Counter-Rotating Engine Damper Mitigates Vibratory Modes
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Solution Overview
Problem
Counter-rotating turbine engines experience increased vibratory modes due to the sum of inner and outer rotor speeds, which limits engine speeds and efficiency, and existing solutions to mitigate these modes often require heavier structures that offset performance improvements.
Innovation Solution
A damper structure is integrated into the gas turbine engine, comprising an annular ring with springing properties that generates an outward force along the radial direction, coupled to the outer drum and airfoil, to mitigate vibratory modes by interdigitation and extension of the outer drum or shroud over other rotor assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If counter-rotating turbine arrangement is implemented to increase engine performance and efficiency, then power output and fuel efficiency are improved, but vibratory modes are increased due to the sum of inner and outer rotor speeds
Solution Approach 1:
A damper structure is introduced as an intermediary component between the outer drum and the rotor assembly. This damper structure absorbs and mitigates the vibratory modes generated by the counter-rotating arrangement, allowing the engine to maintain the performance benefits while reducing the harmful vibrations to acceptable levels.
Solution Approach 2:
The natural frequency of the outer drum or shroud is modified by changing its structural parameters (such as thickness, material properties, or geometric configuration). This parameter change shifts the natural frequency away from the excitation frequencies caused by the counter-rotating rotors, thereby reducing resonant vibrations and allowing higher operating speeds.
2Object-affected harmful factors
If larger and/or heavier structures are added to mitigate vibratory modes, then certain vibratory modes are reduced, but efficiency and performance improvements are offset by increased weight
Solution Approach 1:
The damper structure utilizes flexible elements or thin-walled structures that provide vibration mitigation through elastic deformation rather than through mass. This approach achieves effective vibration control with minimal additional weight, preserving the performance advantages of the counter-rotating configuration.
Solution Approach 2:
Instead of increasing structural mass to reduce vibrations, the natural frequency of the existing structure is modified through parameter changes (such as wall thickness, material modulus, or geometric dimensions). This allows vibration control to be achieved without adding significant weight, maintaining the efficiency benefits of the counter-rotating design.
3Volume of moving object
If relatively larger diameters and small radial depths of overhanging shrouds are used, then packaging is improved, but natural frequencies are reduced thus limiting engine speeds
Solution Approach 1:
The natural frequency of the overhanging shroud or drum is increased by modifying its structural parameters (such as increasing thickness, using higher modulus materials, or optimizing geometric configuration). This parameter change raises the natural frequency above the operating speed range, eliminating resonance issues and enabling the engine to operate at higher speeds while maintaining the compact packaging benefits.
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 damper structure reduces low-order vibrations, enabling increased engine efficiency, performance, and operational capabilities at higher rotational speeds, while reducing weight and packaging, and improving fuel efficiency and power output.
Implementation Method 1
the damper structure defines springing properties generating an outward force along the radial direction
Implementation Method 2
A damper structure is coupled to one or more of the outer drum or the outer drum airfoil... reduces low-order vibrations
Data Source
AI summary
A gas turbine engine including a first rotor assembly is generally provided. The first rotor assembly includes outer drum and an outer drum airfoil. The outer drum airfoil is coupled to the outer drum and extended inward along a radial direction. A damper structure is coupled to one or more of the outer drum or the outer drum airfoil.