Air Inlet Rectifier Vanes for Turbojet Thrust Reversal
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Solution Overview
Problem
Turbojet engines with high bypass ratios face challenges in thrust reversal due to the inefficiency of conventional systems, which result in reduced performance and increased mass, bulk, and drag, especially during landing, where the reverse air flow is twisted and bypasses the aerodynamic profile, creating a local depression that opposes the reverse thrust.
Innovation Solution
Deployment of rectifier vanes that straighten the reverse air flow to align it axially, promoting optimal thrust reversal by eliminating the formation of depressions and enhancing separation at the air inlet lip, similar to OGV blades, while maintaining aerodynamic profiles during thrust phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional thrust reversal system is integrated into the nacelle, then the aircraft's braking distance is reduced, but the mass, size and drag of the turbojet are significantly increased
Solution Approach 1:
The fan blades are designed to perform dual functions: during normal operation they generate forward thrust by accelerating airflow downstream, and during thrust reversal they redirect airflow upstream to create reverse thrust. This eliminates the need for separate thrust reversal mechanisms, reducing mass and complexity while maintaining effective braking capability
Solution Approach 2:
The fan blade pitch angle is made variable, allowing dynamic adjustment between different operational modes. By changing the pitch angle, the fan can efficiently switch between forward thrust generation and reverse thrust generation, providing adaptability for different flight phases without requiring additional mechanical systems
2Weight of moving object
If a variable pitch fan is used to enable thrust reversal, then the system mass is reduced, but the reverse airflow is twisted azimuthally reducing thrust reversal performance
Solution Approach 1:
Rectifier vanes are introduced as intermediary elements between the fan and the air inlet. These vanes straighten the twisted reverse airflow generated by the rotating fan, converting the azimuthally twisted flow into axial flow that effectively opposes the incoming airflow, thereby restoring thrust reversal performance
Solution Approach 2:
The rectifier vanes are positioned specifically in the region where the twisted flow occurs, applying flow straightening only where needed. This localized intervention corrects the airflow distortion without interfering with the overall fan operation or requiring modification of the entire propulsion system
3Productivity
If rectifier vanes are deployed to straighten reverse airflow, then thrust reversal performance is improved, but the device complexity increases
Solution Approach 1:
The rectifier vanes are designed to be movable rather than fixed, allowing them to be deployed only when thrust reversal is required. During normal operation, the vanes remain retracted, maintaining simple aerodynamic profiles. This dynamic configuration reduces complexity by eliminating the need for permanently complex structures
Solution Approach 2:
The rectifier vane system is divided into multiple independent vanes that can be controlled separately or in groups. This segmentation allows for simplified control mechanisms and reduces the complexity of any single moving component while achieving the overall flow straightening objective
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 improves the performance of thrust reversal by ensuring the reverse air flow opposes the axial airflow directly, increasing thrust efficiency without affecting regular thrust performance and reducing the weight and drag of the turbojet engine.
Implementation Method 1
Deployment of rectifier vanes that straighten the reverse air flow to align it axially, promoting optimal thrust reversal by eliminating the formation of depressions
Implementation Method 2
The air inlet 200 has an aerodynamic profile that allows the separation of an upstream airflow F into the inner airflow F-INT guided by the inner wall 201 and an outer airflow F-EXT guided by the outer wall 202
Implementation Method 3
a fan 101 mounted to rotate around the axis X in order to accelerate, during the thrust of the turbojet engine 100, an airflow circulating from upstream to downstream within the turbojet engine 100
Data Source
Figure 1~2
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AI summary
Disclosed is a method for using an aircraft turbojet engine (1) comprising an air inlet (2) comprising a plurality of rectifier vanes (3), each rectifier vane (3) being mounted such that it can move between a retracted position to assist the thrust phase and a deployed position (B) in which the rectifier vane (3) protrudes from the inner wall (21) in a radially inward direction in order to rectify the reverse air flow (F-INV) of the inner wall (21) to assist a thrust-reverse phase, in which method at least one rectifier vane (3) is in the retracted position during a turbojet engine thrust phase (1), the method comprising, during a thrust-reverse phase of the turbojet engine (1), a step of moving the rectifier vane (3) to the deployed position.