Hydraulic Turbine Hub Gap Adjustment Mechanism
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Solution Overview
Problem
Hydraulic turbine installations with gaps between blades and the hub face issues such as cavitation, pressure fluctuations, and reduced efficiency, which also pose risks to fish due to the gap size variability.
Innovation Solution
A hub design with adjustable raised or hollow areas near the blade edges, allowing for regulation of the gap extent through mechanisms like ejection/withdraw or rotational adjustments, optimizing the velocity field and efficiency by varying the gap size based on blade angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gap between the blade and hub is minimized or eliminated by inserting raised areas, then fish safety is improved and cavitation is reduced, but turbine efficiency deteriorates due to increased draft tube head loss
Solution Approach 1:
The patent applies the dynamics principle by making the raised area movable relative to the hub through adjustment means. The raised area can be positioned at different radial distances from the hub center, allowing the gap size to be dynamically changed based on operational requirements. This enables the system to adapt between fish safety mode (smaller gap) and efficiency mode (larger gap) as needed.
Solution Approach 2:
The patent implements parameter changes by varying the radial position of the raised area, which directly changes the gap parameter between the blade inner edge and the hub. By adjusting the raised area's position along the radial direction, the system can optimize the gap size to balance between preventing cavitation/fish safety and minimizing draft tube head loss for maximum efficiency.
2Productivity
If the gap extent is made variable through adjustment means, then turbine efficiency is improved by optimizing the velocity field, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the hub into distinct functional zones: the main hub body, the movable raised area, and the blade attachment region. This segmentation allows the raised area to be independently adjusted relative to the hub, enabling gap optimization without requiring complete redesign of the entire turbine structure.
Solution Approach 2:
The raised area acts as an intermediary element between the blade and the hub. Instead of directly adjusting the blade position or hub geometry, the raised area serves as a movable mediator that can be positioned to create the desired gap, simplifying the overall control mechanism while achieving efficient velocity field management.
Data Source
AI summary
A turbine unit for a hydraulic installation, and more in particular it deals with the hub of the turbine unit. The present invention proposes to provide means for adjusting a gap extent formed between the hub and the inner edge of the blade, this way dramatically increasing the performance of the turbine.