Segmented Francis Runner Welding Outside High-Stress Blade Junctions
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Solution Overview
Problem
The manufacturing and transportation of large Francis-type turbine runners for hydroelectric power stations are costly and pose health and safety risks due to the need for complex welding and grinding operations, and existing segment-based solutions often require joints at high-stress areas, compromising strength and safety.
Innovation Solution
A Francis-type runner is formed from identical segments with integrally formed band, crown, and blade portions, where the blade is positioned away from joining edges, allowing for welding outside the runner and using narrow gap welding techniques to avoid high-stress areas, enabling efficient and safe assembly with robotic tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the runner is made as a single large cast or welded piece, then the structural strength and integrity are improved, but the manufacturing cost increases, transportation becomes difficult, and specialized skills are required
Solution Approach 1:
The runner is divided into multiple segments that can be manufactured separately and assembled together. Each segment contains a portion of the blades and is cast independently, allowing for easier manufacturing and transportation while maintaining structural integrity through proper joining methods
2Ease of manufacture
If the runner is split into segments and welded together, then transportation and manufacturing become easier, but welding joints must be formed at high-stress areas such as blade-crown and blade-band junctions, compromising strength and safety
Solution Approach 1:
The runner is segmented in a way that allows joints to be positioned away from high-stress blade attachment areas. The segmentation strategy places joints in lower-stress regions of the crown and band, preserving structural integrity while enabling modular construction
Solution Approach 2:
The segment design extends the blade attachment areas in the axial direction away from the radial joints. By positioning blade roots at different axial locations than the crown-band joints, the high-stress blade attachment zones are separated from the welding joint zones, allowing joints to be formed in lower-stress areas
3Ease of manufacture
If welding and grinding operations are performed inside hydraulic passages of the runner, then assembly is possible, but health and safety risks increase due to confined space operations
Solution Approach 1:
Instead of performing welding operations from the inside of the hydraulic passages, the segment design allows all welding joints to be accessed and performed from the outside of the runner. The joints are positioned on external surfaces of the crown and band, eliminating the need for workers to enter confined hydraulic passages for welding and grinding operations
4Power
If the runner is made in large dimensions for hydroelectric power stations, then the power generation capacity increases, but the manufacturing cost increases and transportation becomes difficult
Solution Approach 1:
The large-scale runner is divided into smaller segments that can be manufactured more cost-effectively and transported more easily. The segmentation allows each component to be optimized for its specific manufacturing constraints while assembling to form the complete large-diameter runner required for high-power hydroelectric applications
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
This approach reduces manufacturing costs, enhances safety by avoiding health risks, and strengthens the joints by placing welds away from high-stress areas, resulting in a more efficient and safer assembly process for large hydraulic machine runners.
Implementation Method 1
the segments are joined together by welding
Data Source
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AI summary
A runner (4) for a hydraulic machine comprising a band (20), a crown (22), a plurality of blades (24) extending between the crown (22) and the band (20), wherein the runner (4) comprises a plurality of runner segments (30) which together define the runner (4), each runner segment (30) comprising a band portion (34), a crown portion (32) and a blade (24), which portions are integrally formed with one another, each runner segment (30) being attachable to another segment at a band joining edge and a crown joining edge, wherein the band joining edge and the crown joining edge are each spaced apart from the blade (24) of the segment.