Segmented Bling Assembly for Steam Turbine Tolerance Control
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Solution Overview
Problem
Steam turbines face challenges due to cumulative dimensional deviations in component assembly, leading to increased manufacturing costs and reduced efficiency, and pre-twist airfoils can be difficult to maintain with stringent process control, affecting stress absorption and alignment.
Innovation Solution
A bling assembly is formed by coupling two semi-circular members with mating surfaces to create a circular ring, featuring concentric airfoil portions and seal carrier extensions, which are machined to reduce dimensional tolerances and facilitate steam flow management through precise machining techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual component tolerances are decreased to mitigate stack-up tolerances, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The bling assembly is divided into multiple discrete airfoil segments that can be manufactured separately with standard tolerances and then assembled together. This segmentation allows each component to be produced using conventional manufacturing processes without requiring ultra-precise tolerances, thereby reducing manufacturing cost while maintaining overall assembly precision through proper alignment features during assembly.
Solution Approach 2:
Multiple airfoil segments are combined into a single assembled bling assembly structure. By merging these segments through precise alignment and coupling mechanisms, the assembly achieves the functional equivalent of a monolithic structure with tight tolerances, while individual components maintain more relaxed manufacturing tolerances, thus reducing overall manufacturing cost.
2Reliability
If pre-twist airfoils are used to absorb dynamic stresses, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
Instead of relying on precise pre-twist angles that are difficult to control during manufacturing, the design incorporates airfoil segments with adjustable or variable geometric parameters. This allows the airfoils to adapt to operational stress patterns without requiring stringent pre-manufacturing precision, thereby maintaining reliability while reducing manufacturing precision requirements.
Solution Approach 2:
The airfoil segments are designed with features that allow them to dynamically adjust their orientation and stress distribution during operation rather than relying on fixed pre-twist angles. This dynamic capability enables the airfoils to absorb varying dynamic stresses effectively, improving reliability without the need for extremely precise pre-manufacturing tolerances.
3Ease of manufacture
If cumulative dimensional deviations are allowed in assembly, then ease of manufacture is improved, but steam turbine efficiency decreases
Solution Approach 1:
Alignment features and coupling mechanisms serve as intermediary elements between airfoil segments. These intermediaries compensate for dimensional deviations by providing adjustment capabilities, ensuring that even with relaxed individual component tolerances, the assembled bling assembly maintains proper steam flow paths and operational efficiency.
Solution Approach 2:
The design incorporates features that address dimensional deviations in additional dimensions beyond simple linear tolerances. By managing deviations in multiple spatial dimensions simultaneously through sophisticated alignment features, the assembly maintains steam flow efficiency even when individual components have broader tolerance ranges.
Data Source
AI summary
A rotary machine includes a rotor, a stationary machine casing extending around the rotor, and a bling assembly extending between the casing and the rotor. The machine also includes at least one rotor tip seal assembly and at least one shaft seal assembly. The seal assemblies have a groove configured to receive at least one seal ring band. A method of assembling a rotary machine is also provided. The method includes fabricating the bling assembly by providing two identical members comprising a mating surface and having a semi-circular profile. The method also includes coupling the two members together at their mating surfaces such that a circular ring is formed and such that the mating surfaces define a horizontal joint. The method further includes machining concentric, circular and annular radially inner and outer and airfoil portions within predetermined radial portions of the bling assembly. The method also includes forming at least one abradable layer over a plurality of seal ring bands and inserting the plurality of seal ring bands into the rotor tip and shaft seal ring grooves.