Multi-piece Locking Blade for Steam Turbine Rotor
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Solution Overview
Problem
Existing turbine rotor and blade assemblies in steam turbines face significant stress concentrations due to centrifugal and thermal loads, particularly at the areas where blade retention screws are inserted into the rotor, which can adversely impact rotor fatigue life.
Innovation Solution
A multi-piece locking blade configuration is introduced, featuring a base with planar sides and hooks with flanges that mate with a dovetail slot and groove in the rotor, eliminating the need for screws to be tapped into the rotor by using hooks within the locking blade groove for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If blade retention screws are inserted into the rotor to secure the locking blade, then the locking blade can be firmly attached to the rotor, but stress concentrations occur at the screw insertion points which adversely impact rotor fatigue life
Solution Approach 1:
The locking blade is divided into multiple segments: a blade portion, a base portion with hooks, and flange portions. This segmentation allows the load to be distributed across multiple attachment points (multiple hooks engaging with the rotor groove) rather than concentrating stress at single screw insertion points, thereby maintaining attachment strength while reducing stress concentrations that harm fatigue life
Solution Approach 2:
The invention extracts and eliminates the blade retention screws from the rotor structure. Instead of inserting screws into the rotor to secure the locking blade, the design uses hooks on the locking blade that engage with a groove in the rotor. This removal of intrusive fasteners eliminates the stress concentrations and potential fatigue initiation sites at screw hole locations, directly improving rotor fatigue life while maintaining secure attachment through the hook-groove mechanism
2Device complexity
If a single-piece locking blade is used with screw retention, then the structure is simple, but stress concentrations at screw insertion points reduce overall component reliability
Solution Approach 1:
The locking blade is segmented into a blade portion, base portion with hooks, and flange portions that can be manufactured separately and then assembled. This segmentation enables the use of a groove-based retention system instead of screw insertion, eliminating stress concentrations in the rotor while maintaining reasonable structural complexity through modular assembly
Solution Approach 2:
The design extracts the retention mechanism from the rotor material (eliminating screw holes) and relocates it to the locking blade itself (hooks engaging with groove). This extraction improves reliability by removing stress concentration sources from the rotor while the segmented structure manages complexity through modular design
Data Source
Figure 1~2
Figure 3~4
AI summary
Turbine rotor 120 and blade assembly 110 for a steam turbine 10. The turbine rotor 120 and blade assembly 110 may include a rotor, a number of buckets 140 positioned about the rotor, and a locking blade 170 positioned about the rotor. The locking blade 170 may include a multi-piece configuration 175. Correspondin multi-piece locking blade (170) for use with such a turbine rotor (120).