Movable Support Mast Fairing for Thrust Reverser Clearance
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Solution Overview
Problem
The interference between the support mast and the movable cowl of a turbojet engine's nacelle during thrust reverser operation generates parasitic drag, vibrations, and mechanical stresses, which are not adequately addressed by existing designs.
Innovation Solution
A support mast with a movable fairing connected via hinged connecting rods and a slide, allowing synchronized movement with the nacelle's movable cowl, and incorporating preload springs and locators to maintain clearance and centering, along with an aerodynamic barrier to manage dynamic pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the support mast is configured with a fixed fairing, then the structural simplicity is maintained, but parasitic drag and mechanical stresses increase during thrust reverser operation
Solution Approach 1:
The fairing is transformed from a fixed structure to a movable one that can dynamically adjust its position. The fairing is configured to move between a retracted position (during thrust reverser operation) and an extended position (during normal flight), allowing it to adapt to different operational states and eliminate parasitic drag generated by interference with the movable cowl.
Solution Approach 2:
The support mast is divided into distinct functional components: a fixed portion providing structural support and a movable fairing portion that can independently adjust its position. This segmentation allows the fairing to move relative to the fixed mast structure, resolving the conflict between structural simplicity and aerodynamic performance.
2Ease of operation
If the movable fairing is rigidly connected to the nacelle, then the movement synchronization is improved, but mechanical stresses and vibrations increase
Solution Approach 1:
A connecting rod mechanism serves as an intermediary between the movable cowl and the movable fairing. This mechanical linkage transmits the movement of the cowl to the fairing in a controlled manner, ensuring synchronization while distributing and reducing mechanical stresses compared to a rigid direct connection.
Solution Approach 2:
The connecting mechanism employs a composite structure combining rigid elements (connecting rods, ball joints) with controlled clearance design. The ball joints provide rotational freedom while the controlled clearances allow for thermal expansion and stress relief, creating a composite mechanical system that balances rigidity and flexibility.
3Adaptability or versatility
If clearance between the movable fairing and fixed elements is increased, then the adjustment freedom is improved, but parasitic drag increases in closed position
Solution Approach 1:
The clearance between the movable fairing and fixed elements is not fixed but dynamically adjusted through the connecting rod mechanism. During operation, the mechanism allows sufficient clearance for free adjustment and movement. In the closed position, the mechanism ensures the fairing aligns closely with the fixed elements to minimize clearance and reduce parasitic drag.
Solution Approach 2:
The spatial parameters (clearance, position, orientation) of the movable fairing are dynamically changed based on operational requirements. The connecting rod mechanism transforms the movement of the cowl into corresponding movements of the fairing, adjusting its position parameter to achieve optimal clearance during operation and minimal clearance during closed position.
4Manufacturing precision
If preload springs are added to maintain clearance, then the alignment precision is improved, but device complexity increases
Solution Approach 1:
Preload springs are incorporated into the connecting rod mechanism to provide beforehand cushioning and maintain optimal clearance between the movable fairing and fixed elements. The springs are pre-loaded to ensure consistent alignment and prevent excessive clearance or contact stresses, improving alignment precision while using a simple elastic element rather than complex adjustment mechanisms.
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 ensures minimal interference and reduces parasitic drag, vibrations, and mechanical stresses by facilitating synchronized movement and maintaining proper alignment, enhancing operational efficiency and reducing environmental impact.
Implementation Method 1
one or more connecting rods, each hinged on a ball joint at each end, to connect the movable fairing of the mast to the movable cowl of the nacelle
Implementation Method 2
incorporating preload springs and locators to maintain clearance and centering
Implementation Method 3
along with an aerodynamic barrier to manage dynamic pressures
Data Source
AI summary
Support mast for a turbojet engine including a movable fairing extending from a trailing edge and a distal end of the mast and configured to move, in the axial direction, together with a movable cowl of a nacelle of the turbojet engine, between a closed position and an open position, and one or more connecting rods, each hinged on a ball joint at each end, to connect the movable fairing of the mast to the movable cowl of the nacelle.