Aircraft Engine Interference-Fit Assembly Using Thermal Expansion
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Solution Overview
Problem
Assembling aircraft engine parts with tight tolerances and interference fits requires handling hot parts, which can be challenging due to differing coefficients of thermal expansion, especially when one part needs to be heated to expand sufficiently for insertion.
Innovation Solution
A method involving pre-assembly of parts with different thermal expansion coefficients, where one part is heated to a higher temperature to expand, and then compressed into the other part while maintaining alignment, using supports and weights to create a contact interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If one part is heated to expand it for insertion into another part, then the interference fit assembly is achieved, but the handling difficulty and safety risks increase due to high temperature manipulation
Solution Approach 1:
The method performs preliminary alignment of the two parts at room temperature before heating. The parts are pre-assembled in their correct relative positions while cool, then the entire assembly is heated together. This eliminates the need to handle hot parts for alignment purposes, as the preliminary positioning is done safely at low temperature.
Solution Approach 2:
The invention uses a fixture or jig as an intermediary device to hold and align the parts during the heating process. This intermediary structure allows the parts to be heated in place without requiring manual manipulation of the hot components, thereby improving safety and ease of operation.
2Manufacturing precision
If parts with different coefficients of thermal expansion are assembled, then the interference fit can be achieved through heating, but the complexity of the assembly process increases due to temperature control requirements
Solution Approach 1:
The invention combines the alignment and heating operations into a single integrated process. By pre-assembling the parts in the correct configuration before heating, and then heating the entire assembly together, the method eliminates the need for separate alignment and heating steps, reducing overall process complexity despite the temperature control requirements.
3Manufacturing precision
If the second part is heated to expand relative to the first part, then the interference fit is achieved, but the risk of thermal damage or deformation increases
Solution Approach 1:
The invention heats both parts simultaneously in the same thermal environment rather than heating one part separately. This combined heating approach ensures uniform temperature distribution and prevents localized overheating that could cause thermal damage or deformation, while still achieving the necessary expansion differential due to the different coefficients of thermal expansion of the two materials.
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
Facilitates safe and precise assembly of parts with interference fits by managing thermal expansion, ensuring proper alignment and contact without excessive handling of high-temperature components.
Implementation Method 1
heating the pre-assembly to a second temperature greater than the first temperature to expand the second part relative to the first part
Data Source
AI summary
A method of assembling parts of an aircraft engine, the method includes: forming, at a first temperature, a pre-assembly of a first part of the aircraft engine and a second part of the aircraft engine by aligning the first part and the second part such as to be engageable within one another, the second part having a coefficient of thermal expansion that is greater than a coefficient of thermal expansion of the first part; heating the pre-assembly to a second temperature greater than the first temperature to expand the second part relative to the first part; and compressing the pre-assembly until the first part is inserted into the second part to create a contact interface between the first part and the second part.