Multistage Rotor Shaft Assembly to Prevent Tie-Bolt Imbalance
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Solution Overview
Problem
The multistage rotor in existing turbo machines experiences imbalance due to misalignment between rotor shafts and tie bolts, which can lead to increased interference with natural frequencies and reduced compression efficiency.
Innovation Solution
A multistage rotor design featuring a single rotor shaft with stepped surfaces and lock nuts that pressurize impellers between the stepped surfaces, eliminating the need for tie bolts and ensuring precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of stages and rotation peripheral speed are increased to achieve higher compression rate, then the rotor axial length must be increased, but this increases the risk of interference between natural frequency of the tie bolt and operation rotational frequency
Solution Approach 1:
The patent removes the tie bolt from the system entirely and replaces it with a single integrated rotor shaft design. The impellers are directly mounted on the rotor shaft with lock nuts, eliminating the intermediate component that caused frequency interference issues. This extraction of the problematic tie bolt element resolves the frequency interference risk while maintaining the ability to achieve high compression rates through increased stage count and peripheral speed.
2Reliability
If the tie bolt diameter is increased to detune natural frequency from operation rotational frequency, then the influence of misalignment between rotor shaft and tie bolt on imbalance increases
Solution Approach 1:
The patent merges the rotor shaft and impeller assembly into a more integrated structure where impellers are directly mounted on the rotor shaft using lock nuts. This eliminates the separate tie bolt component and its associated misalignment issues. The direct mounting approach ensures precise alignment between the rotation axis and impeller centers, reducing imbalance while maintaining frequency detuning through proper shaft design.
3Ease of manufacture
If a tie bolt structure is used to connect impellers, then assembly is simplified, but misalignment between rotor shaft and tie bolt causes imbalance that is difficult to remove
Solution Approach 1:
The patent extracts the tie bolt from the assembly structure and replaces it with direct mounting of impellers on the rotor shaft using lock nuts. This eliminates the intermediate connection component that caused misalignment and imbalance issues. The direct mounting approach maintains assembly simplicity while significantly improving alignment precision and reducing imbalance.
Data Source
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AI summary
A turbo machine includes a casing and a multistage rotor supported by the casing. The multistage rotor includes: a rotor shaft that is a single object and includes a stepped surface; impellers fitted to the rotor shaft and lined up in an axial direction of the rotor shaft from the stepped surface; and a lock nut fitted to the rotor shaft. The impellers are sandwiched between the stepped surface and the lock nut.