Rotating Machine Seal Structure for Secure Gap and Low Leakage
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Solution Overview
Problem
Existing sealing devices in rotating machines face challenges in securing a reliable seal gap between the rotor and the movable sealing member during activation and deactivation, while also minimizing fluid leakage during operation. The biasing force required to counteract the self-weight of the sealing member is difficult to set, especially as the dimension of the sealing member increases.
Innovation Solution
The sealing device incorporates a movable sealing member with a base portion, a rib protruding radially outward, and a seal fin protruding radially inward. The rib features a notch portion where the biasing spring is disposed, allowing for efficient biasing and movement of the sealing member. This configuration helps in reducing the self-weight of the sealing member while maintaining rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the biasing force of the elastic body is increased to secure a seal gap during activation and deactivation, then the seal gap is reliably secured, but it becomes difficult to displace the sealing member to the radial inner side during operation
Solution Approach 1:
The sealing member is divided into multiple segments (first sealing member and second sealing member) that can move independently. This segmentation allows each segment to respond differently to biasing forces and fluid pressure, enabling the first sealing member to be displaced inward during operation while the second sealing member maintains the seal gap during activation and deactivation.
Solution Approach 2:
The sealing device employs dynamic biasing forces with different magnitudes for different operational states. A first biasing member provides a first biasing force during activation and deactivation to secure the seal gap, while a second biasing member provides a second biasing force during operation that allows displacement to the radial inner side. This dynamic adjustment of biasing forces resolves the contradiction between maintaining seal gap and enabling operational displacement.
2Reliability
If the dimension of the sealing member in the radial direction is increased to reduce fluid leakage, then the sealing performance is improved, but the self-weight increases making it difficult to set the biasing force
Solution Approach 1:
The sealing member is segmented into multiple parts (first sealing member and second sealing member) along the radial direction. This segmentation reduces the self-weight of each individual sealing member while maintaining the overall sealing dimension. The reduced weight of each segment makes it feasible to set appropriate biasing forces that can both secure the seal gap and allow operational displacement.
Solution Approach 2:
The system uses dynamically adjustable biasing forces through multiple biasing members that can independently control different sealing segments. This allows the biasing force to be optimized for each segment's weight and function, enabling large radial sealing dimensions for leakage reduction while keeping individual segment weights manageable through proportional biasing forces.
3Ease of operation
If the biasing force is decreased to allow displacement during operation, then the operational performance is improved, but the seal gap cannot be secured during activation and deactivation
Solution Approach 1:
The sealing device employs a dynamic biasing system with multiple biasing members that can provide different biasing forces for different operational states. During activation and deactivation, the biasing members provide sufficient force to secure the seal gap. During operation, the biasing force is adjusted to allow displacement to the radial inner side. This dynamic control resolves the contradiction between operational displacement capability and seal gap security.
Solution Approach 2:
The sealing member is divided into segments that can respond independently to biasing forces. This segmentation allows different portions of the sealing system to have different displacement characteristics, enabling some segments to maintain seal gap during activation/deactivation while other segments can displace during operation.
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 configuration effectively secures the seal gap between the rotating member and the sealing member during machine activation and deactivation, and reduces fluid leakage during operation by optimizing the biasing force and structural integrity of the sealing member.
Implementation Method 1
a biasing member that biases the sealing member toward the radial outer side
Implementation Method 2
a working fluid (for example, working steam) on the high-pressure side circulates around a back surface of the sealing member on the radial outer side, so that a back-surface pressure is applied to the sealing member
Data Source
AI summary
A sealing device including: a sealing member that is disposed between a rotating member of a rotating machine and a stationary member disposed on the outer side of the rotating member in the radial direction of the rotating member, and that creates a seal between the rotating member and the stationary member; and a biasing member that biases the sealing member toward the radially outer side. The sealing member has a base extending in the circumferential direction of the rotating member, a rib that extends in the circumferential direction and protrudes outward in the radial direction from the base, and a seal fin that extends in the circumferential direction and protrudes inward in the radial direction of the rotating member from the base. The rib has a cut-away part in which the biasing member is disposed between one end and the other end of the rib in the circumferential direction.