Multi-Material Turbine Exhaust Flange for Thermal Deflection
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Solution Overview
Problem
Thermal mismatch between components of a gas turbine engine due to rapid temperature changes during transient events leads to thermally-induced stresses, reducing the service life of the turbine case assembly.
Innovation Solution
A turbine exhaust case design with an outer structural flange made of a different material, such as Inconel® 625, and a geometric configuration that includes a ring portion, tubular portion, and annular mounting portion, which accommodates thermal expansion and distributes stress, reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-material design is used for the outer case and flange, then manufacturing is simpler, but thermal mismatch stresses increase during transient events
Solution Approach 1:
The patent applies composite materials by constructing the exhaust case assembly from multiple materials with different thermal expansion properties. The outer case is made of a first material (e.g., nickel-based superalloy) and the flange is made of a second material (e.g., cobalt-based superalloy or stainless steel) with different coefficients of thermal expansion. This composite structure allows each material to be optimized for its specific function: the outer case for high-temperature resistance and the flange for lower thermal expansion, thereby reducing thermal mismatch stresses during transient heating events while maintaining structural integrity.
Solution Approach 2:
The patent applies local quality by making the flange portion of the exhaust case a different material than the outer case. This localized material differentiation addresses the specific thermal stress problem at the flange region, which experiences significant thermal gradient and constraint during transient events. The flange is specifically designed with material properties suited for accommodating thermal expansion differences, while the outer case maintains material properties optimized for high-temperature gas path containment.
2Length of moving object
If the flange is positioned closer to the struts to reduce overall length, then compactness is improved, but stress concentrations increase due to thermal deflection
Solution Approach 1:
The patent applies the intermediary principle by introducing a multi-segmented flange structure consisting of a forward portion, intermediate portion, and aft portion. The intermediate portion acts as a mediator or buffer zone between the forward portion (near the struts) and the aft portion (mounting region). This intermediate section allows for gradual transition and distribution of thermal deflection stresses, preventing stress concentrations that would occur with a direct, short connection between the outer case and mounting flange, while still maintaining overall compactness.
Solution Approach 2:
The patent applies segmentation by dividing the flange into multiple distinct portions: a forward portion extending forward of the struts, an intermediate portion between the struts, and an aft portion for mounting. This segmentation allows each portion to be optimized for its specific function and stress state, with the intermediate portion specifically designed to accommodate thermal deflection and distribute stresses, thereby enabling a compact overall design without sacrificing strength.
3Reliability
If the flange extends further upstream to accommodate thermal expansion, then thermal stress is reduced, but device complexity increases
Solution Approach 1:
The patent applies dynamics by designing the flange with a geometry that naturally accommodates thermal deflection through its structured configuration. The forward portion extending upstream of the struts, combined with the intermediate and aft portions, creates a flexible yet structurally sound form that can dynamically adjust to thermal expansion and contraction during transient events. This dynamic geometric design allows the flange to absorb thermal stresses without requiring additional active compensation mechanisms or complex control systems.
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 design enhances the durability of the turbine exhaust case by absorbing thermal deflection and reducing stress concentrations, thereby improving the service life and allowing for compact engine designs.
Implementation Method 1
The rapid increase in temperature of the parts exposed to the hot combustion gases may cause them to undergo thermal expansion. If these parts are mounted to other components, which do not experience such a rapid increase in temperature, a thermal mismatch may result and may lead to thermally-induced stresses.
Implementation Method 2
A turbine exhaust case design with an outer structural flange made of a different material, such as Inconel® 625, and a geometric configuration that includes a ring portion, tubular portion, and annular mounting portion, which accommodates thermal expansion and distributes stress, reducing stress concentrations.
Data Source
AI summary
A turbine exhaust case has an inner ring structurally connected to an outer ring via a plurality of struts. An outer flange projects outwardly from the outer case. The outer flange is made of a material different from that of the outer case and includes a ring portion having an inner diameter surface joined to an outer diameter surface of the outer case at a first axial location corresponding to a junction of a leading edge of the plurality of struts and the outer case. The outer flange further includes a tubular portion projecting axially from the ring portion to a second axial location disposed upstream of the struts, and an annular mounting portion projecting outwardly from an outer surface of the tubular portion at the second axial location.