Variable Area Nozzle Cooling With Ejector-Driven Sleeve Airflow
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Solution Overview
Problem
Existing variable area nozzles for aircraft engines require improvements in cooling efficiency and structural design to effectively manage the thermal stresses and pressure differentials encountered during operation.
Innovation Solution
A variable area nozzle design featuring a nozzle sleeve with a shell, liner, cooling cavity, and ejector system that utilizes a vacuum ejector to direct cooling air from a low-pressure source into the flowpath, enhancing cooling efficiency through a pressure differential and convective cooling mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cooling system is used for the nozzle sleeve, then the structural design is simple, but the cooling efficiency is insufficient under high-pressure combustion conditions
Solution Approach 1:
The nozzle sleeve is divided into multiple functional layers: an outer shell, an intermediate cooling cavity, and an inner liner. This segmentation allows each layer to perform its specific function - the shell provides structural integrity, the cooling cavity enables efficient heat dissipation through channels, and the liner protects against combustion erosion. This segmented structure resolves the contradiction by achieving superior cooling efficiency while maintaining manageable structural complexity through functional specialization.
Solution Approach 2:
The cooling cavity is nested within the nozzle sleeve structure, with cooling channels formed between the shell and liner. The liner is nested within the cooling cavity, and the ejector system is nested at the downstream end. This nested configuration allows the cooling system to be integrated within the existing nozzle structure without requiring additional external components, thereby improving cooling efficiency while avoiding excessive structural complexity.
2Reliability
If high-pressure cooling air is used directly, then cooling effectiveness is high, but the pressure differential required for effective ejector operation cannot be achieved
Solution Approach 1:
The ejector acts as an intermediary device that mediates between the high-pressure combustion products in the flowpath and the low-pressure cooling air source. It uses the high-velocity combustion products to create a vacuum effect that draws cooling air into the cooling cavity and directs it onto the liner. This intermediary mechanism resolves the contradiction by enabling effective cooling transfer without requiring the cooling air source to be at high pressure, thus achieving cooling effectiveness while maintaining the necessary pressure differential.
Solution Approach 2:
The ejector system utilizes pneumatic principles by employing the high-velocity combustion products as a driving fluid to create a vacuum and transport the cooling air. The ejector converts the kinetic energy of the combustion products into pressure differential, which then drives the cooling air flow through the cooling cavity and onto the liner surface. This pneumatic approach resolves the contradiction by achieving effective cooling air delivery without requiring high-pressure cooling air sources.
3Ease of manufacture
If the nozzle sleeve structure is simplified, then manufacturing is easier, but cooling coverage and thermal protection are insufficient
Solution Approach 1:
The cooling cavity is designed with localized cooling channels that are positioned to provide targeted thermal protection to the liner in high-heat zones. The cooling air is directed specifically where it is needed most - along the liner surface exposed to combustion products. This local quality approach resolves the contradiction by providing enhanced thermal protection in critical areas without requiring a uniformly complex structure throughout the entire nozzle sleeve, thus maintaining manufacturing feasibility while improving thermal protection where required.
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 design achieves enhanced cooling efficiency by effectively utilizing low-pressure cooling air to convectively cool the nozzle components, thereby improving the durability and performance of the nozzle under high-pressure combustion conditions.
Implementation Method 1
The ejector is configured to direct cooling air from the cooling cavity into the flowpath. The nozzle sleeve may be configured to receive cooling air in the cooling cavity from the fluid source at a pressure that is less than a pressure of combustion products flowing in the flowpath along the liner.
Implementation Method 2
The design achieves enhanced cooling efficiency by effectively utilizing low-pressure cooling air to convectively cool the nozzle components
Data Source
AI summary
An apparatus is provided for an aircraft engine. This apparatus includes a variable area nozzle. The variable area nozzle includes a nozzle wall, a nozzle sleeve, an actuation system and a flowpath extending axially along an axis through the variable area nozzle and radially between the nozzle wall and the nozzle sleeve. The nozzle sleeve includes a shell, a liner, a cooling cavity and an ejector. The shell extends axially along and circumferentially about the axis. The liner axially overlaps and circumscribes the shell. The cooling cavity is formed by and radially between the shell and the liner. The ejector is arranged at a downstream end of the liner along the flowpath. The ejector fluidly couples the cooling cavity to the flowpath. The actuation system is configured to move the nozzle sleeve axially along the axis relative to the nozzle wall.