Gas Bearing Speed Control for Compressor Sub-Synchronous Stability
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Solution Overview
Problem
Gas bearings in HVACR compressors experience sub-synchronous instabilities and potential failure due to unstable support when operated at higher speeds or under pressure variations, leading to potential damage.
Innovation Solution
A controller determines inlet and outlet pressures of the gas bearings, calculates a maximum speed limit based on these pressures, and adjusts compressor operation to maintain stable support by regulating gas supply and discharge pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor operates at higher speeds to improve productivity, then the cooling capacity increases, but the gas bearing becomes unstable and may fail
Solution Approach 1:
The controller continuously monitors the actual speed of the compressor and compares it to the calculated maximum speed limit. When the actual speed approaches or exceeds the maximum limit, the controller adjusts the operation to maintain stable gas bearing support. This closed-loop feedback mechanism enables the system to operate at high speeds while preventing bearing instability.
Solution Approach 2:
The system dynamically calculates and adjusts the maximum speed limit parameter based on changing operating conditions, specifically the inlet and outlet pressures of the gas bearing. By modifying this critical parameter in real-time, the system adapts to varying load conditions and maintains optimal bearing stability across different operating points.
2Reliability
If the compressor speed is limited to maintain gas bearing stability, then reliability improves, but productivity decreases
Solution Approach 1:
Rather than imposing a fixed speed limit, the system dynamically determines the maximum speed limit based on real-time pressure measurements from the gas bearing. This dynamic approach allows the compressor to operate at the highest possible speed that maintains bearing stability, optimizing the balance between reliability and productivity under varying operating conditions.
Solution Approach 2:
The system changes the operational parameter (maximum speed limit) based on the actual gas bearing pressure conditions. When pressures indicate stable bearing operation, higher speeds are permitted; when pressures suggest instability risk, the speed limit is reduced. This adaptive parameter adjustment maximizes productivity while ensuring reliability.
3Reliability
If compressed gas pressure is increased to improve gas bearing support, then bearing stability improves, but the risk of sub-synchronous instabilities increases
Solution Approach 1:
The system uses pressure feedback from both the inlet and outlet of the gas bearing to determine the appropriate maximum speed limit. This feedback mechanism allows the system to identify optimal operating conditions where sufficient bearing support is provided without exceeding the pressure thresholds that trigger sub-synchronous instabilities.
Solution Approach 2:
Instead of relying solely on mechanical pressure regulation, the system uses electronic control to monitor pressure conditions and adjust compressor operation. This substitution of mechanical control with electronic sensing and control allows for more precise management of gas bearing pressures, avoiding the harmful nonlinear effects of excessive pressurization.
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
Stabilizes gas bearing operation, preventing failures and ensuring safe operation of HVACR compressors by maintaining the compressor speed within the calculated maximum limit.
Implementation Method 1
A bearing can be a gas bearing that utilizes compressed gas to provide support to its moving/rotating component
Data Source
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AI summary
A heating, ventilation, air conditioning, and refrigeration (HVACR) system includes a compressor (100) with a gas bearing (140A,140B) supplied with compressed gas and a controller (190). The controller is configured to determine an inlet pressure and outlet pressure of the gas bearing, determine a maximum speed limit based on the inlet pressure and the outlet pressure, and prevent the compressor from operating at a speed that is greater than the maximum speed limit. A method of controlling a compressor includes calculating a maximum speed limit based on an inlet pressure and an outlet pressure of the gas bearing. The method also includes in response to determining that a speed setting is greater than the maximum speed limit, adjusting operation of the compressor such that a speed of the compressor is at or below the maximum speed limit.