Pinned CMC Combustor Heat Shield for Thermal Expansion Relief
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Solution Overview
Problem
Conventional heat shields in turbine engines face challenges due to exposure to high temperatures, leading to material degradation and potential mechanical stress from disparate thermal expansion of metallic and ceramic materials, which complicates their assembly and maintenance.
Innovation Solution
A heat shield design with a metallic dome and CMC heat shield assembly connected by pinned assemblies, allowing for differential thermal expansion and contraction, and incorporating seals to manage cooling air flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat shield is made of composite material and mounted to a metallic structural component, then thermal protection is achieved, but mechanical stress increases due to disparate thermal expansion
Solution Approach 1:
The heat shield is divided into a first portion made of composite material and a second portion made of metallic material, allowing each segment to expand and contract independently according to its material properties, thereby reducing mechanical stress at the junction
Solution Approach 2:
The heat shield utilizes composite materials in the first portion to provide thermal protection, while combining this with metallic material in the second portion to accommodate thermal expansion differences and reduce mechanical stress
2Stability of the object's composition
If rigid connection is used between heat shield and dome, then structural stability is improved, but thermal expansion stress increases
Solution Approach 1:
The connection between the heat shield and dome is designed to be dynamic rather than rigid, allowing the heat shield to move and expand freely in response to thermal changes while maintaining structural stability during operation
Solution Approach 2:
By segmenting the heat shield into different material portions, the structure can maintain stability through the metallic portion while the composite portion accommodates thermal expansion independently
3Temperature
If complex mounting structure is used for heat shield, then thermal protection is improved, but ease of maintenance deteriorates
Solution Approach 1:
The heat shield is segmented into distinct portions that can be independently replaced, and the simplified mounting structure allows for easy removal and installation during maintenance without requiring complex disassembly procedures
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
Enhances durability and reduces mechanical stress by accommodating thermal expansion, while maintaining effective cooling and facilitating easy replacement of the heat shield.
Implementation Method 1
the heat shield and the dome undergo thermal expansion and contraction, with the pin end sliding in the hole
Implementation Method 2
a seal... between the dome inner portion and the heat shield inner portion, for maintaining concentricity
Implementation Method 3
the heat shield... thermally protecting the dome face portion from heat from the combustion
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A combustor (86) of a turbine engine (10) combusts fuel and air (58). The combustor (86) includes a dome (302) and a heat shield (128, 304, 604) fastened to the dome. The heat shield (128, 304, 604) is unconstrained relative to dome (302), to permit relative thermal expansion and contraction in a radial direction. A heat shield inner portion (314, 614) is generally annular in shape, is arranged about the combustor longitudinal centerline axis, is smaller in diameter than a dome inner portion (308), and is assembled inside of the dome inner portion (308). A plurality of pinned assemblies (306, 606) fastens the heat shield (128, 304, 604) to the dome (302). Each pinned assembly (306, 606) includes a fastener (320) with a pin end (324), the pin end (324) assembled in a clearance fit into a hole (330, 630) in the heat shield inner portion (314, 614). The fastener (320) is fixed to the dome inner portion (308), the pin end (324) sliding in the hole (330, 630) in the heat shield (128, 304, 604) during relative thermal expansion and contraction between the dome (302) and the heat shield (128, 304, 604).