Labyrinth Seal Teeth Reduce Gas Turbine Thrust Reverser Leakage
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Solution Overview
Problem
Gas turbine engine thrust reversers experience leakage of fan bypass flow due to large components subject to air loads, vibration, and thermal gradients, leading to mixing pressure loss and increased specific fuel consumption (SFC).
Innovation Solution
A transcowl design with an arcuate outer and inner wall, an arcuate baffle, and a labyrinth seal configuration, including forward seals with axially-extending teeth and circumferential restrictors, to minimize air leakage by creating a tortuous flow path and blocking air movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thrust reverser components are made large to handle air loads and vibration, then structural strength is improved, but air leakage increases
Solution Approach 1:
The seal arrangement divides the sealing function into multiple components: forward seals with seal teeth on the inner wall, aft seals with seal teeth on the torque box, and a baffle seal. This segmentation allows each component to contribute to sealing while maintaining structural integrity of the overall large reverser assembly.
Solution Approach 2:
The patent introduces seal teeth as intermediary elements that create a labyrinthine path between the bypass duct and secondary flowpaths. These teeth act as mediators that physically obstruct air leakage while allowing the large reverser components to maintain their structural dimensions.
2Loss of energy
If gaps and tolerances are reduced to minimize leakage, then air leakage is reduced, but manufacturing precision requirements increase
Solution Approach 1:
Instead of relying solely on reducing gap size in one dimension, the patent creates a multi-dimensional labyrinthine path using seal teeth that extend axially from surfaces. The air must navigate around multiple teeth in sequence, effectively increasing the sealing path length without requiring tighter tolerances on individual component gaps.
Solution Approach 2:
The seal teeth are positioned and configured in advance to create predetermined flow restriction zones. The labyrinth seal geometry is designed beforehand to force air through specific tortuous paths, allowing standard manufacturing tolerances to achieve the desired leakage reduction.
3Loss of energy
If seal complexity is increased to reduce leakage, then air leakage is reduced, but device complexity increases
Solution Approach 1:
The seal arrangement nests multiple sealing functions within the existing reverser structure. The forward seals, aft seals, and baffle seal work together in a nested configuration where each seal component is integrated into the overall reverser assembly, reducing the need for separate complex sealing 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 solution reduces unwanted air leakage, thereby improving the engine's net thrust and lowering specific fuel consumption by approximately 0.05% in certain applications.
Implementation Method 1
The forward seal includes a plurality of axially-extending, radially spaced-apart arcuate seal teeth which collectively define a labyrinth seal
Implementation Method 2
At least one restrictor is disposed in the interior area so as to block air movement in a circumferential direction within the interior area
Data Source
AI summary
A transcowl for a gas turbine engine thrust reverser includes an arcuate outer wall; an arcuate inner wall; and an arcuate baffle positioned between the inner and outer walls at a forward end of the transcowl. The baffle has an arcuate cross-sectional shape which defines a forward-facing interior area. An arcuate forward seal is carried at a forward end of the inner wall. The forward seal includes a plurality of axially-extending, spaced-apart arcuate seal teeth which collectively define a labyrinth seal.