Impeller Clamping Assembly for Centrifugal Compressor Shaft Deflection
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Solution Overview
Problem
In multi-stage centrifugal compressors, impeller deformation due to thrust loads causes operational vibration and noise, and the tolerance stack-up effect leads to rotating imbalances, which existing technologies fail to adequately address.
Innovation Solution
A clamping assembly is used that includes a relatively stiff support for the front side of the impeller to relieve deflection and a relatively flexible support for the backside to compensate for thermal expansion, comprising a locknut and a spring member, such as a Belleville washer, to independently support each impeller and reduce shaft deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If impellers are mounted on a shaft without individual clamping, then the structure is simpler, but impeller deformation due to thrust loads causes operational vibration and noise
Solution Approach 1:
The patent divides the support function into separate clamping assemblies for each impeller, with individual stiff and flexible supports for each impeller backside, rather than a single collective support structure. This segmentation allows each impeller to be independently supported, reducing vibration and noise while maintaining manageable complexity.
Solution Approach 2:
The patent applies different support characteristics at different locations: a relatively stiff support structure for the front side of each impeller to resist thrust loads, and a relatively flexible support structure for the backside to accommodate thermal expansion and reduce deformation. This local differentiation of support rigidity addresses the vibration problem effectively.
2Ease of manufacture
If impellers are mounted without clamping, then the assembly is easier, but tolerance stack-up effect leads to rotating imbalances
Solution Approach 1:
The clamping assemblies are pre-installed on the shaft before impeller mounting, establishing fixed reference positions. This preliminary action eliminates the need for complex post-assembly adjustments and ensures precise positioning of each impeller, thereby reducing tolerance stack-up effects and improving rotating balance.
Solution Approach 2:
The clamping assemblies act as intermediary components between the shaft and impellers, providing precise positioning and alignment. These intermediaries compensate for manufacturing tolerances in both the shaft and impellers, ensuring accurate relative positioning without requiring extremely tight manufacturing tolerances on the impellers themselves.
3Stability of the object's composition
If a stiff support is used for the front side of the impeller, then deflection is reduced, but thermal expansion compensation is limited
Solution Approach 1:
The patent applies different support rigidity characteristics at different locations: a relatively stiff support structure for the front side of each impeller to resist thrust loads and reduce deflection, and a relatively flexible support structure for the backside to accommodate thermal expansion. This local differentiation resolves the contradiction between stability and adaptability.
Solution Approach 2:
The support system transitions from a static, uniformly rigid structure to a dynamic system with differentiated rigidity characteristics. The flexible backside support allows the impeller to dynamically adjust to thermal expansion while the stiff front support maintains operational stability during compression cycles.
4Device complexity
If multiple impellers are assembled without individual clamping, then the device is simpler, but shaft deflection increases
Solution Approach 1:
Instead of a single collective support structure, the patent segments the support function into multiple independent clamping assemblies, each with its own stiff and flexible support components. This segmentation allows each impeller to be independently supported, preventing load accumulation that would cause shaft deflection while keeping each individual clamping assembly relatively simple.
Solution Approach 2:
The patent applies support action at multiple discrete locations along the shaft rather than relying on a single support point. By distributing the support action across multiple clamping assemblies positioned at different locations, the system provides sufficient total support to prevent shaft deflection without requiring any single support component to be overly complex.
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 solution reduces the tolerance stack-up effect and vibration by distributing the thrust load effectively, allowing for a tighter interference fit and improved stability of the impellers, thereby minimizing shaft deflection and operational noise.
Implementation Method 1
the relatively flexible support may include a spring member configured to provide a relatively flexible support to the backside of the impeller, which can help compensate for, e.g., thermal expansion/contraction of the impeller
Implementation Method 2
the spring member may include a conical washer such as, but not limited to, a Belleville washer
Implementation Method 3
the relatively flexible support may include a spring member configured to provide a relatively flexible support to the backside of the impeller
Data Source
AI summary
Systems and methods to clamp an impeller on a shaft in a centrifugal compressor. The embodiments as disclosed herein may include clamping individual impeller independently to the shaft, which may reduce the tolerance stack-up effect of a plurality of impellers. The impeller can be clamped to the shaft by positioning, for example, a relatively stiff support (e.g. a shaft locknut) on a front side of the impeller. The impeller can also be clamped to the shaft by a relatively flexible support to compensate for e.g. thermal expansion/contraction of the impeller. The embodiments as disclosed herein are particularly suitable for a multi-stage impeller.