CMC Turbojet Nozzle Flaps Spherical Hinge Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of ceramic-matrix composite material (CMC) flaps in turbojet exhaust nozzles results in large leakage sections at the joins due to their thicker structure and differential thermal expansion, reducing thrust and posing sealing challenges.
Innovation Solution
The design integrates CMC flaps with integral bearing, sealing, and pivot hinge means, eliminating leakage by forming each flap as a single piece with spherical-joint hinges and convex cylindrical surfaces for reduced wear and improved sealing, and optionally using an anti-abrasion coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CMC material flaps are used to withstand high temperatures and reduce weight, then temperature resistance and weight reduction are improved, but leakage sections at flap joins increase due to thicker structure and large radius of curvature
Solution Approach 1:
The patent applies spheroidality by forming the upstream ends of CMC flaps with spherical portions that pivot on adjacent flaps. This spherical geometry allows the thick CMC material to achieve the necessary small radius of curvature at the join zones, thereby reducing leakage sections while maintaining the material's inherent temperature resistance and weight benefits.
2Temperature
If CMC material flaps are used to withstand high temperatures and reduce weight, then temperature resistance and weight reduction are improved, but sealing complexity increases due to differential thermal expansion with metal gaskets
Solution Approach 1:
The patent applies homogeneity by making both the flap body and the bearing means at its upstream end from the same CMC material. This eliminates the differential thermal expansion problem that would occur with metal portions, simplifying the sealing system while maintaining temperature resistance and weight reduction benefits.
Solution Approach 2:
The patent merges the bearing means and sealing functions directly into the CMC flap structure itself, eliminating the need for separate metal components. The upstream end of each CMC flap is formed integrally with bearing surfaces and spherical hinge portions, combining multiple functions into a single homogeneous material structure.
3Loss of substance
If integral bearing and hinge means are added to CMC flaps to reduce leakage, then gas leakage is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent merges the bearing means, sealing surfaces, and hinge portions into a single integral CMC flap structure. This consolidation reduces the total number of parts and assembly steps compared to using separate metal components, thereby reducing manufacturing complexity while achieving the leakage reduction goal.
Solution Approach 2:
The patent uses CMC composite material with tailored fiber orientation and layer structure to achieve the complex three-dimensional geometry of the upstream end, including spherical hinge portions and bearing surfaces. This allows complex shapes to be manufactured as single pieces using composite material forming techniques, reducing assembly complexity.
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 reduces gas leakage and wear, maintaining thrust while minimizing the number of parts and weight, ensuring effective sealing and longevity of the nozzle components.
Implementation Method 1
each flap is also made integrally with hinge means pivotally connected to the upstream ends of the adjacent flaps. This makes it possible to reduce the leakage sections at the joins between the adjacent flaps
Implementation Method 2
the upstream end of each flap includes a circularly-cylindrical portion that is oriented transversely relative to the axis of the exhaust-nozzle, and tangentially relative to the peripheral gasket, and having a convex cylindrical surface that bears against the peripheral gasket
Implementation Method 3
the flaps may be coated at least part in an anti-abrasion coating at their upstream ends and along their longitudinal edges
Data Source
AI summary
A convergent turbojet exhaust nozzle comprising a ring of hinged flaps made up of controlled flaps and of follower flaps disposed in alternation and co-operating at their upstream ends with a peripheral sealing gasket arranged at the outlet from an afterburner channel, each flap being made out of a ceramic-matrix composite material, and at its upstream end, each flap being made integrally with bearing means for bearing against the above-mentioned peripheral gasket, and with spherical-joint means between their upstream ends.