Rotor Midlength Balancing via Axial Pockets and Slots
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Solution Overview
Problem
High-speed rotors face limitations in balancing due to highly stressed materials that cannot tolerate weight-addition or weight-removal features, restricting midlength balancing and thus limiting operating speed ranges, as traditional balancing methods are restricted to end regions and require complex bearing mechanisms.
Innovation Solution
The implementation of axially extended pockets and slots within the rotor assembly allows for midlength balancing by positioning balance weights or removing mass from these features, enabling correction of residual unbalance at axial locations between the end regions post-assembly, thereby increasing operational speeds without instability issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional balancing methods are used with weight-addition or weight-removal features in end regions, then balancing can be achieved, but the highly stressed outer shell material cannot tolerate the stress concentrations, limiting the rotor to end-region balancing only
Solution Approach 1:
The patent divides the rotor into multiple balancing planes (end regions and midlength regions) with separate balancing capabilities. Each plane can be independently balanced using balance weights positioned in pockets or slots at specific locations, allowing distributed unbalance correction rather than concentrating all balancing features in the end regions where material stress is lower.
Solution Approach 2:
The patent extends balancing capability from the traditional one-dimensional end-region approach to a three-dimensional approach by introducing midlength balancing planes within the rotor body. This allows balance weights to be positioned at multiple axial locations (z-axis), radial distances (r-axis), and angular positions (θ-axis), creating a comprehensive balancing system that operates in multiple spatial dimensions simultaneously.
2Strength
If correction planes are available only in the end regions, then material stress is reduced, but the speed range over which the rotor can operate without rotor dynamic instability is limited
Solution Approach 1:
The rotor is segmented into multiple balancing planes including end regions and midlength regions. Each plane contains pockets or slots that can accommodate balance weights, creating distributed correction locations throughout the rotor body. This segmentation allows unbalance forces to be corrected at multiple axial positions, expanding the stable operating speed range.
Solution Approach 2:
The patent changes the spatial distribution parameter of balancing features from concentrated at ends to distributed throughout the rotor body. By introducing midlength balancing planes with pockets and slots at various radial and angular positions, the system transforms the balancing capability from limited end-region correction to comprehensive multi-plane correction, enabling operation at higher speeds.
3Reliability
If high stiffness is designed into the rotor to correct residual unbalance at end regions, then balancing is possible, but the size and speed that the rotor can operate are restricted
Solution Approach 1:
Instead of relying solely on high stiffness and end-region balancing, the patent segments the rotor into multiple balancing planes with independent correction capabilities. Each plane can address specific unbalance components, providing versatile correction options that accommodate various rotor sizes and operating speeds without requiring excessive stiffness.
Solution Approach 2:
The patent adds axial dimension to the balancing capability by introducing midlength balancing planes. This multi-dimensional approach allows the rotor to be balanced effectively across different size ranges and speed regimes, enhancing adaptability without compromising structural stiffness or requiring oversized design.
4Ease of manufacture
If access to balance correction locations is restricted by rotor support structure and non-rotating machine components, then balancing operations must be conducted before rotor assembly, but this requires significant disassembly for future balance correction
Solution Approach 1:
The patent incorporates pockets and slots for balance weights directly into the rotor body during manufacturing, creating pre-prepared balancing locations that are accessible after assembly. This preliminary integration of balancing features eliminates the need for future disassembly, as the balance correction locations are built-in and accessible through the rotor structure itself.
Solution Approach 2:
The rotor design integrates multiple functions into the balance correction system: the pockets and slots serve both structural purposes and balancing purposes. The balance weights can be installed and adjusted after rotor assembly, providing universal accessibility for balancing operations without requiring machine disassembly, thus simplifying maintenance and adjustment procedures.
Data Source
AI summary
A midlength balanced rotor comprises a rotor assembly for rotation about an axis of rotation defining at least one of an axially extended, radially concentric, centerline borehole; an array of radially or tangentially distributed, axially extended pockets; and a series of radially or tangentially distributed, axially extended slots. At least one balance weight is positioned within at least one of the axially extended, radially concentric, centerline borehole, the array of radially or tangentially distributed, axially extended pockets, or the radially or tangentially distributed, axially extended slots to balance the rotor assembly. Alternatively, at least one balance correcting mass is removed from at least one of the axially extended, radially concentric, centerline borehole, the array of radially or tangentially distributed, axially extended pockets, or the radially or tangentially distributed, axially extended slots to balance the rotor assembly. In addition, a method of midlength balancing a rotor comprises the steps of providing a rotor assembly with at least one of an axially extended, radially concentric, centerline borehole; an array of radially or tangentially distributed, axially extended pockets; and a series of radially or tangentially distributed, axially extended slots; rotating the rotor shaft about an axis of rotation; determining unbalance of the rotor shaft; and adding or removing weight to at least one of said an axially extended, radially concentric, centerline borehole; array of radially or tangentially distributed, axially extended pockets; or series of radially or tangentially distributed, axially extended slots, to balance the rotor shaft.