Screw Compressor Balance Piston Thrust Cancellation
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Solution Overview
Problem
Screw compressors face shortened thrust bearing life due to increased discharge pressure, which existing balance piston technologies fail to adequately address, especially when capacity adjustments change the thrust force caused by gas reaction forces.
Innovation Solution
A screw compressor unit with a balance piston and a control device that adjusts fluid pressure on the piston based on compressor capacity, using a slide valve and pressure detectors to cancel thrust forces generated by the balance piston and gas reaction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the discharge pressure of the screw compressor increases, then the compression performance is improved, but the thrust force on the rotor shaft increases resulting in shortened thrust bearing life
Solution Approach 1:
The patent applies a balance piston to generate a counteracting thrust force that opposes the reaction force from compressed gas. The balance piston is pressed by fluid pressure from a hydraulic pump, creating a balancing force that cancels the harmful thrust force on the rotor shaft, thereby protecting the thrust bearing while maintaining high discharge pressure operation
2Productivity
If the capacity of the screw compressor is adjusted by changing the rotor chamber opening position, then the gas compression amount is adjusted, but the thrust force caused by gas reaction force changes even when suction and discharge pressures remain constant
Solution Approach 1:
The patent employs a control valve whose opening is adjusted according to the capacity setting of the screw compressor. This feedback mechanism ensures that as the capacity (gas compression amount) is adjusted via slide valve position, the control valve automatically modifies the fluid pressure applied to the balance piston, maintaining appropriate thrust force cancellation across all operating conditions
Solution Approach 2:
The system dynamically changes the fluid pressure parameter applied to the balance piston based on the compressor capacity setting. By adjusting the pressure of the fluid from the hydraulic pump through a control valve, the system adapts the balancing thrust force to match varying operational requirements, ensuring optimal thrust cancellation at each capacity level
3Adaptability or versatility
If a control valve is added to adjust fluid pressure on the balance piston according to suction/discharge pressures, then the thrust force adjustment capability is improved, but the device complexity increases
Solution Approach 1:
The control valve serves multiple functions: it adjusts fluid pressure to the balance piston for thrust force cancellation, and its opening is automatically adjusted based on capacity settings that account for suction and discharge pressures. This multi-functional approach provides comprehensive thrust adjustment capability while integrating the control mechanism into the existing capacity adjustment system, minimizing additional complexity
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
Effectively cancels thrust forces, extending the life of thrust bearings by dynamically adjusting fluid pressure on the balance piston in response to changes in compressor capacity and gas pressures.
Implementation Method 1
a balance piston for pressing a rotor shaft acting as a rotating shaft of at least one of the screw rotors in an axial direction by a fluid pressure
Data Source
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AI summary
In a capacity-adjustable screw compressor unit (1), a thrust force caused by a reaction force of gas can be appropriately cancelled by a balance piston (14). A screw compressor unit (1) of the present invention includes a compressor, having a pair of male and female screw rotors (4) meshing with each other contained in a casing (2), for compressing sucked gas and discharging it, a balance piston (14) for pressing a rotor shaft (9) acting as a rotating shaft of at least one of the screw rotors (4) in an axial direction by a fluid pressure, a slide valve (8) for adjusting capacity of the compressor (1), and a balance piston control device (22) for adjusting pressure of a fluid applied on the balance piston (14) according to the capacity of the compressor calculated from a position of the slide valve (8).