Combustor Skin Assembly Sliding Flange Thermal Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing reverse flow combustor designs for gas turbine engines face challenges in managing stress in the cold skin due to thermal growth mismatch with the hot skin, leading to potential cracking and increased weight or cost, particularly in aircraft applications.
Innovation Solution
A combustor skin assembly featuring a sliding engagement between a male flange of the cold skin and a female recess of the receiving skin, allowing for thermal growth accommodation without welding at both ends, thereby reducing internal mechanical stress and weight while maintaining an air-tight seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding is used at both ends of the cold skin to achieve air-tight connection, then the connection reliability is improved, but the cold skin is exposed to high stress from thermal growth mismatch which leads to premature cracking and increased weight
Solution Approach 1:
The connection structure is segmented into two distinct types: a welded securing portion at one end providing air-tight connection, and a sliding flange connection at the other end accommodating thermal growth. This segmentation allows each connection type to perform its specialized function without compromising the overall system.
Solution Approach 2:
The connection system transitions from a static rigid welded structure to a dynamic system where one end allows sliding movement. The male flange on the cold skin slides within the female recess on the hot skin, enabling the cold skin to dynamically adjust to thermal growth while maintaining connection.
2Strength
If the cold skin is made relatively long to accommodate thermal growth stress, then the stress threshold is maintained, but the weight increases which is undesired in aircraft applications
Solution Approach 1:
The sliding flange connection introduces dynamic capability to the cold skin assembly, allowing it to accommodate thermal growth through controlled sliding movement rather than requiring excessive length for stress absorption. This reduces the cold skin length and corresponding weight while maintaining stress management.
Solution Approach 2:
The connection system changes the physical state of the cold skin from a statically constrained component to one with controlled movement capability. By allowing sliding in the flange connection, the system changes the boundary conditions to accommodate thermal expansion without increasing dimensions or weight.
3Strength
If welding at one end and sliding forged ring assembly at the other end is used to achieve connection, then the stress management is improved, but significant costs are added in addition to weight
Solution Approach 1:
Both the cold skin and receiving skin are formed from the same material - sheet metal - and both are attached using the same welding process. This homogeneity in material selection and manufacturing method reduces complexity and cost compared to using specialized forged ring assemblies.
Solution Approach 2:
The sliding flange connection uses simple sheet metal components that are easier and less expensive to manufacture than forged ring assemblies. The male flange and female recess are formed directly from sheet metal, eliminating the need for complex forging processes and reducing overall manufacturing cost.
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 sliding engagement effectively reduces mechanical stress on the cold skin, extending its lifespan and reducing weight and cost, while maintaining a reliable cooling cavity for heat management in gas turbine engines.
Implementation Method 1
the hot skin being exposed to higher temperature than the cold skin, its thermal growth was greater than that of the cold skin
Implementation Method 2
the cold skin was provided with impingement holes through which cooling air passes to remove heat from the hot skin by convection
Implementation Method 3
the cooling air also passes through effusion holes in the hot skin, creating a protective air film on the hot surface
Data Source
AI summary
A combustor assembly includes a hot skin of a combustion chamber wall having an inner face exposed to the combustion chamber and an opposite outer face, a receiving skin having a securing portion affixed to the hot skin outer face in an air-tight manner and a receiving flange, extending from the securing portion, that is offset from the hot skin outer face to form a female recess, a cold skin having a cold wall portion spaced from the hot skin and forming a cooling cavity therebetween, a securing portion extending from a first end of the cold wall portion affixed to the hot skin outer face in an air-tight manner and a male flange extending from a second end of the cold wall portion opposite the first end, the male flange snugly received in the female recess and forming a sliding engagement therebetween.