CMC Combustion Liner Ply Architecture for Circumferential Stress
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Solution Overview
Problem
Gas turbine engine liners made of ceramic matrix composite (CMC) materials face significant thermal and mechanical stresses, particularly in the circumferential direction, leading to potential cracking and separation of parts due to thermo-mechanical fatigue.
Innovation Solution
The design incorporates a liner with a base portion and a stiffening portion made of CMC material, where the fibers in the plies are aligned to manage these stresses. The stiffening portion has additional plies with fiber directions aligned with the circumferential direction to enhance stress absorption, and the design includes smooth transitions in thickness to minimize crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a liner is made of ceramic matrix composite (CMC) material, then the liner can withstand high temperature and thermal stress, but the liner is susceptible to cracking and separation due to circumferential stresses from thermo-mechanical fatigue
Solution Approach 1:
The liner incorporates a stiffening portion with a different ply configuration than the base portion. The stiffening portion has additional plies with fibers oriented in the circumferential direction (0 degrees) to specifically address the circumferential stress problem in that critical region, while the base portion maintains a balanced configuration for overall structural integrity.
Solution Approach 2:
The liner is constructed from composite CMC material with strategically oriented fiber plies. The combination of different ply orientations (0 degrees for circumferential strength, 90 degrees for axial strength, and 45 degrees for shear resistance) creates a composite structure that simultaneously addresses multiple stress types while maintaining temperature resistance.
2Strength
If additional plies are added to the stiffening portion with fibers aligned in the circumferential direction, then stress absorption is enhanced, but the device complexity increases
Solution Approach 1:
The liner is divided into distinct functional segments: a base portion with a first plurality of plies providing overall structural support, and a stiffening portion with a second plurality of plies providing localized circumferential stress resistance. This segmentation allows each portion to be optimized for its specific function without unnecessarily complicating the entire structure.
Solution Approach 2:
The stiffening portion is strategically positioned and configured with specific ply orientations only where circumferential stresses are most critical, rather than uniformly increasing complexity throughout the entire liner. This localized approach enhances stress absorption where needed while minimizing overall structural complexity.
3Reliability
If the liner has smooth transitions in thickness, then crack formation is minimized, but the manufacturing precision requirements increase
Solution Approach 1:
The liner incorporates smooth, curved transitions in thickness between the base portion and stiffening portion rather than abrupt changes. This curvature approach distributes stress more evenly and prevents stress concentration points that would lead to crack formation, while the specific geometric design provides clear manufacturing guidance.
Solution Approach 2:
The thickness of the liner is gradually changed through the transition portion, creating a smooth gradient between the base and stiffening portions. This parameter change approach minimizes abrupt stress concentrations and reduces crack risk, while the defined transition geometry provides manufacturable specifications.
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 enhanced design effectively distributes and absorbs circumferential stresses, reducing the risk of cracks and improving the mechanical strength and durability of the liner.
Implementation Method 1
the plurality of plies of the stiffening portion of the liner include a set of plies including a first ply having a fiber direction aligned with the circumferential direction, a second ply adjacent to the first ply, the second ply having a fiber direction aligned with the circumferential direction, and a third ply adjacent to the second ply, the third ply having a fiber direction angled away from the circumferential direction
Data Source
AI summary
A liner for a combustion section of a gas turbine engine includes a base portion and a stiffening portion. The base portion includes a plurality of plies of a composite material including a first ply having a fiber direction aligned with a circumferential direction of the liner and a second ply adjacent to the first ply, the second ply having a fiber direction angled away from the circumferential direction. The stiffening portion is disposed on the base portion and includes a plurality of plies of the composite material including a first ply having a fiber direction aligned with the circumferential direction, a second ply adjacent to the first ply the second ply having a fiber direction aligned with the circumferential direction, and a third ply adjacent to the second ply, the third ply having a fiber direction angled away from the circumferential direction.