Aircraft Engine Impeller With Dual-Material Hub for Cold Dwell and Creep
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Solution Overview
Problem
Impellers of aircraft engines face challenges due to temperature gradients, leading to issues such as cold dwell and creep, which limit the choice of materials and restrict outlet air temperatures, as existing materials are either susceptible to cold dwell or creep at different temperature thresholds.
Innovation Solution
The impeller is designed with two distinct materials, one for creep resistance and another for cold dwell resistance, with the outer hub body made of Ti-834 and the inner hub body made of Ti-6246, separated by an annular gap to manage thermal gradients and prevent failure modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single material is used for the impeller, then the manufacturing process is simple, but the impeller cannot simultaneously resist both cold dwell and creep under temperature gradients
Solution Approach 1:
The impeller is divided into two distinct material zones: an inner hub body made of Ti-6246 alloy resistant to cold dwell, and an outer hub body made of Ti-834 alloy resistant to creep. This segmentation allows each material to be optimized for its specific thermal environment, with the inner material protecting against cold dwell in cooler regions and the outer material protecting against creep in hotter regions.
Solution Approach 2:
Different materials are assigned to different regions of the impeller based on local thermal conditions. The inner hub body uses Ti-6246 alloy specifically for its cold dwell resistance in cooler regions, while the outer hub body uses Ti-834 alloy specifically for its creep resistance in hotter regions, creating local material optimization.
2Temperature
If materials resistant to cold dwell are used, then cold dwell is prevented, but the outlet air temperature is limited due to inability to withstand hot temperatures
Solution Approach 1:
The impeller is segmented into inner and outer hub bodies with different materials. The inner hub body made of Ti-6246 alloy provides cold dwell resistance, enabling the use of higher outlet air temperatures in the outer regions without compromising the entire impeller's reliability.
Solution Approach 2:
The impeller uses a composite structure combining Ti-6246 alloy and Ti-834 alloy. This composite material approach allows the impeller to simultaneously exhibit cold dwell resistance from the Ti-6246 inner hub and high temperature creep resistance from the Ti-834 outer hub, enabling higher outlet air temperatures.
3Reliability
If dual material construction is used, then resistance to both cold dwell and creep is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The manufacturing process is segmented into two main stages: first fabricating the inner hub body from Ti-6246 alloy, then fabricating the outer hub body from Ti-834 alloy and assembling them together. This segmentation allows each material to be processed under its optimal conditions while simplifying the overall manufacturing approach.
Solution Approach 2:
The manufacturing process merges two separately fabricated hub bodies into a single integrated impeller assembly. The inner hub body and outer hub body are combined through mechanical assembly, creating a dual-material impeller that achieves both cold dwell and creep resistance.
Data Source
Figure 1
Figure 2
AI summary
An impeller (30) for a centrifugal compressor (20), the impeller (30) rotatable about a central axis (11), has: an outer hub body (32) including a first material and extending around the central axis (11), the outer hub body (32) defining a gaspath face (32A) extending from an inlet (30I) to an outlet (30O), the gaspath face (32A) extending radially away from the central axis (11) from the inlet (30I) to the outlet (30O); blades (33) protruding from the gaspath face (32A) and circumferentially distributed around the central axis (11); and an inner hub body (34) extending around the central axis (11), the inner hub body (34) secured to the outer hub body (32), the outer hub body (32) axially overlapping and extending around the inner hub body (34), the inner hub body (34) made of a second material being more cold dwell resistant than the first material.