actively dissipate vibrational energy, transforming the harmful effect of friction into a useful vibration control mechanism that enables high-speed operation.
3Object-affected harmful factors
If a Z-shaped separation gap with two damping gaps is used to damp vibrations, then some vibration damping is achieved, but the contact surface available for damping friction is insufficient at high operating speeds
Solution Approach 1:
The separation gap is divided into at least three distinct damping gaps distributed around the circumference, significantly increasing the total contact surface area available for friction damping compared to conventional two-gap designs. This segmentation ensures adequate damping capacity even at high operating speeds where vibration amplitudes are larger.
4Strength
If the shroud is made rigid to improve coupling rigidity of adjacent blades, then the structural stability improves, but the ability to accommodate thermal expansion and maintain resonance-free operation decreases
Solution Approach 1:
The shroud incorporates dynamic elements through the damping gaps that can open and close during operation. When gaps are closed, they provide rigid coupling and vibration damping; when open, they allow thermal expansion and kinematic adjustment. This dynamic behavior enables the shroud to maintain both rigidity and adaptability throughout the operating cycle.
Solution Approach 2:
The gap width parameter of the damping gaps is designed to change during operation, reducing until gap walls rest against one another. This parameter change allows the structure to transition between different stiffness states, providing rigid coupling when needed while accommodating thermal expansion and maintaining resonance-free operation across varying operating conditions.
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 ensures predominantly resonance-free operation and enhanced coupling rigidity, leading to improved efficiency and power flow distribution within the turbo machine, while allowing for unhindered thermal expansion and reduced production costs through modular design.
Implementation Method 1
the two damping gaps offer a friction surface, which makes possible a corresponding damping of friction from vibrations of the integral wheel during operation
Implementation Method 2
the Z crosspiece is formed as an open gap running in the direction of the edges of the shroud. In this way, an unhindered circumferential shift of the shroud is possible, in order to assure a tension-free equilibration of thermal expansion
Data Source
AI summary
A shroud for the rotating blades of a turbo machine, particularly a gas turbine, in which shroud is arranged along the circumference of a row of several rotating blades disposed on a rotor and has at least one separation gap along its circumference. The separation gap is formed in zigzag shape and has at least three damping gaps that are distanced from one another and extend at an angle relative to an axis of rotation of the rotor, and adjacent to these, has connection gaps each connecting damping gaps or extending the latter in the direction of shroud edges, wherein, when the rotor rotates, the gap width of damping gaps is reduced until the gap walls forming the damping gaps come to rest against each other.