Wear Ring Thermal Decoupling in Flow Machines
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Solution Overview
Problem
Radial sealing gaps in flow machines can widen undesirably due to thermal expansion differences between the rotor and wear rings, leading to wear and potential damage during start-up transients, especially when handling hot fluids.
Innovation Solution
A flow machine design featuring a wear ring with an elastically deformable fastening part, which creates radial gaps between the wear ring and the fastening part, and between the fastening part and the stator, allowing the wear ring to move radially and thermally decouple from the stator, using materials like nitride-hardened cast steel or ceramics with low thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wear ring is used in the sealing gap, then wear resistance is improved, but thermal expansion differences cause the sealing gap to shrink during start-up transients
Solution Approach 1:
The wear ring is segmented into two parts: the wear ring itself and the elastically deformable fastening part. This segmentation allows the wear ring to be thermally decoupled from the stator, enabling independent thermal expansion behavior that prevents sealing gap shrinkage during transient operations.
Solution Approach 2:
The fastening part is designed with elastic deformability, allowing it to change its mechanical properties (stiffness) in response to thermal expansion differences. This parameter change enables the fastening part to accommodate radial movements of the wear ring during thermal transients, preventing harmful gap shrinkage.
2Ease of manufacture
If the wear ring is rigidly fixed to the stator, then manufacturing simplicity is improved, but thermal expansion causes sealing gap distortion
Solution Approach 1:
The fastening connection is designed to be dynamically adaptable rather than rigid. The elastically deformable fastening part can adjust its stiffness and positioning in response to thermal conditions, maintaining manufacturing simplicity while preserving sealing gap precision during thermal transients.
3Loss of energy
If the sealing gap is made narrow to reduce flow losses, then energy efficiency is improved, but wear and damage risk increase during thermal transients
Solution Approach 1:
The elastically deformable fastening part acts as a cushioning element that anticipates and compensates for thermal expansion differences before they can cause harmful effects. This prior cushioning prevents sealing gap shrinkage and potential damage during thermal start-up transients, allowing the use of narrow sealing gaps for energy efficiency.
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
The design enables the wear ring to adapt to temperature changes, preventing the sealing gap from shrinking below permissible sizes during start-up transients, thus preventing damage and ensuring reliable operation of flow machines for hot fluids.
Implementation Method 1
the wear ring is fastened to a stator part via an elastically deformable fastening part
Implementation Method 2
the material of the wear ring 5 has a heat expansion coefficient α of less than 10×10−6/° C.
Data Source
AI summary
A flow machine for a fluid is presented with a radial sealing gap (9) between stator parts (4) and a rotor (3), wherein at least one wear ring (5) is provided at the sealing gap and is fastened to a stator part (4) via an elastically deformable fastening part. The fastening part (6) is connected on the one side to the stator part (4). On this side a radial gap (8) is formed between an outer jacket surface of the wear ring and the fastening part and, on the other side, with the wear ring. On this side a radial gap (7) is formed between an outer jacket surface of the fastening part and the stator part.