Magnetic Axial Force Compensation in Screw Compressors
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Solution Overview
Problem
Screw compressor elements face challenges in accommodating reversing axial forces during startup and nominal operation, leading to inefficiencies, leakage losses, and increased costs due to complex and expensive solutions like dual-action axial bearings and balancing pistons.
Innovation Solution
A method using magnetic forces to compensate axial forces on the rotor, with magnets switched on or off depending on the operational mode, allowing for optimized bearing load and reduced mechanical losses, enabling the use of smaller and less complex bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual-action axial bearings are used to accommodate reversing axial forces, then the rotor can be immobilized in both directions, but the device complexity and cost increase significantly
Solution Approach 1:
The patent replaces the mechanical dual-action axial bearing system with a magnetic field-based active control system. Electromagnets mounted on the housing generate controllable magnetic forces that act on ferromagnetic components of the rotor, enabling axial force compensation without complex mechanical bearings. This substitution reduces mechanical complexity while maintaining rotor immobilization capability.
Solution Approach 2:
The patent implements dynamic control of axial forces by adjusting the excitation currents of the electromagnets based on operating conditions. During startup, magnetic forces compensate for gearwheel axial forces; during nominal operation, they compensate for gas forces. This dynamic adaptation allows a simpler bearing structure to handle varying axial load requirements effectively.
2Reliability
If dual-action axial bearings with inherent axial play are used, then forces can be accommodated in both directions, but the rotor moves over a distance equal to the play, requiring larger head clearance and causing leakage losses
Solution Approach 1:
The patent eliminates the inherent axial play of mechanical bearings by replacing it with a magnetic control system. The electromagnets continuously adjust magnetic forces to maintain optimal rotor position, preventing the rotor from moving through the axial play distance. This maintains small head clearance and prevents gas leakage losses while still accommodating reversing axial forces.
3Reliability
If dual-action axial bearings are used to prevent rotor contact with housing, then friction and wear are avoided, but mechanical losses and churning losses from lubricant increase
Solution Approach 1:
The patent replaces the lubricant-dependent mechanical bearing system with a magnetic field-based control system. The electromagnets generate the necessary axial forces without requiring lubricants, completely eliminating churning losses associated with lubricant circulation. The rotor remains properly positioned without contact with the housing, preventing wear while avoiding the energy penalties of mechanical lubrication systems.
4Loss of energy
If a balancing piston is used to counteract gas forces, then the main bearing load is reduced, but the cost and device complexity increase
Solution Approach 1:
The patent replaces the hydraulic/pneumatic balancing piston system with an electromagnetic force generation system. Electromagnets mounted on the housing directly generate the compensating axial forces needed to counteract gas forces acting on the rotor. This eliminates the need for balancing pistons, their chambers, and associated fluid systems, reducing both cost and complexity while achieving the same bearing load reduction effect.
5Device complexity
If a spring is used to prevent force reversal on the main bearing, then a single-action bearing can be used, but the spring increases load on the bearing during nominal operation
Solution Approach 1:
The patent implements dynamic control of magnetic forces to adapt to changing operating conditions. During startup, magnetic forces prevent force reversal on the bearing. During nominal operation, the magnetic forces are adjusted to compensate for gas forces rather than opposing them, unlike a spring which would continuously increase bearing load. This dynamic adaptation allows use of simpler single-action bearings without the penalty of increased nominal operating loads.
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 method effectively compensates axial forces, reducing the need for costly compensating measures, minimizing mechanical losses, and allowing operation under various conditions, including high speeds, with reduced lubrication needs and lower costs.
Implementation Method 1
the effect of which can act in the axial direction on at least one rotor (3, 4) of the compressor element
Data Source
AI summary
Method for controlling a compressor element of a screw compressor, where the compressor element has a housing with two meshing helical rotors supported in the housing in the axial direction using at least one axial bearing. The method has a process A and/or a process B, where process A has a first step of switching on a first magnet during start-up of the compressor element, such that the magnet exerts a force on the rotor that is directed from an outlet side to an inlet side, and of switching off this first magnet during nominal operation of the compressor element; and where process B has a first step of keeping a second magnet switched off during start-up of the compressor element, and switching on this second magnet during nominal operation of the compressor element, such that this second magnet exerts a force that is directed from the inlet side to the outlet side.