Rotor Tie Rod Fixing Structure for Corrosion-Resistant High-Speed Operation
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Solution Overview
Problem
Rotors in wet saturated gas environments experience cracking and damage due to high centrifugal forces, especially when using high resistance steel, which is corroded by gases like H2 or H2S, leading to reduced rigidity and potential unpacking of the magnetic mass.
Innovation Solution
A rotor design with tie rods fixed in radial direction throughholes by conical nuts and counterbores, ensuring stability and preventing bending stresses, allowing the use of high resistance steel even at high speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high resistance steel is used for tie rods to withstand high centrifugal forces at high speeds, then the rotor can operate at high rotation speeds, but the steel is corroded by H2 or H2S gases in WSG environment leading to cracks and rotor damage
Solution Approach 1:
The patent replaces expensive high resistance steel tie rods with standard steel tie rods that are less susceptible to corrosion in WSG environments. While standard steel has lower mechanical strength, the design compensates through structural modifications (counterbores and fixing elements) to maintain adequate performance at high speeds while improving reliability in corrosive environments.
2Reliability
If standard steel is used for tie rods to avoid corrosion in WSG environment, then reliability in corrosive environment improves, but the tie rods cannot withstand high centrifugal forces at high rotation speeds
Solution Approach 1:
The tie rod assembly is segmented into multiple components: the tie rod itself, counterbores in the compaction elements, and fixing elements. This segmentation allows the use of standard steel for the tie rod while the fixing elements and counterbore geometry provide additional mechanical support to withstand high centrifugal forces at high rotation speeds.
Solution Approach 2:
The patent introduces a radial dimension constraint through the counterbore and fixing element arrangement. The fixing elements are positioned in counterbores that constrain the tie rods radially, adding a dimensional constraint that compensates for the lower strength of standard steel and enables high-speed operation.
3Reliability
If the section of tie rod is reduced at the end of thread to avoid cracks, then crack formation is reduced, but the tie rod strength is reduced making it more susceptible to bending and damage under high centrifugal forces
Solution Approach 1:
The patent compensates for the reduced tie rod strength (due to section reduction at the thread end) by introducing radial constraints through fixing elements in counterbores. This adds a dimensional constraint that prevents bending and distributes loads, allowing the weakened tie rod to still withstand high centrifugal forces.
Solution Approach 2:
The counterbores and fixing elements are pre-positioned in the compaction elements before operation. This preliminary structural arrangement ensures that radial constraints are already in place to support the tie rods, compensating for their reduced strength before high centrifugal forces are applied during high-speed rotation.
4Reliability
If compaction force is reduced to decrease constraints in tie rods, then standard steel can be used, but the magnetic mass may unpack reducing rotor rigidity at high rotation speeds
Solution Approach 1:
The patent maintains adequate compaction force on the magnetic mass while using standard steel tie rods by introducing radial constraints through fixing elements in counterbores. The radial constraint dimension compensates for the lower strength of standard steel, allowing sufficient compaction force to be applied without causing tie rod failure, thereby maintaining magnetic mass rigidity.
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
Prevents cracking and maintains rotor rigidity in wet saturated gas environments by stabilizing tie rods, enabling high-speed operation without compromising compaction force on the magnetic mass.
Implementation Method 1
each nut may be subjected to an acceleration greater than 10000 times the gravity so that the generated centrifugal force is greater than the friction forces maintaining each nut
Implementation Method 2
the nuts at the extremities of each tie rod are only maintained in an axial direction of the rotor on the free side of a half shaft by friction forces
Data Source
AI summary
The rotor for rotary electric machine has a magnetic mass clamped between two compaction elements, and tie rods passing through the magnetic mass and connecting the two compaction elements, at least a first compaction element has as many through holes as tie rods, each through hole of the first compaction element has a counterbore on one side opposite to the side in contact with the magnetic mass, each tie rod passing through a different through hole of the first compaction element and being fixed in the said through hole by a fixing element of the first compaction element logged in the counterbore, characterized in that each fixing element and the associated counterbore cooperate so that each fixing element is in contact with the counterbore in a radial direction of the rotor.