Crescent-Dam Bearing Geometry for Turbocharger Rotor Stability
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Solution Overview
Problem
Bearing assemblies in turbochargers experience sub-synchronous motion, increased vibration, and noise due to cross-coupled stiffness and fluid film flow profiles, leading to reduced durability and unfavorable noise characteristics.
Innovation Solution
A bearing design featuring an axial channel with a modified crescent-shaped dam region between 90 and 180 degrees on its inner surface, which modifies the fluid film flow profile to reduce cross-coupled stiffness and enhance stability at high RPMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional bearing design is used, then the bearing assembly operates at high RPM, but cross-coupled stiffness increases causing sub-synchronous motion, vibration, and noise
Solution Approach 1:
The patent applies asymmetry by positioning the dam region at an asymmetric location on the bearing surface, specifically at an angular position between 30 and 150 degrees from the axial centerline. This asymmetric placement modifies the fluid film pressure distribution to reduce cross-coupled stiffness and eliminate sub-synchronous motion, thereby improving rotor stability at high speeds without sacrificing speed performance
2Device complexity
If a conventional bearing design is used, then the bearing structure is simple, but vibration and noise increase due to cross-coupled stiffness
Solution Approach 1:
The patent applies local quality by introducing a localized dam region with specific geometric characteristics (angular position, radial depth, and axial width) on the bearing surface. This localized modification creates a targeted change in fluid film pressure distribution at the dam region, reducing cross-coupled stiffness and harmful vibrations without requiring complex global structural changes to the entire bearing assembly
3Ease of manufacture
If the dam region is positioned at standard locations, then manufacturing is straightforward, but fluid film flow profile modification is insufficient to reduce cross-coupled stiffness
Solution Approach 1:
The patent applies parameter changes by optimizing the dam region's geometric parameters including angular position (30-150 degrees from axial centerline), radial depth (0.001-0.005 inches), and axial width (0.02-0.08 inches). These parameter modifications create the appropriate fluid film pressure distribution to reduce cross-coupled stiffness while maintaining manufacturability through conventional machining processes
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
The modified fluid film flow profile results in greater static eccentricity, reducing cross-coupled stiffness and stabilizing rotor response, thereby improving durability and reducing noise and vibration in bearing assemblies.
Implementation Method 1
a fluid film between the rotor and the bearing; and rotating the rotor within the bearing such that the dam region provides for an axial fluid film flow modification
Data Source
AI summary
A bearing comprising an axial channel formed along a longitudinal axis of the bearing having an inner radius comprising an inner surface and an outer radius comprising an outer surface and at least one dam region formed on the inner surface of the inner radius of the channel wherein the dam region comprises a modified crescent shape between 90 and 180 degrees about the longitudinal axis of the channel.