Retaining-Wire Joint Assembly for Thermal Expansion and Radial Stability
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Solution Overview
Problem
Conventional nut and bolt configurations in gas turbine engines face issues such as thermal cycling problems, weight increase, and aerodynamic disruption, along with unwanted radial movement in existing joint assemblies, which complicate assembly and maintenance.
Innovation Solution
A joint assembly featuring a connection member insertable into a cavity formed by concavities on opposing surfaces, with a tenon and slot arrangement to prevent axial and radial separation, and a resilient retaining member to interlock the components, allowing for secure assembly and maintenance while accommodating differential thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional nut and bolt configurations are used to secure engine components, then the components can be joined together, but the bolts tend to gall and seize due to thermal cycling, requiring expensive and time-consuming drilling out during disassembly
Solution Approach 1:
The connection member is divided into distinct functional segments: a body portion with a head for insertion, a shank for engagement, and a tail for actuation. This segmentation allows the joint to be easily disassembled by actuating the tail to release the shank from the cavity, eliminating the need for drilling out seized bolts.
Solution Approach 2:
The connection member acts as an intermediary element that joins the first and second components without creating permanent bonds. The cavity in the second component provides a receptacle for the connection member, allowing for reversible assembly and disassembly, contrasting with conventional nuts and bolts that gall and seize under thermal cycling.
2Strength
If nuts and bolts are used to join components, then the components can be secured, but suitable flanges must be provided on the parts which adds to weight and increases assembly time
Solution Approach 1:
The invention extracts the joining function from heavy flange structures and concentrates it in the lightweight connection member. The cavity in the second component provides the necessary engagement feature, eliminating the need for bulky flanges on both components. This significantly reduces the overall weight while maintaining joint strength.
Solution Approach 2:
Instead of providing joining features (flanges) across entire component surfaces, the invention localizes the joining function to specific points: the cavity in the second component and the corresponding connection member. This localized approach minimizes weight while maintaining sufficient joining capability.
3Strength
If bolts heads are positioned in the gas flow path to secure components, then the components can be joined, but the aerodynamics of the engine are disrupted and the bolt deterioration is accelerated
Solution Approach 1:
The invention extracts the connection function from bolt heads that would protrude into the gas flow path. The connection member is designed to be received within the cavity of the second component, with its head positioned in a recess or cavity that is not exposed to the gas flow. This eliminates aerodynamic disruption while maintaining joint strength.
Solution Approach 2:
The connection member is oriented axially along the common axis of the components, with the head, shank, and tail arranged in the axial dimension. This axial orientation allows the connection to be made without protruding elements in the radial direction where gas flow occurs, thus avoiding aerodynamic disruption.
4Stability of the object's composition
If a wire is used as a connection member in an annular cavity, then the components can be locked together, but unwanted radial movement occurs between the opposing faces of the joint
Solution Approach 1:
The connection member features an asymmetric geometry with a head of larger diameter than the shank, and a tail for actuation. The head engages with the cavity to prevent radial movement, while the shank provides axial connection. This asymmetric design provides both radial stability and axial strength, resolving the contradiction between joint stability and radial movement resistance.
Solution Approach 2:
The head of the connection member has a curved or rounded surface that interfaces with the cavity walls, providing optimal contact for preventing radial movement. The curved geometry distributes contact stresses and enhances the prevention of unwanted radial movement between opposing faces while maintaining overall joint strength.
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
The joint assembly provides a secure, lightweight, and aerodynamically efficient connection that minimizes assembly time and weight, while accommodating thermal expansion and reducing the risk of radial movement, thus enhancing the reliability and efficiency of gas turbine engines.
Implementation Method 1
US 2014/0161510 A1 proposes to use a material of greater thermal coefficient of expansion for the wire than that of either of the two components so that the wire is a close fit in the annular cavity when the joint is at elevated temperature
Data Source
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AI summary
A joint assembly (24) for joining first (28) and second (26) components about a common axis (25). The first component (28) has a first end portion (46) having a radially outwardly facing surface shaped to fit radially inside a second surface of a hollow second end portion of the second component (26) so as to form an interface (50) between the opposing first and second surfaces. The first and second surfaces each comprise a concavity (56, 58) extending laterally with respect to the axis (25) such that when the first and second surfaces are opposingly arranged the opposing concavities (56, 58) define a cavity (55) at the interface. A retaining member (54) such as a wire is insertable into the cavity (55) at the interface (50) to prevent axial separation of the first (28) and second (26) components. One of the first (46) and second end portions has a free end in the form of a protrusion (40) axially spaced from the concavity (56) and the other of the first and second end portions comprises an axially extending recess (42) arranged to receive the free end (40). A lapped and/or scarfed joint assembly may be provided. A tenon may be provided to prevent lateral movement of the joint once assembled.