Hot Gas Casing Fastening Web Slots for Thermal Stress Relief
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Solution Overview
Problem
Thermal stresses in the transition area between the inner wall and the fastening web of hot-gas-carrying housings in gas turbine systems lead to cracking, necessitating improved cooling methods that reduce maintenance and repair costs.
Innovation Solution
The fastening web is designed with a series of axial slots and through-openings, specifically T-shaped with curved ends and parabolic free ends, to alleviate thermal stresses and enhance cooling efficiency, while maintaining a reduced cooling air consumption and wear on the fastening web.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the fastening web is cooled more intensively to reduce thermal stresses, then the service life of the transition area is improved, but the cooling air consumption increases and the fastening web wear increases
Solution Approach 1:
The fastening web is segmented by providing multiple cooling openings instead of a single large opening. This segmentation allows cooling air to be distributed to multiple locations along the fastening web, reducing thermal stresses more effectively while using less total cooling air compared to a single large opening approach.
Solution Approach 2:
Cooling openings are provided at specific locations on the fastening web where thermal stresses are most critical. The cooling air is directed locally to these high-stress areas rather than uniformly across the entire fastening web, optimizing cooling efficiency and reducing overall air consumption.
2Duration of action of stationary object
If the fastening web is cooled more intensively to reduce thermal stresses, then the service life of the transition area is improved, but the fastening web wear increases
Solution Approach 1:
By segmenting the cooling function into multiple small openings rather than one large opening, the fastening web maintains better structural integrity. The segmented approach reduces wear because the cooling air flow is distributed and does not concentrate erosive forces on a single area, extending the fastening web's service life.
Solution Approach 2:
Cooling openings are strategically positioned in areas of highest thermal stress while avoiding regions where concentrated cooling air flow would cause excessive wear. This localized cooling approach protects critical areas from thermal damage while minimizing wear in load-bearing regions.
3Temperature
If cooling air openings are provided in the annular shoulder to cool the fastening web, then thermal stresses are reduced, but the transition area becomes very hot due to insufficient cooling distribution
Solution Approach 1:
Multiple cooling openings are distributed around the fastening web's circumference, ensuring that cooling air reaches all high-stress regions of the transition area. This segmented cooling arrangement provides uniform temperature reduction across the entire fastening web, preventing localized overheating that would occur with a single cooling opening in the annular shoulder.
Solution Approach 2:
Cooling openings are positioned at specific locations on the fastening web where thermal stresses are most severe, ensuring targeted cooling of critical areas. This local cooling strategy effectively reduces thermal stresses throughout the transition area without creating cold spots or leaving regions inadequately cooled.
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 configuration significantly increases the number of cracking load cycles, reducing maintenance needs and extending service life by effectively managing thermal stresses and improving cooling efficiency.
Implementation Method 1
This is cooled by compressed ambient air being conducted through a cooling channel that is defined between the shaft protective jacket and the housing inner wall of the hot gas-carrying housing
Implementation Method 2
The slots, which according to the invention are preferably produced by means of water jet cutting, act as relief cuts and compensate for thermally induced stresses in the transition area between the inner wall of the housing and the fastening web
Implementation Method 3
the slots, which according to the invention are preferably produced by means of water jet cutting
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
The invention relates to a hot gas-conducting casing (7) comprising a hot gas duct (8) of annular cross section, wherein the hot gas duct (8) is bounded inwardly by a casing inner wall (9) and outwardly by a casing outer wall (10) provided with at least one hot gas inlet opening (11), is closed at its end by a casing end wall (12) that connects the casing inner wall (9) and the casing outer wall (10) to one another, and has at its other end an annular hot gas outlet opening (13), wherein an annular attachment web (14; 43) projects radially inward from the casing inner wall (9), wherein the attachment web (14; 43) is provided along its periphery with multiple slots (15; 30; 34; 39; 44) that pass through the attachment web (14; 43) in the axial direction and each have at least one first slot section (16; 31; 35; 40) which extends outward proceeding from the free end of the attachment web (14; 43). The invention further relates to a gas turbine plant (1) having such a hot gas-conducting casing (7).