Supercritical Power Shaft Dynamic Shock Absorbing Architecture
Solution Overview
Problem
Supercritical power shafts in turbine engines face challenges with damping due to their high operating ranges exceeding the first critical speed, leading to overvoltage phenomena and amplified deformations, which conventional damping methods like squeeze films cannot address effectively, especially when power teeth are present, as they require radial displacement incompatible with tooth frame bearings.
Innovation Solution
A dynamic compressible damping architecture is introduced, extending the bearing downstream with a flexible connection and an additional axially eccentric damping support, allowing for adjustable stiffness and deformation energy distribution, ensuring damping without compromising torque transmission or causing disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If squeeze film damping is used on bearings, then damping effect is improved, but radial displacement is required which is incompatible with tooth frame bearings
Solution Approach 1:
A flexible connection element is introduced as an intermediary between the bearing and the shaft. This flexible connection provides the necessary radial displacement for squeeze film damping while maintaining the rigidity required by tooth frame bearings, thus resolving the incompatibility between damping requirements and bearing rigidity constraints
Solution Approach 2:
The bearing system is made dynamically adaptable by allowing controlled radial displacement through the flexible connection only when needed for damping during critical speed passage, while maintaining rigid support for torque transmission during normal operation. This dynamic behavior enables the system to switch between damping mode and rigid support mode
2Reliability
If rear bearings are used for damping, then damping is achieved, but modern architectures exclude rear bearings from modal deformation
Solution Approach 1:
The damping function is relocated from the radial dimension at rear bearings to the axial dimension at front bearings. The flexible connection enables axial movement that provides damping while the bearing itself maintains radial rigidity for torque transmission, effectively moving the damping mechanism to a different dimensional space where it doesn't conflict with architectural constraints
3Power
If front bearings are made rigid for torque transmission, then torque transmission is improved, but damping capability deteriorates
Solution Approach 1:
The front bearing assembly is segmented into two functional components: the bearing itself which provides rigid radial support for torque transmission, and the flexible connection which provides axial compliance for damping. This segmentation allows each component to optimize its specific function without compromising the other
Solution Approach 2:
Different parts of the bearing assembly are given different mechanical properties: the bearing races and rollers maintain high radial stiffness for torque transmission, while the flexible connection element is designed with controlled axial compliance for damping. This local differentiation of mechanical properties resolves the contradiction between rigidity and damping
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 solution effectively reduces the resonance peak forces at critical speeds, from 4500 N to 1600 N, maintaining rigidity and preventing premature wear or disengagement, while achieving acceptable deformation energy distribution, thus providing sufficient damping and maintaining optimal torque transmission.
Implementation Method 1
a dynamic compressible damping is created as an extension of the bearing downstream of the mesh
Implementation Method 2
a compressible damping in orbital movement to form a downstream damping axially eccentric with respect to the upstream support
Implementation Method 3
This eccentric architecture provides dynamic damping
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
The invention relates to an architecture making it possible to provide the sufficient absorption of shocks for a power shaft while maintaining rigidity at the front bearings so as to not compromise the meshing of the power teeth of a drive pinion. For this purpose, compressible dynamic shock absorption is provided in alignment with the downstream shock absorber of the additional meshing. An assembly for dynamically absorbing shocks for a power shaft, according to the invention, comprises upstream (12) and downstream (14) bearings having power rollers (12r, 14r) mounted on two casings (32, 34) and flanking a speed-reducing teeth meshing (15). The downstream bearing (14) is coupled to at least one additional roller bearing (20, 20r) associated with a compressible shock absorber (26) so as to form a downstream shock absorber (20, 26) that is axially offset relative to the upstream bearing (12) opposite the teeth meshing (15). Both downstream bearings (12, 14) are connectable by a flexible frame (24) mounted on the common casing (34). The invention can be used for power-transmission shafts, in particular supercritical shafts in turbine engines.