Method and system for controlling differential pressure for an externally pressurized gas bearing apparatus
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Solution Overview
Problem
Existing HVACR systems face challenges in maintaining stable operation of compressors at high rotational speeds due to fluctuations in differential pressure across gas bearings, which can lead to non-synchronous rotation and potential damage, especially when using oil-free magnetic or hydrodynamic bearings.
Innovation Solution
A gas bearing system that utilizes a pressurized fluid to form a thin film between the bearing and the shaft, with a pressure reducer to control and maintain differential pressure, using components like venturis, eductors, or ejectors to adjust outlet pressure and ensure stable shaft support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gas bearing is used to support the compressor shaft at high rotational speeds, then oil-free operation is achieved, but differential pressure fluctuations cause non-synchronous rotation and potential damage
Solution Approach 1:
The system employs feedback control by sensing the actual differential pressure across the gas bearing and comparing it to a desired setpoint. The controller adjusts the outlet pressure of the gas bearing based on this feedback to maintain stable differential pressure, preventing non-synchronous rotation and ensuring reliable shaft support at high speeds
Solution Approach 2:
The system dynamically changes the outlet pressure parameter of the gas bearing to maintain optimal differential pressure. By adjusting the outlet pressure in response to operating conditions, the system maintains stable shaft support while operating at high rotational speeds without oil lubrication
2Reliability
If the outlet pressure of the gas bearing is increased to maintain differential pressure, then shaft support stability improves, but the complexity of the pressure control system increases
Solution Approach 1:
A feedback control system senses differential pressure and automatically adjusts outlet pressure, eliminating the need for complex manual control mechanisms while maintaining shaft support stability
Solution Approach 2:
The pressure control system serves itself by using the differential pressure sensor output to automatically regulate the outlet pressure, reducing the need for external complex control mechanisms and simplifying the overall system architecture
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 system effectively maintains stable shaft position and prevents non-synchronous rotation by controlling differential pressure, ensuring reliable operation of compressors at high speeds and reducing the risk of damage from thermal expansion and rotor whirl.
Implementation Method 1
uses a pressurized fluid to form a thin film between the gas bearing and the shaft
Implementation Method 2
a pressure reducer to control and maintain differential pressure, using components like venturis, eductors, or ejectors to adjust outlet pressure
Data Source
AI summary
A heat transfer circuit includes a compressor, a condenser, an expander, and an evaporator that are fluidly connected together. The compressor includes a housing and a shaft rotatable relative to the housing to compress a working fluid received at a suction inlet, in which the shaft is supported by a gas bearing, and the gas bearing including a bearing housing having a fluid inlet and an outlet. A high pressure gas source is fluidly connected to the fluid inlet of the bearing housing for supplying high pressure fluid to the fluid inlet of the gas bearing such that the gas bearing supports the shaft when the shaft is rotating. A pressure reducer is connected to the outlet of the gas bearing is provided for reducing a vent pressure of the gas bearing.