Split Impeller Assembly for Coating Access and Torque Transfer
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Solution Overview
Problem
Small and medium-sized impellers for hydraulic turbines and pumps, such as Francis turbines, face challenges in applying wear-reducing coatings due to inaccessible blade channels and are costly to produce, with existing solutions requiring significant effort and being non-wear-resistant.
Innovation Solution
The impeller is designed with detachable parts that have contact surfaces aligned perpendicular to the axis of rotation, allowing for easy coating and production, using frictional connections and sealed surfaces to transmit torque efficiently, and featuring parallel contact surfaces for simplicity and ease of repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the impeller is manufactured as an integral casting or welded structure, then the structural strength is improved, but the accessibility of the impeller blade channel for coating application deteriorates
Solution Approach 1:
The impeller is divided into multiple impeller parts that are detachably connected via contact surfaces. This segmentation allows the blade channels to be accessed from both sides by removing individual impeller parts, solving the accessibility problem while maintaining structural integrity through proper connection design
2Ease of operation
If the impeller is designed in sections to improve coating accessibility, then the ease of coating is improved, but the manufacturing complexity deteriorates
Solution Approach 1:
The impeller is segmented into a small number of parts (typically 2-4) connected by simple contact surfaces, providing just enough division to enable coating access without creating excessive complexity
Solution Approach 2:
Individual impeller parts are designed to be detachably connected, allowing specific parts to be removed for coating access while leaving the rest of the impeller assembled. This selective extraction minimizes the disruption to the overall structure
3Manufacturing precision
If the contact surfaces are oriented perpendicular to the axis of rotation, then the manufacturing precision is improved, but the torque transmission capability deteriorates
Solution Approach 1:
The contact surfaces are designed with specific local geometric features (such as conical sections or stepped profiles) that concentrate the torque transmission at specific locations while maintaining the overall perpendicular orientation for ease of machining
Solution Approach 2:
Friction-enhancing films or coatings are applied to the contact surfaces to increase the coefficient of friction, enabling adequate torque transmission through friction alone without requiring complex surface geometries or additional mechanical interlocking features
4Ease of repair
If the impeller components are connected by friction, then the ease of repair is improved, but the reliability of connection deteriorates
Solution Approach 1:
The normal force applied to the friction contact surfaces is carefully optimized to generate sufficient friction force for reliable torque transmission during operation, while allowing easy separation when the normal force is reduced during maintenance
Solution Approach 2:
Friction-enhancing films or coatings are applied to the contact surfaces to increase the coefficient of friction, enabling reliable torque transmission with moderate normal forces and facilitating easy separation when needed for maintenance
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 design enables easy and cost-effective production and coating of impellers, minimizing wear and reducing operational risks, particularly in high-sand content environments, while maintaining hydraulic efficiency and simplicity in manufacturing and maintenance.
Implementation Method 1
a moment about the axis of rotation between the impeller parts can be transmitted essentially via forces tangential to the contact surfaces
Implementation Method 2
A friction-fit connection prevents contact corrosion, fretting (local welding), and tearing loose
Data Source
Figure 1~2
AI summary
The invention relates to a runner (1) for a hydraulic turbine, pump or pump turbine, in particular for a Francis turbine, which runner (1) can be mounted such that it can be rotated about a rotational axis (10) and has runner blades (4) which are arranged around the rotational axis (10) along a circumferential direction, wherein the runner (1) has at least two runner parts which are connected to one another via contact surfaces (9). In order to achieve a simple manufacturing capability, it is provided according to the invention that the contact surfaces (9) are positioned and oriented in such a way that a moment can be transmitted about the rotational axis (10) between the runner parts substantially via forces tangentially with respect to the contact surfaces (9).