Gas Turbine Exhaust Diffuser Liner Fixation for Thermal Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In gas turbines, the fixation of liners in the exhaust diffuser section is challenging due to thermal expansion differences between the cold support structure and hot liner, which creates thermal bridges, and requires a smooth surface to avoid disturbing the exhaust flow, while existing solutions like U profiles and threaded joints are inefficient and prone to failure.
Innovation Solution
A diffuser design featuring C profiles welded to the liner segments with a slotted guiding channel and T supports that engage with the support structure, allowing for axial expansion and minimizing heat transfer, along with overlapping segments for stiffness and a smooth surface, and a gudgeon-based fixing mechanism to secure the liner segments without obstructing the exhaust flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threaded joints and U profiles are used to fix the liner, then the liner can be secured to the support structure, but thermal bridges are created and the surface is disturbed causing flow turbulence
Solution Approach 1:
The harmful threaded joints and U profiles that create thermal bridges and flow disturbances are completely removed from the exhaust flow side. The fixation system is repositioned to the rear side of the liner, extracting the harmful elements from the flow path while maintaining fixation functionality.
Solution Approach 2:
A new intermediary fixation system is introduced consisting of fixation elements on the rear side of the liner that connect to the support structure without extending into the flow. This mediator system provides secure fixation while maintaining a smooth flow surface, using elements that can be welded to the liner rear side and engage with the support structure.
2Loss of energy
If the support structure is kept cold and the liner is exposed to hot exhaust gas, then thermal insulation is improved, but different thermal expansions create fixation difficulties
Solution Approach 1:
The fixation system is designed to be dynamic rather than rigid, allowing for thermal expansion differences between the cold support structure and hot liner. The fixation elements can accommodate movement and expansion while maintaining secure connection, adapting to the changing thermal conditions during operation.
Solution Approach 2:
The fixation design explicitly accounts for and accommodates thermal expansion by using elements that can move or deform with the expanding liner. The fixation system allows the liner to expand freely while maintaining attachment, preventing stress buildup and fixation failure due to differential thermal expansion.
3Strength
If longitudinal ribs are added to the liner for structural support, then the liner strength is improved, but the diffuser efficiency is reduced due to disrupted exhaust flow
Solution Approach 1:
The liner is divided into multiple longitudinal segments that can be joined without requiring prominent longitudinal ribs. The segmentation allows for structural integrity through controlled joints while maintaining a smoother surface compared to traditional ribbed structures, reducing flow disturbance in the diffuser section.
Solution Approach 2:
Structural reinforcement is applied locally only where absolutely necessary, rather than using continuous longitudinal ribs along the entire liner. The reinforcement is concentrated at specific locations such as joints or high-stress areas, allowing the majority of the liner surface to remain smooth for optimal flow characteristics.
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 solution provides a safe and efficient fixation that compensates for thermal expansions, maintains a smooth surface, and prevents thermal stress and turbulence, enhancing the diffuser's performance and reliability by ensuring the liner segments can expand freely and rotate, reducing the risk of fixation failure.
Implementation Method 1
an insulation filling the space between said conical liner and said support structure
Implementation Method 2
The weld seam, which can for example be a fillet seam, leads to a good heat flow from the liner to the C profiles
Implementation Method 3
as the support structure is cold and the liner is hot, there are different thermal expansions
Data Source
AI summary
The invention relates to a diffuser (11) for the exhaust section of a gas turbine (10), comprising at least one cone (13, 14) extending along a machine axis and bordering a channel for an exhaust flow, whereby said at least one cone (13, 14) has a wall with an internal structure comprising a plurality of longitudinal liner segments (29) extending in axial direction and establishing a conical liner (15a,b) being in contact with the exhaust flow, a support structure (17a,b) coaxially arranged with respect to said conical liner (15a,b) in a predetermined distance, and an insulation (16a,b) filling the space between said conical liner (15a,b) and said support structure (17a,b). A smooth inner surface and a safe compensation of different thermal expansions are achieved by having each of said liner segments (29, 30) fixed in lateral direction at one fixing point (35), and having each liner segment (29, 30) supported at a plurality of distributed points outside said fixing point (35) by means of supporting elements (26a,b, 31a,b), which are confined to the space between said conical liner (15, 15a,b) and said support structure (17, 17a,b) and allow for a lateral thermal expansion of the liner segments (29, 30).