Bellows Valve Assembly for Pressure-Balanced Sealing
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Solution Overview
Problem
Valve assemblies in gas turbine engines face issues with parasitic leakage due to unbalanced forces on metal bellows, leading to lateral distortion and reduced service life, which increases maintenance costs and friction between moving components.
Innovation Solution
Incorporating a bellows within the valve member and actuator body with an orifice that allows pressure balance between the control chamber and outer volume, reducing unbalanced forces and eliminating the need for sliding seals, thereby enhancing the cyclic life and reducing friction and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal bellows is used to seal the control chamber at high temperatures, then thermal resistance is improved, but unbalanced forces cause lateral distortion and reduced cyclic life
Solution Approach 1:
The bellows is divided into two distinct chambers: a control chamber for actuation and an outer volume for pressure balancing. This segmentation allows independent pressure management, enabling the bellows to withstand high temperatures while maintaining structural integrity and extending cyclic life through balanced forces.
Solution Approach 2:
The orifice acts as an intermediary element connecting the control chamber and outer volume. It mediates pressure distribution by allowing fluid communication between the two chambers, balancing forces on the bellows and preventing lateral distortion during thermal operation.
2Reliability
If traditional sliding seals are used to seal the control chamber, then sealing is achieved, but friction between moving components increases
Solution Approach 1:
The mechanical sliding seal system is replaced with a bellows-based sealing mechanism. The bellows provides sealing through its flexible membrane structure, eliminating the need for sliding contact between seal components and thereby dramatically reducing friction while maintaining reliable sealing of the control chamber.
Solution Approach 2:
The bellows functions as a flexible shell that seals the control chamber without requiring sliding seals. Its flexible membrane structure accommodates movement while maintaining sealing integrity, replacing traditional friction-based mechanical seals with a low-friction flexible barrier.
3Force
If pressure difference between control chamber and outer volume is maintained, then actuation force is improved, but unbalanced forces cause lateral distortion
Solution Approach 1:
The bellows is segmented into two pressure zones (control chamber and outer volume) that can be independently managed. This allows maintenance of pressure difference for actuation while balancing forces through the orifice connection, preventing lateral distortion.
Solution Approach 2:
The orifice creates a pressure equilibrium pathway between the control chamber and outer volume. This equipotential connection balances radial forces on the bellows walls, preventing lateral distortion while allowing axial pressure difference to provide actuation force.
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 design significantly reduces parasitic leakage, increases the service life of the valve assembly by balancing pressures, and decreases maintenance costs through reduced wear and tear, while allowing for quicker response times and improved thermal performance.
Implementation Method 1
The at least one orifice fluidly communicates the control chamber with the outer volume. The at least one orifice may allow flow of a fluid between the control chamber and the outer volume, and therefore, allow a pressure inside the control chamber to be balanced with a pressure outside the control chamber
Implementation Method 2
The bellows is expandable from a first configuration in which the valve member is in the first position to a second configuration in which the valve member is in the second position
Data Source
AI summary
A valve assembly includes a fluid flow passage, a valve seat, and an actuator assembly. The actuator assembly includes an actuator body stationary relative to the valve seat and a valve member moveable relative to the valve seat between a first position in which the valve member engages the valve seat, and a second position in which the valve member is remote from the valve seat. The valve member includes at least one orifice extending therethrough. The actuator assembly further includes a bellows attached to the valve member and to the actuator body. An interior surface of the bellows, the actuator body, and the valve member define a control chamber therebetween. An exterior surface of the bellows and the valve member define an outer volume therebetween such that the outer volume is around the control chamber. The at least one orifice fluidly communicates the control chamber with the outer volume.