Screw Compressor Rotor Pre-tensioned Assembly
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Solution Overview
Problem
Single-piece rotors for screw compressors face challenges such as material wastage, difficulty in achieving optimal material properties for different parts, limited cooling efficiency, and repairability due to their monolithic design, which affects performance and efficiency.
Innovation Solution
A composite rotor design where the rotor body and shaft are manufactured separately, with the rotor body retained on the shaft via tension elements pre-tensioned to at least 30% of the yield strength, allowing for different materials to be used for different parts and facilitating easier assembly and repair, and incorporating a central cooling channel for enhanced cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-piece rotor is manufactured, then the rotor structure is simple and strong, but material is lost during production and different material properties cannot be optimized for different parts
Solution Approach 1:
The rotor is divided into separate components (rotor body and journals) that can be manufactured independently and then assembled together. This segmentation allows each part to be optimized for its specific requirements while reducing material wastage compared to manufacturing a complete single-piece rotor.
Solution Approach 2:
Different parts of the rotor can be manufactured from different materials optimized for their specific functions. The rotor body and journals can use different material compositions to achieve optimal properties for each component while maintaining overall structural integrity through the assembly process.
2Ease of manufacture
If the entire rotor is manufactured from the same material, then manufacturing is simplified, but optimal material properties for different parts (especially journals requiring robust bearing) cannot be achieved
Solution Approach 1:
By segmenting the rotor into separate components, the journals can be manufactured from materials specifically optimized for bearing reliability, while the rotor body can use different material properties suited for its function, eliminating the constraint of using a single material for the entire rotor.
Solution Approach 2:
Different materials with optimized properties can be applied to different parts of the rotor based on their specific functional requirements. The journals receive materials optimized for bearing reliability, while other parts can use materials optimized for their specific functions, achieving local quality optimization.
3Device complexity
If a single-piece rotor is used, then assembly is simple, but cooling efficiency is limited and repairability is difficult when only a single part is damaged
Solution Approach 1:
The rotor is segmented into separable components that can be independently manufactured and assembled. This segmentation enables easier repairability, as damaged components can be replaced without replacing the entire rotor, while the assembly process remains straightforward through standardized interfaces and retention mechanisms.
4Strength
If a single-piece rotor is manufactured, then structural integrity is maintained, but it is difficult to provide suitable cooling channels without substantially weakening the structure
Solution Approach 1:
By segmenting the rotor design, cooling channels can be integrated into specific components without compromising overall structural integrity. The separation allows for optimized cooling channel placement and sizing in individual parts while maintaining the strength requirements of the complete assembly.
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 design reduces material wastage, allows for optimal material selection for each part, improves cooling efficiency, and enables easier maintenance and repair, enhancing the overall performance and efficiency of the screw compressor.
Implementation Method 1
the stretch element which, during the assembly of the rotor body on the shaft, is pre-tensioned by means of tensile load and after locking said tension elements and removing the tensile load, is kept under an axial pre-tension
Implementation Method 2
A fraction of this heat is discharged through the rotor by means of convection
Data Source
AI summary
Rotor for a screw compressor includes a rotor body (2) and a shaft (6), whereby said shaft extends at least with a part into or through a central or approximately central axial bored hole or passage (5) in the rotor body (2). The shaft (6) has a stretch element (7), whereby the rotor body (2) or at least a part thereof is held on the shaft (6) by means of tension elements (11 and 12) which are locked or can be locked axially with respect to the shaft and which are connected with each other by means of the stretch element (7). During the mounting of the rotor body (2) on the shaft (6), the stretch element is pre-tensioned by means of a tensile load and after locking the tension elements (11 and 12) and removal of the tensile load, is kept under an axial pretension which, in case the rotor (1) is not built in, amounts to at least thirty percent of the yield strength of the material of the stretch element (7), and this by means of the tension elements (11 and 12) which are kept apart from each other by the rotor body (2) or a part thereof.