Variable Ejection Nozzle Longitudinal Translation
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Solution Overview
Problem
Civil turbomachine nozzles with fixed ejection sections operate inefficiently at varying speeds, such as during take-off, ascent, descent, and idle modes, due to geometric constraints and high manufacturing costs, making it difficult to implement variable-section nozzles.
Innovation Solution
A gas ejection nozzle with a geometrically variable neck section achieved through longitudinal translation of the primary cowl, allowing precise adjustment of the ejection section based on engine speeds, using a movable secondary cowl with decreasing internal diameter and patterns to reduce drag and acoustic emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed ejection section nozzle is used, then the manufacturing cost is reduced and the structure is simplified, but the nozzle operates in a degraded manner at high and low operating speeds
Solution Approach 1:
The patent applies the dynamics principle by making the secondary cowl movable rather than fixed. The secondary cowl can translate longitudinally between a retracted position (for high speed operation) and an extended position (for low speed operation), allowing the nozzle to adapt its ejection section geometry dynamically based on operating conditions. This resolves the contradiction by enabling variable geometry without the complexity of flaps, achieving both cost-effectiveness and operational efficiency across different speed regimes.
2Adaptability or versatility
If flaps are arranged in the extension of the downstream end of the nozzle to vary the ejection section, then the nozzle can adapt to different operating speeds, but the device complexity increases and manufacturing cost rises
Solution Approach 1:
The patent replaces complex flap mechanisms with a simpler movable secondary cowl that translates longitudinally. This dynamic structure allows the ejection section to vary continuously without requiring articulated flaps, hinges, or complex actuation systems. The movable cowl is guided by rails or tracks, providing a robust yet simple implementation that achieves adaptability while minimizing device complexity.
Solution Approach 2:
The nozzle is segmented into a fixed primary cowl and a movable secondary cowl, allowing independent optimization of each section. The primary cowl maintains the basic nozzle geometry while the secondary cowl provides variable area adjustment. This segmentation enables the variable geometry function to be isolated to a specific component, simplifying the overall design and reducing manufacturing costs compared to integrating variable geometry throughout the entire nozzle structure.
3Adaptability or versatility
If flaps are used to reduce or increase the ejection section, then the nozzle can optimize performance at different speeds, but the installation constraints related to nacelle and wing integration are violated
Solution Approach 1:
The movable secondary cowl translates along the longitudinal axis of the nozzle, moving in-line with the existing nozzle geometry rather than extending downstream beyond the nacelle trailing edge. This longitudinal motion pattern respects the aerodynamic contours of the nacelle and wing integration, avoiding interference with ground clearance and trailing edge shape constraints while still providing variable ejection section capability.
4Adaptability or versatility
If a movable secondary cowl is introduced to vary the ejection section, then the nozzle can adapt to different operating speeds, but the mass of the nozzle increases
Solution Approach 1:
The nozzle is divided into a heavy fixed primary cowl and a lightweight movable secondary cowl. The secondary cowl, which provides the variable area function, is designed to be as light as possible while maintaining structural integrity during translation. This segmentation allows the majority of the nozzle mass to remain stationary and optimized for strength, while only a small movable portion adds the necessary weight for actuation, minimizing the overall mass penalty.
Solution Approach 2:
The movable secondary cowl is designed to be a simplified copy or subset of the full nozzle structure. Rather than duplicating the entire complex primary cowl geometry, the secondary cowl replicates only the essential aerodynamic contours needed for variable area control. This reduces material usage and mass while maintaining the necessary aerodynamic function across different positions.
Data Source
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AI summary
The invention relates to an ejection nozzle (32) for a double-flow turbomachine, comprising a central body (34), a primary hood (36) surrounding the central body to delimit a primary channel (38), and a secondary hood (40) surrounding the primary hood to delimit a secondary channel (42), the secondary hood (40) consisting of a fixed part (48) and a movable part (50) disposed in the extension of the fixed part and able to move longitudinally upstream and downstream relative to the fixed part and relative to the primary hood so as to vary the ejection and/or throat section of the nozzle, the fixed part (48) of the secondary hood having a plurality of spaced repeating patterns disposed in the extension of its trailing edge, and the movable part (50) of the secondary hood having on its external surface a plurality of impressions of shapes complementary to the patterns of the fixed part.