Self-Pressurizing Squeeze Film Damper Against Cavitation
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Solution Overview
Problem
Existing fluid damping structures in gas turbine engines face challenges in maintaining consistent pressure within the damping chamber, leading to potential air ingestion and cavitation during cyclical orbital motion of shafts, which compromises their effectiveness in reducing lateral forces and stresses on bearings.
Innovation Solution
A fluid damping structure with lateral chambers and a self-pressurizing mechanism, utilizing a network of seals and passages to maintain uniform fluid pressure and prevent air ingress, ensures consistent damping fluid flow and operation even under conditions of cyclical shaft motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluid damping structure is used to reduce lateral forces on bearings, then the effectiveness in reducing vibrations is improved, but air ingestion and cavitation occur due to pressure instability in the damping chamber
Solution Approach 1:
The damping chamber is pre-filled with damping fluid to a controlled level before operation. This preliminary action ensures that the chamber maintains sufficient fluid volume to prevent air ingestion during shaft orbital motion, while the pre-established fluid column provides initial pressure stability to prevent cavitation during damping operations.
Solution Approach 2:
A breathable membrane is introduced as an intermediary element between the damping chamber and the fluid supply system. This membrane allows pressure equalization while preventing direct air ingress into the damping chamber, thus maintaining pressure stability without compromising the damping fluid seal.
2Object-affected harmful factors
If the damping chamber is filled with damping fluid to prevent air ingestion, then air ingestion is prevented, but the complexity of the fluid management system increases
Solution Approach 1:
The damping chamber is designed to be self-regulating through the breathable membrane, which automatically equalizes pressure differences during shaft orbital motion without requiring external control systems. The chamber self-manages pressure stability through the membrane's inherent properties, eliminating the need for complex active fluid management.
Solution Approach 2:
The complex active fluid management system is extracted and replaced with a passive breathable membrane that performs the pressure regulation function. This extraction simplifies the overall system by removing sensors, actuators, and control logic while maintaining the essential pressure stability function through the membrane's physical properties.
3Adaptability or versatility
If the damping fluid pressure is allowed to vary during shaft orbital motion, then the system responds dynamically to shaft position, but pressure uniformity is compromised leading to cavitation
Solution Approach 1:
The breathable membrane creates a pressure equalization mechanism that maintains uniform pressure throughout the damping chamber during shaft orbital motion. By allowing pressure to equalize across the membrane surface, the system achieves equipotential pressure distribution, preventing localized low-pressure zones that would cause cavitation while maintaining dynamic adaptability.
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 prevents cavitation and maintains damping fluid pressure uniformity, enhancing the performance and reliability of the fluid damping structure in reducing shaft-induced vibrations and stresses on bearings.
Implementation Method 1
The fluid damper structure is a hydrodynamic system wherein a continuously flowing stream of damping fluid (e.g., oil) is supplied to an annular volume formed between the non-rotating outer bearing race (or housing) and the engine support case for the purpose of absorbing and reducing the transverse movement induced by shaft imbalance
Implementation Method 2
U.S. Patent No. 5,344,239 discloses a squeeze film damper with annular end plenums
Data Source
Figure 1
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Figure 4~5A
AI summary
A fluid damping structure (68) is provided that includes an inner annular element (64), an outer annular element (66), a first outer seal (162), a second outer seal (164), an inner seal (166), a damping chamber (70), a supply plenum (160), a fill port (174), and a plurality of fluid passages (140). The plurality of fluid passages (140) is disposed in at least one of the inner annular element (64) or the inner seal (166). The fluid damping structure (68) is configured such that one or more of the fluid passages (140) is disposed in an open configuration when a local damping fluid pressure within the damping chamber (70) is less than a local damping fluid pressure in an adjacent region of the supply plenum (160), and the one or more of the fluid passages (140) is disposed in a closed configuration when the local damping fluid pressure within the damping chamber (70) is greater than the local damping fluid pressure in the adjacent region of the supply plenum (160).