Actuated Stepped Seal Assembly for Compressor Clearance Control
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Solution Overview
Problem
Magnetic bearings in compressors face challenges in maintaining optimal seal clearance during start-up and shut-down phases, which can lead to inefficiencies and potential damage due to excessive radial movement of the shaft.
Innovation Solution
A seal assembly with radially stepped surfaces and projections, actuated to adjust clearance between the impeller and housing, maintains a labyrinth seal during normal operation and increases clearance during start-up and shut-down to prevent contact and fluid leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic bearings are used to support the compressor shaft, then radial and axial positioning is improved during normal operation, but seal clearance cannot be optimized during start-up and shut-down phases
Solution Approach 1:
The seal assembly incorporates an actuator that dynamically adjusts the seal land position based on operational phase. During start-up and shut-down, the actuator moves the seal land to increase clearance; during normal operation, it maintains optimal sealing position. This dynamic adjustment resolves the contradiction between stable shaft positioning and adaptive seal clearance.
Solution Approach 2:
The actuator is configured to adjust seal clearance in advance during start-up and shut-down phases before excessive shaft movement occurs. By proactively increasing clearance during these transitional phases, the system prevents potential seal contact and damage before they can occur, while maintaining tight clearance during normal operation for optimal sealing.
2Loss of energy
If seal clearance is reduced to prevent fluid leakage, then sealing efficiency is improved, but shaft movement during start-up and shut-down causes seal contact and potential damage
Solution Approach 1:
The seal assembly transitions from a static clearance design to a dynamic one where the actuator adjusts seal land position based on operational conditions. During normal operation, tight clearance minimizes fluid leakage; during start-up and shut-down, increased clearance prevents seal contact, thus resolving the contradiction between sealing efficiency and seal durability.
Solution Approach 2:
The system changes the clearance parameter dynamically based on operational phase. The actuator modifies the axial position of the seal land, transitioning the clearance from small (during normal operation) to large (during start-up and shut-down). This parameter change allows the system to optimize for both minimal leakage and seal protection at different times.
3Productivity
If tight seal clearance is maintained to improve efficiency, then fluid leakage is reduced, but excessive shaft radial movement during transitional phases causes seal contact
Solution Approach 1:
The actuator provides dynamic control of seal clearance, allowing the system to maintain tight clearance for optimal efficiency during normal operation while increasing clearance during start-up and shut-down to prevent harmful seal contact. This dynamic adjustment eliminates the need to compromise between efficiency and protection.
Solution Approach 2:
The actuator applies a preliminary counter-action by increasing seal clearance before excessive shaft movement can occur during start-up and shut-down phases. This preventive measure counteracts the potential harmful effect of seal contact while maintaining efficient tight clearance during normal operation, thus protecting the seal without sacrificing productivity.
Data Source
AI summary
A seal assembly for a compressor includes at least one impeller. At least one seal land is associated with the impeller including a plurality of radially stepped surfaces. A seal is associated with each of at least one seal lands. The seal includes a plurality of radially stepped projections corresponding to the plurality of radially stepped surfaces on at least one seal land. At least one actuator is configured to move at least one seal land relative to the seal.