Force-Balanced Screw Compressor-Expander for High Pressure Differentials
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing screw compressors and expanders face challenges in handling large pressure differentials (>20 bar) due to high mechanical loads and complex designs, particularly when using supercritical carbon dioxide as a refrigerant, leading to significant wear and inefficiencies.
Innovation Solution
The design of a screw expressor with a screw compressor and expander on a common shaft, featuring rotors with identical cross-sectional areas twisted in opposite directions, allowing for internal force balancing and reduced mechanical contact, eliminating the need for precise gap adjustments and minimizing throttling losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional screw compressors are used to handle large pressure differentials (>20 bar), then the compression function is achieved, but high mechanical loads and complex designs result in significant wear and inefficiencies
Solution Approach 1:
The patent combines a screw compressor and screw expander into a single integrated unit with common shafts, allowing the expander to recover energy from the pressure differential while the compressor performs compression. This merging reduces overall mechanical stress on individual components and improves reliability by distributing loads across both machines.
Solution Approach 2:
The screw expander acts as a counterbalancing element to the screw compressor. The expander generates torque in the opposite direction, compensating for the high mechanical loads and axial forces experienced by the compressor during large pressure differential operation, thereby reducing wear and improving reliability.
2Device complexity
If an expander and compressor are positioned on common shafts to reduce components, then the number of bearings and seals is reduced, but large pressure differentials create high forces that are problematic
Solution Approach 1:
The expander serves as a counterbalancing machine that generates forces opposite to those produced by the compressor. By positioning both machines on common shafts, the axial and radial forces from the expander compensate for those from the compressor, reducing the net mechanical loads on bearings and seals while maintaining component simplicity.
Solution Approach 2:
The patent employs asymmetrical rotor profiles in both the compressor and expander, optimized for their respective functions. The compressor rotors are designed for efficient compression while the expander rotors are optimized for energy recovery, allowing each machine to handle its specific force characteristics while working together on common shafts.
3Productivity
If screw compressors with asymmetrical profiles are used, then compression efficiency is improved, but the high-pressure-side end gap must be adjusted to be as small as possible, increasing manufacturing complexity
Solution Approach 1:
By integrating the expander with the compressor on common shafts, the system creates a balanced force environment that reduces the criticality of precise end gap adjustments. The expander's opposing forces compensate for pressure imbalances, allowing for more practical manufacturing tolerances while maintaining compression efficiency through the asymmetrical rotor profiles.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a screw extruder (1) comprising a screw compressor (8) and a screw expander (9), wherein both the screw compressor (8) and the screw expander (9) each have a main rotor (18, 20) and a secondary rotor (19, 21) each with a helical toothing (4, 5, 6, 7) cooperating with the respective other rotor, and wherein the main rotors (18, 20) and the secondary rotors (19, 21) of the screw compressor (8) and screw expander (9) are each arranged on a common shaft (2, 3), wherein the screw compressor (8) is designed as a screw spindle compressor (8) and the screw expander (9) as a screw spindle expander (9), the main rotors (18, 20) and secondary rotors (19, 21) of which are designed for both the screw compressor (8) and the screw expander (9). for the screw expander (9) each have the same profile cross-section, but are twisted in opposite directions to each other,the twisting creates a chamber closure between the high-pressure side (12, 13) and the low-pressure side (11, 14) of the screw spindle compressor (8) and screw spindle expander (9), respectively.