Turbocharger Compressor Wheel Renewal via Shot Peening
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Solution Overview
Problem
Turbocharger compressor wheels experience fatigue failure due to high speeds, leading to expensive replacements, as existing methods discard wheels with cracks exceeding 200 microns without considering compressive stress zones for renewal.
Innovation Solution
A method involving non-destructive inspection using ultrasonic and eddy current testing to identify compressor wheels with cracks within specified lengths, followed by shot peening to impart compressive residual stresses in high-fatigue regions, allowing for the extension of compressor wheel service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compressor wheels are replaced when cracks exceed 200 microns, then reliability is maintained, but loss of substance increases due to premature discarding of serviceable wheels
Solution Approach 1:
The patent changes the decision parameter for wheel disposal from a fixed crack length threshold (200 microns) to a condition-based threshold that accounts for crack location relative to the compressive stress zone. Wheels with cracks within the compressive stress zone are renewed and returned to service, while only wheels with cracks outside this zone are discarded. This parameter change allows continued use of wheels that would otherwise be discarded, reducing loss of serviceable wheels while maintaining reliability.
Solution Approach 2:
The patent applies preliminary shot peening treatment to compressor wheels before they are discarded, creating a compressive stress zone that can contain and heal cracks. This preliminary action transforms wheels that would become waste into serviceable components, directly addressing the loss of substance problem while maintaining reliability through the stress-induced crack closure mechanism.
2Duration of action of moving object
If shot peening is applied to all compressor wheels, then service life is extended, but device complexity and cost increase
Solution Approach 1:
The patent applies shot peening locally only to compressor wheels that pass inspection criteria (cracks within acceptable limits and positioned within the compressive stress zone). Rather than treating all wheels uniformly, the process selectively applies renewal treatment based on individual wheel condition, reducing overall device complexity and cost while still extending service life of eligible wheels.
Solution Approach 2:
The patent implements a feedback loop where compressor wheels are inspected, evaluated against established criteria, and then either renewed or discarded based on that evaluation. This feedback mechanism ensures that shot peening is applied only when beneficial, optimizing the balance between service life extension and process complexity/cost.
3Reliability
If non-destructive examination is conducted to detect small cracks, then reliability is improved by identifying serviceable wheels, but measurement precision requirements and inspection complexity increase
Solution Approach 1:
The patent changes the measurement precision requirement from detecting all cracks regardless of size or location to specifically detecting cracks relative to the compressive stress zone boundaries. This parameter change allows use of less precise inspection methods while still achieving reliable identification of serviceable wheels, as the critical measurement is crack position relative to the stress zone rather than absolute crack size.
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
Enables the reuse of compressor wheels with extended service life, reducing replacement costs and maintaining performance by identifying and treating wheels with cracks up to 200 microns, thereby increasing their operational hours.
Implementation Method 1
The inspection step comprises inspecting the back face of the compressor wheel using ultrasonic inspection
Implementation Method 2
inspecting the front face of the compressor wheel in the vicinity of the blade roots using eddy current testing
Implementation Method 3
the renewing step comprises peening to impart compressive residual stresses in those surface regions of the compressor wheel subject to the highest fatigue loadings
Data Source
AI summary
A method is provided for extending the service life of a used metallic compressor wheel having a damaged surface. The method generally comprises the steps of inspecting the used compressor wheel for material discontinuities such as fatigue cracks and, if fatigue cracks exceeding a predetermined length are not present, renewing the used compressor wheel such as by peening. The inspection process comprises conducting a non-destructive examination of the used compressor wheel to detect cracks larger than those which would fall generally within the compressive stress zone that is generated by peening.