Movable Cascade Thrust Reverser for Turbofan Engine
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Solution Overview
Problem
Conventional turbofan engine thrust reversing apparatuses are inefficient due to a 'dead zone' in the forward portion of the cascade assembly, where little airflow is converted into reverse thrust, leading to reduced airflow exit velocity and thrust efficiency.
Innovation Solution
A nacelle assembly with a translatable sleeve and blocker doors that expose a cascade assembly with uniform or non-uniform cross-sections and optional scoops, allowing airflow to be directed more uniformly across the cascade assembly by translating it toward the engine centerline during deployment, creating a larger outlet opening and improving airflow distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional cascade assembly is used for thrust reversal, then reverse thrust can be generated, but the forward portion creates a dead zone with inefficient airflow conversion and reduced thrust efficiency
Solution Approach 1:
The cascade assembly is made movable rather than stationary, allowing it to translate toward the engine centerline during deployment. This dynamic positioning enables the cascade to actively engage the bypass airflow more effectively, eliminating the dead zone in the forward portion and improving airflow conversion efficiency throughout the entire cascade length.
Solution Approach 2:
The cascade assembly's position parameter is changed during operation by translating it toward the engine centerline. This parameter change allows the cascade to optimize its interaction with the bypass airflow, ensuring uniform airflow distribution across all sections and maximizing reverse thrust efficiency while reducing energy loss.
2Force
If the cascade assembly is made longer to increase reverse thrust, then more airflow can be processed, but the device complexity and nacelle space requirements increase
Solution Approach 1:
By making the cascade assembly movable and translating it toward the engine centerline, the effective interaction length with the airflow is increased without physically extending the cascade structure. This dynamic approach allows a compact cascade to process more airflow uniformly, generating sufficient reverse thrust while maintaining a compact design that reduces device complexity and space requirements.
3Force
If blocker doors are deployed to redirect airflow through the cascade, then reverse thrust is generated, but airflow is crowded into a small area resulting in reduced exit velocity
Solution Approach 1:
The movable cascade assembly translates toward the engine centerline to actively expand the airflow passage area. This dynamic expansion prevents airflow crowding by providing sufficient space for the redirected airflow to pass through uniformly, maintaining high exit velocity while still generating effective reverse thrust through the blocker door-cascade system.
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 design enhances reverse thrust efficiency by uniformly distributing airflow across the cascade assembly, reducing pressure drop and allowing for a more efficient conversion of bypass airflow into reverse thrust, potentially shortening the cascade assembly without compromising performance.
Implementation Method 1
Because of the momentum of the bypass airflow in the bypass duct, the majority of the reverse thrust is generated within the aft portion of the conventional cascade assembly
Data Source
AI summary
A nacelle assembly for a turbofan engine includes a forward nacelle portion having an aft edge and defining a bypass duct that transports bypass airflow of the turbofan engine, a translatable sleeve that is translatable aft of the forward nacelle portion and a reverse thrust apparatus that is movable between a stowed position, and a deployed position. When the reverse thrust apparatus is deployed, the translatable sleeve is moved aft to a position away from the aft edge of the forward nacelle portion to expose a cascade assembly comprising an opening in the bypass duct, and one or more blocker doors are deployed so as to extend into the bypass duct, such that at least a portion of the airflow in the bypass duct is directed out the bypass duct through the cascade assembly. Also, during deployment of the reverse thrust apparatus, at least a portion of the cascade assembly translates toward the engine centerline. The cascade assembly may have a cross-section that is non-uniform.