Active Flow Control Thrust Reverser Boundary Layer Attachment
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Solution Overview
Problem
Thrust-reverser assemblies in jet engines face challenges in maintaining boundary layer attachment to bullnose fairings during reverse-thrust configurations, especially at higher flow speeds, which restricts the size and placement of the engine due to separation issues.
Innovation Solution
Incorporating an active flow-control device that injects a flow-control fluid stream into the boundary layer adjacent to the bullnose fairing, using a vortex generator or suction assembly to resist separation, allowing for attachment over a wide range of flow speeds and smaller radii of curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bullnose fairing uses a conventional large radius of curvature to prevent boundary layer separation, then boundary layer attachment is maintained, but the engine size and weight increase
Solution Approach 1:
The patent applies pneumatic flow control by injecting a fluid stream (bled air or synthetic jet) through injection orifices in the bullnose fairing. This fluid injection energizes the boundary layer, preventing separation and allowing the use of smaller radius of curvature fairings, thereby reducing engine weight while maintaining reliable boundary layer attachment
Solution Approach 2:
The patent changes the physical state and parameters of the boundary layer by injecting high-velocity fluid streams that modify the boundary layer's energy and velocity profile. This parameter change allows the boundary layer to remain attached to fairings with smaller radii of curvature, enabling weight reduction
2Reliability
If the bullnose fairing uses a conventional large radius of curvature to prevent boundary layer separation, then boundary layer attachment is maintained, but the engine placement flexibility decreases
Solution Approach 1:
The pneumatic flow control system enables the use of compact fairing designs with smaller radii of curvature, which in turn allows for more flexible engine placement options within the aircraft fuselage while maintaining boundary layer attachment through active fluid injection
3Reliability
If the bullnose fairing uses a conventional large radius of curvature to prevent boundary layer separation, then boundary layer attachment is maintained, but the bypass ratio is limited
Solution Approach 1:
By using pneumatic flow control to maintain boundary layer attachment on compact fairings, the patent enables larger bypass duct cross-sections and higher bypass ratios, increasing the quantity of bypass stream while preventing separation through active fluid injection
4Weight of stationary object
If active flow-control is used to enable smaller radius of curvature, then engine weight is reduced, but device complexity increases
Solution Approach 1:
The flow control system uses bled air from the engine's own operation to provide the injection stream, making the system self-sufficient. The synthetic jet generator option also eliminates the need for external compressors or pumps, reducing system complexity while achieving weight reduction through compact fairing design
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 solution enables boundary layer attachment at higher flow speeds and smaller radii, reducing engine size and weight, increasing flexibility in engine placement and improving fuel efficiency by preventing separation and allowing for larger bypass ratios.
Implementation Method 1
energize a boundary layer fluid flow within a boundary layer that is adjacent to the bullnose fairing
Implementation Method 2
resist separation of the boundary layer from the bullnose fairing
Implementation Method 3
the active flow-control device includes a vortex generator that is configured to generate a vortex within the boundary layer
Implementation Method 4
the active flow-control device includes a suction assembly that is configured to remove a suction stream from the boundary layer
Implementation Method 5
the flow-control fluid stream includes a compressed gas stream that is generated by the jet engine
Data Source
Figure 1
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Figure 4~5
AI summary
Thrust-reverser assemblies (60) that utilize active flow-control and systems and methods (200) including the same are disclosed herein. The thrust-reverser assemblies define a forward-thrust configuration (62) and a reverse-thrust configuration (64). The thrust-reverser assemblies include a bullnose fairing (100) that defines a portion of a reverser duct (66) and an active flow-control device (150). The active flow-control device is located to energize a boundary layer fluid flow (82) within a boundary layer (80) that is adjacent to the bullnose fairing to resist separation of the boundary layer from the bullnose fairing when the thrust-reverser assembly is in the reverse-thrust configuration. The methods include flowing (210) a thrust-reverser fluid stream through the reverser duct to generate the boundary layer and energizing (220) a boundary layer fluid flow within the boundary layer with an active flow-control device to resist separation of the boundary layer from the bullnose fairing.