Turbine Diaphragm Mechanical Interlocking
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Solution Overview
Problem
The construction of steam turbine diaphragms using traditional welding methods is costly and prone to metallurgical defects, with deep penetration welds requiring specialized equipment and inducing stress that necessitates heat treatment.
Innovation Solution
A novel diaphragm structure where blade units with integral inner and outer platforms are assembled using mechanical engagement features such as hooks and grooves, eliminating the need for welding and allowing for near-net shape construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional welding methods are used to join inner and outer rings to platforms, then structural strength and integrity are achieved, but manufacturing cost increases and metallurgical defects occur
Solution Approach 1:
The diaphragm is divided into modular blade units, each comprising an aerofoil portion with integrated inner and outer platforms. These segmented units are mechanically assembled rather than welded, eliminating the need for costly deep penetration welds while maintaining structural integrity through precise mechanical interlocking.
Solution Approach 2:
The inner and outer platforms are merged with the aerofoil portion to form integral blade units. This integration eliminates separate welding operations between platforms and rings, reducing manufacturing cost and avoiding weld-induced metallurgical defects while preserving the required structural strength.
2Strength
If deep penetration welds are used to join thick metal plate rings, then strong joints are achieved, but specialized welding equipment and heat treatment are required
Solution Approach 1:
The welding process is replaced with a mechanical assembly system. Blade units are joined through precise mechanical interlocking of engagement features between adjacent units, eliminating the need for specialized deep penetration welding equipment and subsequent heat treatment facilities while achieving equivalent joint strength.
3Reliability
If welds are used to assemble diaphragm components, then components are joined securely, but metallurgical defects and residual stresses occur
Solution Approach 1:
The harmful welding process is extracted and removed from the assembly process. Instead of joining components through welding, the invention uses mechanical engagement features that securely assemble blade units without introducing metallurgical defects or residual stresses, thereby maintaining joint reliability while eliminating harmful byproducts.
4Strength
If solid inner and outer rings are used in platform construction, then structural support is provided, but welding costs increase significantly
Solution Approach 1:
The solid inner and outer rings are segmented into modular blade units with integrated platforms. This segmentation allows mechanical assembly through engagement features, eliminating the need for expensive welding operations while maintaining the structural support function of the rings.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3C
AI summary
An axial flow turbine diaphragm (10) is constructed without welding or other metal joining techniques as an annular array of static blade units (12). Each blade unit (12) comprises an aerofoil (18) and radially inner and outer platforms integral with the aerofoil. The radially inner platform consists of a segment (14) of the inner diaphragm ring and the radially outer platform consists of a segment (16) of the outer diaphragm ring. At least the outer ring segment (16) has engagement features (161, 162, 165, 166) that mechanically engage with complementary engagement features on neighbouring outer ring segments in the annular array of blade units, the engagement features acting to mechanically interlock neighbouring outer ring segments and produce a self-supporting turbine diaphragm.