Aircraft Propulsion Unit D-Shaped Nacelle Assembly Box
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Solution Overview
Problem
The existing nacelle designs for aircraft turbojet engines, particularly those with D-shaped structures, face challenges in accessing the turbojet engine for maintenance due to complex configurations and interference issues with cascade vane rails, leading to increased time and complexity during maintenance operations.
Innovation Solution
A propulsion unit with a D-shaped structure nacelle that incorporates movable cascade vanes with extended six o'clock rails downstream of the fan casing, along with an assembly box and locking device, allowing for continuous force passage and reduced nacelle length, thereby simplifying maintenance access and reducing mass and drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If D-shaped structure nacelle with extended six o'clock rails is used, then maintenance access is facilitated and nacelle length is reduced, but cascade vane rail interference and structural complexity increase
Solution Approach 1:
The nacelle is divided into two D-shaped half-structures (117a, 117b) that can be separated from each other. This segmentation allows maintenance personnel to access the turbojet engine by separating the half-structures, facilitating easier maintenance while managing the complexity of the extended rails through modular construction.
Solution Approach 2:
The cascade vanes are enabled to move in the longitudinal direction (six o'clock position) in addition to their traditional radial movement. This dimensional change allows the cascade vanes to clear interference with the extended rails during maintenance access operations, resolving the contradiction between improved maintenance access and rail interference.
2Length of moving object
If cascade vanes are made movable in longitudinal direction, then continuous force passage is provided and nacelle length is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The longitudinal movement capability is merged with the existing radial movement mechanism of the cascade vanes. By combining these movement modes into a single integrated system, the patent achieves continuous force passage and reduced nacelle length while avoiding the need for completely separate movement mechanisms, thereby simplifying manufacturing.
Solution Approach 2:
The cascade vane system is designed to perform multiple functions: radial movement for thrust reversal operation and longitudinal movement for maintenance access and force passage continuity. This multi-functionality allows the same structure to achieve both shortened nacelle length and continuous force transmission without requiring additional dedicated components.
3Ease of repair
If two D-shaped half-structures are used instead of integral annular outer cowl, then maintenance access is improved, but structural complexity and number of parts increase
Solution Approach 1:
The integral annular outer cowl is segmented into two D-shaped half-structures (117a, 117b) that can be separated from each other. This segmentation directly improves engine accessibility by allowing the half-structures to be moved apart for maintenance, while the modular nature of the segmentation keeps the increase in structural complexity manageable through standardized connection interfaces.
Data Source
AI summary
A propulsion unit for an aircraft including a nacelle with a D-shaped structure housing a thrust-reversing device with movable vanes, the nacelle containing two D-shaped half-structures each including an external reverser half-cowl. The propulsion unit contains an assembly box-type structure, attached in downstream cantilevered fashion to the turbojet engine fan casing, the box-type structure including two guide rails guiding the deflection vanes, a locking device between the assembly box-type structure and the half-beams in the six o'clock position of the D-shaped half-structures, the assembly box-type structure being arranged in the propulsion unit such that the guide rails guiding the vanes of the assembly box-type structure are situated in the continuation of the guide rails in the six o'clock position guiding the vanes attached to the fan casing, to provide continuity between the rails.