The shaft sleeve of the screw compressor rotor is the core component that supports the anode and cathode rotors, directly affecting the stability, efficiency, and lifespan of the equipment operation. Its working principle involves three core mechanisms: mechanical load-bearing, thermodynamic compensation, and friction control. The following analysis is conducted from the perspectives of structure, function, and failure protection:
1、 Structure and Mechanical Bearing Mechanism
The supporting positioning function shaft sleeve is fixed to the rotor shaft neck through interference fit or hydraulic expansion. The clearance between the inner hole and the shaft diameter is ≤ 0.02mm, ensuring that the radial runout of the rotor is less than 0.01mm and meeting the coaxiality requirements under high-speed rotation (3000-6000rpm).
Analogy: Similar to the main bearing of a car engine crankshaft, it needs to withstand the composite load generated by the rotor's own weight, gas pressure, and inertial force (the axial force of a single-stage screw machine can reach 10-50kN).
The load distribution optimization adopts a stepped shaft sleeve design: the shaft sleeve near the exhaust end bears higher pressure (due to the maximum gas compression ratio), and the anti deformation ability is improved by thickening the wall thickness (30% -50% thicker than the intake end).
Data example: A certain brand of 75kW screw machine has an exhaust end shaft sleeve hardness of HRC60, which is higher than the intake end (HRC55) to resist high-pressure wear.
2、 Thermodynamics compensation and gap control
The thermal expansion coefficient of the thermal expansion compensation shaft sleeve material (such as copper alloy/bimetallic composite layer) should be matched with the rotor shaft (Δα ≤ 2 × 10 ⁻⁶/℃) to avoid jamming or leakage caused by temperature differences (the temperature difference on the rotor surface under normal working conditions can reach 50-80 ℃).
Technical means: Adopting a wavy inner hole or elastic groove structure, absorbing thermal expansion difference through micro deformation (compensation amount can reach 0.05-0.1mm).
Reserve a radial gap of 0.03-0.08mm between the outer circle of the dynamic clearance adjustment shaft sleeve and the body hole, and use a floating sealing ring to achieve adaptive adjustment. When the rotor expands due to heat, the shaft sleeve can move slightly axially (≤ 0.2mm), maintaining a constant end face clearance and reducing internal leakage rate (<3%).
3、 Friction, Wear and Lubrication Protection
The mechanism of lubricant film formation is to machine spiral oil grooves on the surface of the shaft sleeve (groove depth 0.02-0.05mm, pitch synchronized with rotor lead), and form a fluid dynamic pressure lubricant film through forced oil supply, with a bearing capacity of 10-20MPa and a friction coefficient<0.02.
Comparison: When there is no oil film, the wear rate of the shaft sleeve reaches 0.1mm/thousand hours, and when lubrication is sufficient, the wear rate is less than 0.005mm/thousand hours.
Anti bite and wear-resistant design surface treatment: Laser cladding NiCrBSi alloy layer (thickness 0.2-0.3mm) is used, with a hardness of HV800-1000 and an anti bonding temperature increased to 400 ℃ (ordinary steel shaft sleeves are only 250 ℃).
Failure protection: The built-in temperature sensor monitors the surface temperature of the shaft sleeve. When it exceeds 120 ℃, an alarm is triggered and the backup oil pump is started to avoid tile burning accidents.
4、 Failure modes and maintenance strategies
Typical failure causes: Insufficient lubrication accounts for 60% of the failure rate, manifested as scratches on the surface of the shaft sleeve and peeling of Babbitt alloy.
Foreign object intrusion: Impurities in the refrigerant cause plowed wear on the surface of the shaft sleeve (depth>0.05mm needs to be replaced).
Maintenance suggestion: Regular inspection: Check the surface of the shaft sleeve with an endoscope every 2000 hours and measure the radial clearance (if it exceeds the tolerance by 0.1mm, it needs to be replaced).
Selection principle: Graphite self-lubricating shaft sleeves are preferred for high temperature conditions (>90 ℃), while stainless steel base shaft sleeves are required for chlorine containing refrigerants (such as R22).