Variable Bearing Damper Assembly for Gas Turbine Engine
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Solution Overview
Problem
Existing fluid film bearing dampers in gas turbine engines have a fixed geometry, leading to inefficiencies in bearing stability and vibration transmission due to a single operating condition, which is inadequate for managing the bowed rotor effect and varying operational modes, resulting in increased tip leakage, inefficiency, noise, and vibrations during engine start-up and operation.
Innovation Solution
A bearing damper assembly with a variable gap width fluid film damper, where a helical sleeve attached to a squirrel cage threadably engages with a grooved element, allowing the width of the fluid film damper to be adjusted by rotating the helical sleeve into or out of the grooved element, enabling optimal damping coefficient adjustment for different engine modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed geometry fluid film damper is used, then the structure is simple and easy to manufacture, but the damping coefficient cannot be adjusted for different operating conditions, leading to reduced bearing stability and increased vibration transmission
Solution Approach 1:
The patent applies the dynamics principle by making the damper geometry adjustable rather than fixed. The sleeve can be rotated to different angular positions, changing the gap width between the sleeve and housing. This allows the damping coefficient to be dynamically adjusted according to operating conditions such as engine speed and load, resolving the contradiction between adaptability and complexity by introducing a simple rotational adjustment mechanism.
Solution Approach 2:
The patent implements parameter changes by varying the gap width parameter of the fluid film damper. By rotating the sleeve to different angular positions, the effective gap width changes, which directly alters the damping coefficient. This allows optimization of damping performance for different operating conditions without requiring multiple different damper components, thus balancing adaptability with structural simplicity.
2Reliability
If a single gap width is used for the fluid film damper, then the manufacturing is simpler, but the bearing stability is reduced under varying operational modes and bowed rotor conditions
Solution Approach 1:
The patent makes the gap width dynamic rather than static by incorporating a rotatable sleeve mechanism. The gap width can be adjusted to optimal values depending on whether the engine is operating normally or experiencing bowed rotor conditions. This dynamic adjustment capability improves bearing stability across varying operational modes while maintaining a relatively simple manufacturing process compared to active control systems.
3Ease of operation
If the fluid film damper is supplied with oil continuously, then vibration damping is maintained, but the device operates in a binary on/off state without fine control over damping levels
Solution Approach 1:
The patent changes the control parameter from binary (oil supplied/not supplied) to continuous (gap width adjustment). By rotating the sleeve to different angular positions, the operator can finely adjust the gap width and thus the damping coefficient. This provides graduated control over damping levels without requiring complex electronic control systems or multiple valves, maintaining ease of operation while avoiding excessive complexity.
4Productivity
If a fixed damping coefficient is used, then the device is simpler to design, but tip leakage and engine inefficiency increase during bowed rotor start-up
Solution Approach 1:
The patent applies dynamics by enabling the gap width to change during the start-up process. During bowed rotor start-up, the gap can be adjusted to an optimal value that reduces tip leakage and improves engine efficiency. As the engine reaches operating speed and the rotor straightens, the gap can be adjusted again. This dynamic adjustment reduces overall start-up time and improves efficiency without requiring a complex active control system.
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 variable gap width fluid film damper reduces engine start-up time and enhances efficiency by optimizing the damping coefficient for specific operational conditions, minimizing vibrations and tip leakage, and reducing noise.
Implementation Method 1
Fluid film damper (124) is configured to dampen relative vibrations between the inner sleeve (86) and the outer sleeve (84) by absorbing the vibrations
Implementation Method 2
A film of liquid, such as oil, is supplied to an annulus disposed between the stationary housing and the squirrel cage. The film of oil reduces or damps engine vibration and the transmission of vibrations from the bearing to the engine structure
Implementation Method 3
The inner sleeve (86) includes a threaded portion (126) that is threadably engaged with an actuator (118). Rotation of the inner sleeve (86) by the actuator (118) causes the inner sleeve (86) to be axially displaced relative to the outer sleeve (84)
Data Source
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AI summary
A bearing damper assembly (82) for a bearing compartment (50) of a gas turbine engine (10) includes a squirrel cage (98), a bearing support (64), an outer sleeve (84), and an inner sleeve (86). The bearing support (64) is disposed radially outward from a portion of the squirrel cage (98). The outer sleeve (84) extends axially from the bearing support (64). The inner sleeve (86) is attached to the squirrel cage (98) and is disposed radially inward from the outer sleeve (84). An outward surface (100) of the inner sleeve( 96) has a first contoured portion (104) having a first axially extending contour and an inner surface (94) of the outer sleeve (84) has a second contoured portion (96) having a second axially extending contour. The outward surface (100) of the inner sleeve (96) and the inner surface (94) of the outer sleeve (84) define a gap (88) extending between the first contoured portion (104) and the second contoured portion (96). The gap (88) forms a fluid damper (124).