Segmented Flywheel Stack to Limit Stress Transfer and Cracking
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Solution Overview
Problem
Existing flywheel designs face challenges in withstanding high centrifugal stresses at high peripheral speeds while ensuring safety and reducing manufacturing costs.
Innovation Solution
The flywheel design features a stack of discs with disc apertures and plate members that are clamped together without contacting the discs, minimizing stress transfer and preventing cascade failures. Additionally, the use of partial bonding between discs and plate members further enhances safety by limiting crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the flywheel operates at high peripheral speeds to increase energy storage capacity, then the energy storage capacity is improved, but the centrifugal stresses increase causing safety risks
Solution Approach 1:
The inertia element is divided into multiple discs stacked together, with circumferential spacing between them. This segmentation prevents crack propagation across the entire structure and allows the flywheel to operate at high speeds (above the speed of sound) while maintaining safety. The discs are connected through connection means that extend through apertures, creating a segmented but cohesive structure.
2Stability of the object's composition
If connection means contact the discs to secure them, then the structural integrity is improved, but the stress transfer to discs increases causing potential failure
Solution Approach 1:
Connection means (such as bolts or pins) extend through apertures in the discs but do not contact the disc surfaces. The connection means act as intermediaries that secure the stacked discs together through the apertures without transferring centrifugal stresses directly to the disc material, thereby maintaining structural integrity while minimizing stress transfer.
3Strength
If full bonding between discs and plate members is used to ensure strength, then the strength is improved, but crack propagation risk increases causing catastrophic failure
Solution Approach 1:
Bonding is applied selectively only to peripheral regions of the discs, not to the entire surface. This local bonding approach provides sufficient strength to hold the stacked discs together while leaving the central regions unbonded, which prevents crack propagation across the entire structure. If a crack initiates, it remains localized and cannot spread throughout the entire inertia element.
4Ease of manufacture
If monolithic steel inertia element is used for simplicity, then the manufacturing cost is reduced, but the containment requirements increase leading to high installation cost
Solution Approach 1:
The inertia element is segmented into multiple discs with spacing between them, which fundamentally changes the failure mode. Instead of a single catastrophic failure as in monolithic structures, the segmented design allows for localized failures that do not compromise the entire structure. This reduces the containment requirements and allows above-ground installation without expensive thick containment vessels or underground bunkers.
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 allows for safe operation at high rotational speeds, achieving kinetic energy storage capacities of at least 100 kJ and peripheral speeds of up to 350 m/s, while reducing the risk of catastrophic failures and lowering manufacturing costs.
Implementation Method 1
A major design challenge for inertia elements used in the energy storage class of flywheels is how to withstand the high centrifugal stresses induced by the high peripheral speeds
Implementation Method 2
The inertia element stores energy by virtue of its angular momentum; the faster it rotates, the more energy is stored, with energy storage being proportional the square of angular speed
Data Source
AI summary
A flywheel (1100) comprising a plurality of discs (1102) arranged in a stack (1104), including at least first and second end discs at either end of the stack (1104), each of the plurality of discs (1102) including a plurality of disc apertures therethrough, first and second plate members (1106) disposed at opposing ends of the stack (1104), one or both of the first and second plate members (1106) including a plurality of plate apertures (1106a) therethrough for alignment with a corresponding series of disc apertures through the stack (1104), in which one or both of the plate members (1106) includes one or more recesses (1106c) which are disposed on a disc-facing side thereof and positioned adjacent to one or more of the plurality of plate apertures (1106a), and connection means (1114) for clamping the first and second plate members (1106) together about the stack of discs, the connection means (1114) extending through each of the plurality of disc apertures, in which a spacer or space-filling means (1138) is provided between the or each connection means (1114) and the respective disc apertures for supporting the connection means (1114), the spacer or space-filling means (1138) extending from a position within the stack (1104) into the one or more recesses (1106c) of one or both of the plate members (1106).