Aircraft Engine Interference Assembly Using Thermal Expansion Pre-Assembly
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Solution Overview
Problem
Assembling parts of aircraft engines with tight tolerances and interference fits can be challenging due to the need for one part to be cooled while the other is heated, requiring manipulation of hot components, which can be hazardous and difficult to handle, especially when high temperatures are involved.
Innovation Solution
A method involving forming a pre-assembly of parts with different coefficients of thermal expansion, heating the assembly to expand the part with the higher expansion rate, and compressing it to create a contact interface, using supports and weights to align and secure the parts, such as a ceramic side plate and steel ring in a rotary internal combustion engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If one part is cooled and the other part is heated to achieve interference fit, then the assembly can be engaged with tight tolerances, but the hot parts require hazardous manipulation and difficult handling
Solution Approach 1:
The patent applies preliminary action by pre-assembling the components at room temperature before heating. The first component is inserted into the second component while both are at room temperature, creating a pre-assembly that is then heated together. This eliminates the need to handle hot components separately, as both parts are heated simultaneously in a furnace after pre-assembly, resolving the handling hazard while maintaining assembly precision.
Solution Approach 2:
The patent merges the heating process by heating both the first component and the second component simultaneously in the same furnace environment. Instead of heating one component separately and then handling it, both components are heated together after pre-assembly, combining the thermal processing steps and eliminating the need to manipulate hot parts individually.
2Manufacturing precision
If parts are assembled with interference fit, then tight tolerances are achieved, but the assembly process becomes complex requiring cooling and heating operations
Solution Approach 1:
The patent simplifies the process by performing the assembly action (inserting the first component into the second) before the thermal expansion action (heating). This preliminary assembly at room temperature creates a pre-assembly that is then heated together, eliminating the need for separate cooling and heating operations on individual components and reducing overall process complexity.
Solution Approach 2:
The patent changes the temperature parameter for both components simultaneously rather than applying different temperature treatments to each component separately. By heating both components together in the same thermal environment, the process becomes simpler while still achieving the necessary dimensional changes for interference fit.
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 method safely and effectively achieves an interference fit between components with different thermal expansion rates, facilitating the assembly of aircraft engine parts by allowing the parts to be assembled at a controlled temperature, reducing handling risks and ensuring precise alignment and contact.
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
Figure 1A
Figure 1B~1D
Figure 2
AI summary
A method of assembling parts of an aircraft engine includes: forming, at a first temperature, a pre-assembly of a first part (16) of the aircraft engine and a second part (17) of the aircraft engine by aligning the first part (16) and the second part (17) such as to be engageable within one another, the second part (17) having a coefficient of thermal expansion that is greater than a coefficient of thermal expansion of the first part (16); heating the pre-assembly to a second temperature greater than the first temperature to expand the second part (16) relative to the first part (16); and compressing the pre-assembly until the first part (16) is inserted into the second part (17) to create a contact interface (P) between the first part (16) and the second part (17).