Screw Compressor Rotor Axial Force Direction and Single Bearing
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Solution Overview
Problem
Existing screw compressor elements face challenges with axial bearing loads, temperature-induced length changes, and inefficient synchronization due to oblique toothing, leading to increased costs, mechanical losses, and reduced operational efficiency, particularly in dynamic transitional modes and varying temperature conditions.
Innovation Solution
The compressor element features a male rotor with a drive gearwheel and synchronisation gearwheels having specific toothing orientations to ensure consistent axial forces directed from the outlet to the inlet, reducing the need for additional prestress means and allowing a single axial bearing for the male rotor, while the female rotor uses dual axial bearings for stability, and both rotors are mounted with radial bearings to minimize mechanical losses and environmental exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If additional prestress means (springs or plungers) are added to the bearing cover to prevent rotor contact with housing, then rotor stability is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for additional prestress means (springs or plungers) by redesigning the axial bearing arrangement. The single axial bearing on the outlet side, combined with the drive gearwheel's axial force direction, sufficiently prevents rotor contact with the housing without requiring extra prestress components, thereby simplifying the bearing cover design.
Solution Approach 2:
Instead of adding prestress means to push the rotor away from the housing, the invention inverts the approach by using the drive gearwheel's axial force (naturally directed from inlet to outlet) to push the rotor toward the housing, where the single axial bearing on the outlet side then prevents contact. This reverses the conventional wisdom about prestress direction.
2Device complexity
If a single axial bearing is used for the male rotor, then device complexity is reduced, but reliability may worsen due to higher load concentration
Solution Approach 1:
The invention changes the parameter of axial force direction by designing the drive gearwheel with oblique toothing that generates axial force directed from the inlet to the outlet side. This parameter change allows the single axial bearing on the outlet side to effectively handle the combined axial loads (drive force + gas force), maintaining reliability while reducing complexity.
Solution Approach 2:
The single axial bearing on the outlet side acts as a counterweight mechanism, balancing the axial forces from the drive gearwheel and gas pressure. The bearing's position and loading characteristics compensate for the reduced number of bearings, maintaining system reliability through optimized force distribution.
3Stability of the object's composition
If oblique toothing is used in synchronisation gearwheels, then synchronization is achieved, but mechanical losses increase due to temperature-induced length changes
Solution Approach 1:
The invention changes the geometric parameter of the synchronisation gearwheels by using straight toothing instead of oblique toothing. This parameter change eliminates the mechanical losses associated with oblique toothing while maintaining synchronization functionality through the straight gear teeth, which are less sensitive to temperature-induced length changes.
4Force
If the drive gearwheel is positioned on the inlet side, then axial force direction is improved, but the axial bearing is exposed to more severe environmental conditions
Solution Approach 1:
The invention segments the bearing arrangement by placing the single axial bearing on the outlet side rather than the inlet side, separating the bearing from the severe environmental conditions on the inlet side while maintaining the beneficial axial force direction from the drive gearwheel. This spatial segmentation protects the bearing from environmental harm while preserving the force optimization.
Data Source
Figure 1
Figure 2
AI summary
Compressor element of a screw compressor (1) inlet side (9) and an outlet side (11) and two helical rotors (6 and 7), respectively a male rotor (6) with a drive for the male rotor (6) and a female rotor (7) that is driven by the male rotor (6) by means of synchronisation gearwheels (24 and 25) with at least one synchronisation gearwheel (24) on the male rotor (6), characterised in that the drive and synchronisation gearwheels (24) of the male rotor (6) are chosen such that, upon being driven with acceleration of the rotors (6 and 7) without gas forces, the resulting mechanical drive force that is exerted by this drive and by this synchronisation gearwheel (24) on the male rotor (6) has an axial component (Fp and Fs) that is directed from the outlet side (11) to the inlet side (9) and that the movement of the male rotor (6) in the axial direction (X-X') from the outlet side (11) to the inlet side (9) is fixed by means of a single axial single-acting or double-acting bearing (16).