Screw Compressor/Expander Controlled Shutdown to Prevent Rotor Damage
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Solution Overview
Problem
Compressor/expander machines experience damage at the high-pressure end surfaces of screw runners due to pressure differences, reversal of rotary direction, and lubrication interruptions, leading to issues like abrasion, heating, and overheating.
Innovation Solution
An operating tax unit gradually reduces the speed of the engine/generator unit to a low-speed range, using a sequence of speed data that forms a brake ramp with specific gradients to prevent damage, and maintains this speed to ensure no acceleration, with a lubricant support film to prevent contact between high-pressure end surfaces and end wall surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the compressor/expander machine is switched off abruptly, then the shutdown time is reduced, but damage occurs to the screw rotor due to pressure differences and lubrication interruption
Solution Approach 1:
The control unit initiates a deceleration ramp before complete shutdown to gradually reduce screw rotor speed to a lowest speed range, preventing damage caused by abrupt shutdown. This preliminary speed reduction ensures lubrication is maintained and pressure differences are minimized before the shutdown occurs.
Solution Approach 2:
The system dynamically adjusts the screw rotor speed during shutdown by implementing a controlled deceleration process. The motor/generator unit speed is reduced according to a predetermined deceleration ramp, transitioning from normal operating speed to a lowest speed range that prevents damage while minimizing shutdown time.
2Reliability
If the screw rotor speed is reduced to the lowest speed range, then damage is prevented, but the shutdown process takes longer
Solution Approach 1:
The control unit changes the operational parameters by reducing the motor/generator unit speed according to a predetermined deceleration ramp. This controlled parameter change transitions the screw rotor from normal operating speed to a lowest speed range, balancing protection needs with shutdown efficiency.
3Ease of operation
If the motor/generator unit speed is controlled according to a deceleration ramp, then smooth transition to lowest speed is achieved, but control complexity increases
Solution Approach 1:
The control unit monitors the motor/generator unit speed and adjusts the deceleration process according to a predetermined deceleration ramp. This feedback mechanism ensures the screw rotor speed is reduced smoothly to the lowest speed range while maintaining manageable control complexity through automated speed regulation.
4Reliability
If the lowest speed range is maintained for a holding time, then pressure equalization is ensured, but operational time is extended
Solution Approach 1:
The control unit maintains the screw rotor in the lowest speed range for a predetermined holding time before complete shutdown. This preliminary action allows pressure differences between high-pressure and low-pressure sides to equalize, preventing damage upon restart while limiting the extension of operational time.
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 effectively prevents damage by reducing pressure differences and maintaining a lubricant film, ensuring the compressor/expander machine operates safely and efficiently by avoiding abrasion and overheating.
Implementation Method 1
reduces the speed of the motor/generator unit according to a predetermined speed profile until a lowest speed range of the at least one screw rotor is reached
Implementation Method 2
maintaining a lubricant film, ensuring the compressor/expander machine operates safely and efficiently by avoiding abrasion and overheating
Data Source
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AI summary
Compressor/expander machine and method for operating the same in a circuit for a working medium, wherein the compressor/expander machine has a machine housing with a screw rotor housing in which at least one screw rotor arranged between a low-pressure side and a high-pressure side is arranged for compressing/expanding the working medium and is coupled to a motor/generator unit, wherein an operating control unit is provided which, in the event of a termination of operation of the compressor/expander machine, operates the motor/generator unit according to a predetermined speed profile until a minimum speed range of the at least one screw rotor is reached, preventing damage in the area of the screw rotors.