Gas Turbine Rotor Internal Cavities via Dissolvable Sacrificial Tubes
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Solution Overview
Problem
Conventional machining techniques are inadequate for producing shaped internal cavities within gas turbine engine rotors, particularly those with complex three-dimensional geometries, as they lack accessibility from the exterior, making it impractical to create features like stress relief tunnels or cooling passages.
Innovation Solution
The method involves embedding elongated sacrificial tubes with solvent inlet channels into a PM body, consolidating them using hot isostatic pressing, and then chemically dissolving the tubes to create shaped cavities, which can be further processed to produce the final rotor, reducing the dissolution time and minimizing acid attack by using solvent inlet channels filled with non-compressible materials or reinforcement structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional machining techniques are used to produce internal cavities, then manufacturing simplicity is maintained, but complex three-dimensional cavities with poor accessibility cannot be produced
Solution Approach 1:
Sacrificial tubes with internal channels are pre-positioned within the PM body before consolidation. These tubes serve as templates for the desired cavity geometry, allowing complex three-dimensional cavities to be formed without requiring post-consolidation machining access to difficult-to-reach areas.
Solution Approach 2:
The mechanical machining process is replaced with a chemical dissolution process. Instead of mechanically removing material to create cavities, acid is introduced through the sacrificial tube channels to chemically dissolve the PM material, enabling formation of complex cavities that would be inaccessible to machining tools.
2Manufacturing precision
If sacrificial tubes are removed by chemical dissolution, then shaped internal cavities are created, but dissolution time becomes excessively long
Solution Approach 1:
The dissolution process is segmented by introducing acid through multiple distributed channels within the sacrificial tubes rather than through a single access point. This multi-channel approach allows simultaneous dissolution at multiple locations throughout the PM body, dramatically reducing the overall dissolution time while maintaining precise cavity geometry.
Solution Approach 2:
The dissolution process transitions from a surface-level or single-point attack to a three-dimensional distributed attack pattern. Acid is delivered through channels extending deep into the PM body, enabling simultaneous dissolution throughout the volume and reducing the time required to achieve complete cavity formation.
3Manufacturing precision
If acid is used to dissolve sacrificial tubes, then internal cavities are formed, but acid attack damages the surrounding PM material
Solution Approach 1:
The sacrificial tubes act as intermediaries that control and contain the acid delivery process. Acid is introduced through these tubes which protect the surrounding PM material from direct acid contact, allowing dissolution to occur only at the intended cavity locations while minimizing harmful side effects on the rotor structure.
Solution Approach 2:
The acid dissolution effect is localized to specific regions where the sacrificial tubes are positioned. By controlling the location, orientation, and distribution of sacrificial tubes, the acid attack is confined to precise areas needed for cavity formation, preventing widespread damage to the PM material while achieving the desired cavity geometry.
4Manufacturing precision
If elongated sacrificial tubes are used to create deep cavities, then complex internal geometries are achieved, but tube collapse occurs during HIP processing
Solution Approach 1:
The sacrificial tubes are constructed as composite structures with walls made of materials that provide both the desired cavity geometry and sufficient mechanical strength to withstand HIP processing pressures. This composite approach allows the tubes to maintain their elongated shape and internal channels while resisting collapse during the high-pressure consolidation process.
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 approach allows for the efficient production of gas turbine engine rotors with complex internal cavities, reducing the dissolution time of sacrificial tubes to a few hours, minimizing acid attack, and preventing tube collapse during the HIP process, thereby enhancing the manufacturing efficiency and durability of the rotor components.
Implementation Method 1
Acid or another solvent is directed into solvent inlet channels provided in the elongated sacrificial tubes to chemically dissolving the elongated sacrificial tubes and create shaped cavities within the rotor preform
Implementation Method 2
The HIP container is then subject to elevated temperatures and isostatic pressures sufficient to consolidate or sinter the PM alloy into a coherent mass or component preform
Data Source
AI summary
Embodiments of a methods for producing gas turbine engine rotors and other powdered metal articles having shaped internal cavities are provided. In one embodiment, the method includes consolidating a powdered metal body utilizing a hot isostatic pressing process to produce a rotor preform in which elongated sacrificial tubes are embedded. Acid or another solvent is directed into solvent inlet channels provided in the elongated sacrificial tubes to chemically dissolving the elongated sacrificial tubes and create shaped cavities within the rotor preform. The rotor preform is subject to further processing, such as machining, prior to or after chemical dissolution of the elongated sacrificial tubes to produce the completed gas turbine engine rotor.