Stepped Compressor Seal Assembly for Variable Clearance Control
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Solution Overview
Problem
Magnetic bearing compressors face challenges in maintaining efficient operation during start-up and shut-down phases due to potential damage from upstream movement tightening the clearance between the impeller and its shroud, and opposite movement reducing efficiency by opening clearance, which leads to fluid leakage and reduced performance.
Innovation Solution
A seal assembly with radially stepped surfaces and projections is used, where actuators move the seal lands and seals between axial positions to increase clearance during start-up and shut-down, preventing contact and reducing fluid leakage, and maintaining efficient operation by adjusting seal clearance based on compressor operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic bearings are used to support the shaft, then compressor efficiency is improved during normal operation, but damage risk increases during start-up and shut-down due to upstream movement tightening clearance between impeller and shroud
Solution Approach 1:
The seal assembly incorporates an actuator that dynamically adjusts the axial position of the seal land relative to the seal during different operating conditions. During start-up and shut-down, the actuator moves the seal land to increase clearance and prevent contact, while during normal operation, the seal land returns to its original position to maintain efficient sealing, thus adapting to different operational states
Solution Approach 2:
The actuator is configured to proactively adjust the seal clearance before damage can occur during start-up and shut-down phases. By detecting upcoming operational changes, the system预先 increases clearance to prevent impeller-shroud contact, rather than reacting after damage has occurred
2Reliability
If seal clearance is increased to prevent contact during start-up and shut-down, then damage risk is reduced, but fluid leakage increases and efficiency decreases
Solution Approach 1:
The seal assembly uses an actuator to dynamically adjust the axial position of the seal land, creating variable clearance that adapts to operating conditions. During start-up and shut-down, clearance is increased to prevent contact; during normal operation, clearance returns to optimal sealing dimensions, thus balancing protection needs with efficiency requirements
Solution Approach 2:
The system changes the physical parameter of seal clearance based on operational state. The actuator modifies the axial distance between the seal land and seal, transitioning from a fixed clearance design to a variable clearance system that optimizes both protection and efficiency for different operating phases
3Device complexity
If a fixed seal assembly is used, then device complexity is reduced, but the ability to adapt to different operating conditions is limited
Solution Approach 1:
The seal assembly incorporates an actuator that enables dynamic adjustment of the seal land's axial position in response to detected operating conditions. This transforms a static, simple structure into an adaptive system that automatically modifies seal clearance during different operational phases, enhancing versatility without substantially complicating the overall design
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 reduces fluid leakage and enhances compressor efficiency by dynamically adjusting seal clearance, ensuring smooth operation and preventing damage during start-up and shut-down phases, thereby improving the overall performance of electric motor-driven magnetic bearing compressors.
Implementation Method 1
At least one electromagnetic bearing supports the shaft
Data Source
Figure 1
Figure 2
Figure 3A~4B
AI summary
A seal assembly 96; 98; 100 for a compressor 22 includes at least one impeller 60; 62. At least one seal land 102; 110; 118 is associated with the impeller 60, 62 including a plurality of radially stepped surfaces 102A, 102B, 102C; 110A, 110B, 110C; 118A, 118B, 118C. A seal 104; 112; 120 is associated with each of at least one seal lands 102; 110; 118. The seal includes a plurality of radially stepped projections 104A, 104B, 104C; 112A, 112B, 112C; 120A, 120B, 120C corresponding to the plurality of radially stepped surfaces 102A, 102B, 102C; 110A, 110B, 110C; 118A, 118B, 118C on at least one seal land 102; 110; 118. At least one actuator 108; 116; 124 is configured to move at least one seal land 102; 110; 118 relative to the seal 104; 112; 120.