Convergent Divergent Nozzle Cooling via Plenum and Telescopic Pipelines
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Solution Overview
Problem
Existing ventilation systems for turbojets face challenges in efficiently and uniformly cooling divergent flaps due to direct air tapping from the annular duct, which disrupts operation and makes it difficult to integrate cooling devices within the cluttered nozzle environment, leading to poor cooling of convergent flaps and potential reintroduction of hot gases.
Innovation Solution
An annular plenum chamber and distribution cells linked by telescopic pipelines provide pressurized cooling air to divergent flaps, with adjustable flow rate control using a movable ring, ensuring uniform pressure and flow distribution without pressure reductions or hot gas reintroduction, and allowing for efficient cooling of both convergent and divergent flaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If direct air tapping from the annular duct is used to cool divergent flaps, then cooling is provided, but it disrupts the ventilation operation and causes hot gas reintroduction
Solution Approach 1:
The cooling system is segmented into separate functional components: an annular plenum chamber for air accumulation and pressure equalization, distribution cells for uniform flow allocation, and individual telescopic pipelines for each flap. This segmentation isolates the cooling function from the main ventilation flow, preventing disruption and hot gas reintroduction while maintaining effective cooling.
Solution Approach 2:
The annular plenum chamber acts as an intermediary between the cooling air source and the divergent flaps. It receives cooling air from the annular duct, equalizes pressure across all outlets, and distributes air uniformly through distribution cells, thereby mediating between the cooling requirement and the ventilation system to prevent operational disruption.
2Volume of moving object
If cooling devices are integrated within the nozzle, then space utilization is improved, but the cluttered environment with jacks and levers makes integration difficult
Solution Approach 1:
The conical shell structure serves multiple functions: it forms the structural framework of the nozzle, provides mounting surfaces for distribution cells, acts as a boundary for the plenum chamber, and integrates with existing control mechanisms. This multi-functionality reduces the need for additional separate components, simplifying integration despite the cluttered environment.
Solution Approach 2:
The cooling system components are nested within the existing nozzle structure: the plenum chamber is formed by the conical shell and boundary wall, distribution cells are positioned within the annular space, and telescopic pipelines extend to individual flaps. This nested arrangement maximizes space utilization while minimizing additional footprint in the cluttered nozzle environment.
3Temperature
If uniform cooling of all flaps is achieved, then cooling effectiveness is improved, but it requires complex distribution mechanisms
Solution Approach 1:
The annular plenum chamber creates an equipotential pressure distribution for cooling air before it reaches the distribution cells. By ensuring uniform pressure across all outlet locations in the plenum chamber, the system achieves uniform cooling flow to all divergent flaps without requiring complex active control mechanisms, as the pressure equalization occurs passively through the plenum chamber geometry.
4Adaptability or versatility
If adjustable flow rate control is added, then adaptability to engine conditions is improved, but the system complexity increases
Solution Approach 1:
The system incorporates adjustable flow rate control through the distribution cells and telescopic pipelines, allowing dynamic adaptation to different engine operating conditions. The control mechanism enables variable cooling flow distribution while maintaining the overall simplicity of the passive plenum chamber design, balancing adaptability with system complexity.
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 ensures efficient, uniform cooling of divergent and convergent flaps, preventing pressure reductions and hot gas reintroduction, while allowing for adaptable flow rates to suit engine conditions, enhancing operational performance and reducing the infrared signature.
Implementation Method 1
The plenum chamber makes it possible to slow the speed of the air received and to increase the pressure of the air for cooling the follower divergent flaps
Implementation Method 2
telescopic pipelines each linking a cell to the follower divergent flap situated in the same plane of symmetry as said cell
Implementation Method 3
fed with cooling air through drillings made in a boundary wall between said plenum chamber and the downstream end of said annular passage
Data Source
AI summary
The invention relates to a ventilation system for a convergent divergent exhaust nozzle in a bypass turbojet comprising an afterburn chamber surrounded by an annular passage through which circulates a stream of cooling air, a convergent divergent axisymmetric nozzle arranged downstream of said afterburn chamber, each circle of flaps comprising alternately a plurality of controlled flaps, and a plurality of follower flaps, a circle of cold flaps arranged radially outside said nozzle and hinged at their upstream end to a conical shell linked to the downstream part of the casing. The means of cooling the divergent flaps comprise an annular plenum chamber delimited downstream by said conical shell and fed with cooling air through drillings made in a boundary wall between said plenum chamber and the downstream end of said annular passage, a plurality of distribution cells surrounding the plenum chamber and linked to the latter, said cells being delimited downstream by said conical shell and being arranged around the X axis in the planes of symmetry of the follower flaps and telescopic pipelines each linking a cell to the follower divergent flap situated in the same plane of symmetry as said cell.