Turbo Compressor Magnetic Thrust-Bearing Control for Impeller Clearance
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Solution Overview
Problem
In turbo compressors with open impellers and magnetic bearings, the low bearing stiffness leads to increased tip clearance risk during start-up or load changes, necessitating larger gaps to prevent contact, which in turn increases energy consumption and reduces efficiency due to gas leakage.
Innovation Solution
A controller calculates the axial thrust load based on pressure and temperature measurements, adjusting the axial support position of the rotary shaft to minimize the gap between the impeller and shroud while avoiding contact, using sensors and correcting means to dynamically control the gap during transient operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between the impeller and shroud is increased to avoid contact during start-up or load changes, then the reliability is improved, but the compression efficiency deteriorates due to increased gas leakage
Solution Approach 1:
The patent applies dynamics by making the axial position of the rotary shaft adjustable through the thrust magnetic bearing. The axial position is dynamically changed based on the calculated axial thrust load to maintain an optimal gap between the impeller and shroud, preventing contact during transient operations while minimizing gas leakage during stable operation.
Solution Approach 2:
The patent changes the parameter of axial position of the rotary shaft based on the calculated axial thrust load. By adjusting this parameter dynamically, the system optimizes the gap between impeller and shroud to prevent contact during high-load transient operations while minimizing gas leakage during stable operation.
2Loss of energy
If the gap between the impeller and shroud is minimized to reduce gas leakage, then the compression efficiency is improved, but the risk of contact between impeller and shroud increases during transient operations
Solution Approach 1:
The patent implements feedback by calculating the axial thrust load based on pressure and temperature measurements, then using this calculated load to adjust the axial position of the rotary shaft. This closed-loop control ensures the gap between impeller and shroud is optimized to prevent contact while minimizing gas leakage.
Solution Approach 2:
The patent applies preliminary action by calculating the axial thrust load in advance and adjusting the axial position of the rotary shaft before contact can occur during transient operations. This proactive adjustment prevents contact while maintaining minimal gap for efficiency.
3Reliability
If the bearing stiffness is increased to reduce axial shaft movement, then the reliability is improved, but the device complexity increases due to replacement of magnetic bearings
Solution Approach 1:
The patent replaces the mechanical bearing system with a magnetic bearing system that uses electromagnetic fields to support the rotary shaft. This substitution eliminates mechanical contact, reduces friction and wear, and allows for dynamic adjustment of axial position through electromagnetic control, thereby maintaining reliability while enabling precise gap control.
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 approach reduces gas leakage, enhances compression efficiency, and enlarges the safe operation region by maintaining the minimum necessary gap between the impeller and shroud, thereby improving the performance and efficiency of the turbo compressor and turbo chiller.
Implementation Method 1
a rotary shaft which is supported by a radial magnetic bearing and a thrust magnetic bearing
Data Source
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AI summary
The purpose of the present invention is to provide: a turbo compressor which is provided with an open impeller and has the minimal gap between the shroud and the impeller such that efficiency is improved and the safe operating region is enlarged; and a turbo chiller using the same. The turbo compressor (1) is provided with an open impeller (3 and 4) with a shroud (16 and 17) provided on the side of a casing (6), and the rotary shaft (5) is supported by a radial magnetic bearing (7 and 8) and a magnetic thrust bearing (9 and 10). The turbo compressor (1) is provided with a control unit (22) that comprises: a load calculating means (23) that calculates the axial thrust load generated by the pressure distribution of the compressor (1); and an axial support position control means (24) that controls a gap (S) between the impeller (3 and 4) and the shroud (16 and 17) to be a target gap (S1) by varying, on the basis of the axial thrust load, the axial support position of the rotary shaft (5) due to the magnetic thrust bearing (9 and 10).