Actively Controlled Leaf Seal for Turbomachine
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Solution Overview
Problem
Existing leaf seals for turbomachines have a limited service life, leading to increased operational costs due to frequent replacements and inefficiencies in sealing performance across varying operating conditions.
Innovation Solution
A leaf seal design with actively controlled axial distance adjustment between sealing leaves and end plates, utilizing a device to optimize the blow-down and blow-up effects, minimizing wear and ensuring optimal sealing performance across transient and stationary conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the axial distance between sealing leaves and end plates is fixed, then the structure is simple and manufacturing is easy, but the service life is limited and sealing performance varies under different operating conditions
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed axial distance structure into a dynamically adjustable one. A drive mechanism (motor, gear, screw) enables active control of the axial distance between sealing leaves and end plates, allowing the seal to adapt to varying operating conditions such as different rotational speeds and pressure differentials, thereby extending service life and maintaining sealing performance.
Solution Approach 2:
The patent implements parameter changes by actively modifying the axial distance parameter between sealing leaves and end plates based on operating conditions. The control system adjusts this distance to optimize the blow-down and blow-up effects, ensuring consistent sealing performance across transient and stationary conditions, which directly addresses the limitation of fixed-distance designs.
2Adaptability or versatility
If the axial distance between sealing leaves and end plates is actively adjusted, then the sealing performance is optimized across varying operating conditions, but the device complexity increases
Solution Approach 1:
The patent optimizes sealing performance by actively adjusting the axial distance parameter between sealing leaves and end plates. The control system monitors operating conditions (rotational speed, pressure differential) and modifies the distance to maintain optimal sealing, ensuring consistent performance across transient and stationary conditions despite increased control complexity.
Solution Approach 2:
The patent incorporates feedback mechanisms where sensors detect operating parameters (rotational speed, pressure differential, blade position) and the control system uses this information to adjust the axial distance accordingly. This closed-loop control ensures optimal sealing performance is maintained dynamically, addressing the adaptability requirement while managing complexity through intelligent control.
3Strength
If the sealing leaves are made more rigid to withstand higher pressure differentials, then the pressure resistance improves, but the flexibility and radial freedom of movement are reduced
Solution Approach 1:
The patent applies dynamics by making the axial distance adjustable rather than fixed. This allows the system to optimize the balance between rigidity and flexibility dynamically - increasing distance to reduce contact pressure and wear during high-speed operation, and decreasing distance to enhance sealing during low-speed or high-pressure conditions, thereby maintaining both pressure resistance and radial freedom.
Solution Approach 2:
The patent uses preliminary action by pre-adjusting the axial distance between end plates and sealing leaves based on anticipated operating conditions. The control system proactively modifies the distance to prevent excessive wear or loss of sealing before problems occur, optimizing the rigidity-flexibility balance in advance for different operational scenarios.
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 extends the service life of the leaf seal, reduces wear, and optimizes sealing performance by dynamically adjusting the axial distance, thereby minimizing friction and maintaining effective sealing across a wide range of operating conditions, reducing the need for frequent replacements and lowering operational costs.
Implementation Method 1
a dynamic pressure created during machine operation in the area of the sealing blades on the shaft, causing the blade ends to lift a minimal distance of the order of microns, thereby reducing friction
Implementation Method 2
a spacing between the individual sealing leaves that allows an air gap and an air flow through the seal, which triggers a so-called blow-down or blow-up effect depending on the extent of the air flow. A blow-down effect pushes the sealing leaves against the shaft, while a blow-up effect pushes them away from the shaft
Data Source
Figure 1
Figure 2~3
Figure 3a~3b
AI summary
The seal (3) has multiple metallic sheets (4) which are arranged concentrically around the periphery of a rotor of a turbo engine. The sheets are stung together and mounted on a carrier (6). The seal has a front plate (7) and a rear plate (8), where the both plates are connected with the carrier and extend over the periphery of the seal on both sides of sheets. The seal has a device in the transformation of an axial distance between the seal and the rear plate. The transformation is actively controlled during the operation of the turbo engine.