Slim-line Nacelle with Variable Area Fan Nozzle
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Solution Overview
Problem
High bypass turbofan engines face challenges due to the large size of their nacelles, which increase weight and drag, offsetting the efficiency gains from propulsion thrust, particularly during windmilling conditions where airflow separation can occur.
Innovation Solution
A gas turbine engine with a nacelle assembly featuring a variable area fan nozzle and boundary layer control devices that adjust airflow based on operability conditions, such as windmilling, to increase discharge airflow area and prevent airflow separation, thereby reducing nacelle size and drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large diameter fan is used to achieve adequate turbofan engine efficiency in high bypass turbofans, then propulsion thrust is improved, but the nacelle size increases resulting in increased weight and drag
Solution Approach 1:
The patent applies a variable area fan nozzle that can dynamically change its discharge airflow area between a first position (smaller area) and a second position (larger area). This dynamic adjustment allows the nacelle to adapt to different operating conditions, enabling a smaller overall nacelle size while maintaining the capability to deliver high propulsion thrust when needed.
Solution Approach 2:
The invention changes the physical parameter of the fan nozzle discharge area by moving it between different positions. This parameter change allows the system to achieve different airflow characteristics without requiring a permanently large nacelle structure, thus reducing weight while maintaining performance capability.
2Power
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsion thrust is improved, but drag increases offsetting the efficiency gains
Solution Approach 1:
The variable area fan nozzle dynamically adjusts the discharge airflow area to optimize performance across different flight conditions. During conditions requiring high thrust, the nozzle opens to a larger area; during other conditions, it closes to a smaller area, reducing the effective size and thus reducing drag.
Solution Approach 2:
By changing the discharge airflow area parameter of the fan nozzle, the system optimizes the balance between thrust generation and drag reduction, allowing high propulsion efficiency without the continuous penalty of a large nacelle size.
3Weight of stationary object
If the nacelle size is reduced to decrease weight and drag, then efficiency is improved, but airflow separation may occur during windmilling conditions
Solution Approach 1:
The variable area fan nozzle works in conjunction with boundary layer control devices that can be actuated during specific operability conditions such as windmilling. This dynamic control system prevents airflow separation by introducing boundary layer control airflow when needed, allowing a smaller nacelle design without sacrificing reliability.
Solution Approach 2:
The boundary layer control device acts as an intermediary mechanism that introduces controlled airflow to prevent separation between the main airflow and the nacelle surface during critical conditions like windmilling, enabling a smaller nacelle design to maintain reliable flow attachment.
4Reliability
If boundary layer control devices are actuated to prevent airflow separation, then reliability is improved, but device complexity increases
Solution Approach 1:
The boundary layer control device is integrated with the existing variable area fan nozzle system and controlled by the same controller that manages nozzle position. This multi-functional approach allows the control system to handle both nozzle positioning and boundary layer control without requiring completely separate control mechanisms, thus limiting the increase in 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
The solution allows for a slim-line nacelle design with reduced weight and drag, maintaining separation-free airflow and improving engine efficiency by dynamically adjusting the fan nozzle and boundary layer control during various flight conditions.
Implementation Method 1
at least one boundary layer control device positioned near one of the inlet lip section and the inlet internal diffuser section. A controller is configured to move the variable area fan nozzle from the first position to the second position and to actuate the at least one boundary layer control device to introduce an airflow in response to an operability condition
Implementation Method 2
maintaining separation-free airflow and improving engine efficiency by dynamically adjusting the fan nozzle and boundary layer control during various flight conditions
Data Source
AI summary
A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a nacelle assembly that includes an inlet lip section and an inlet internal diffuser section downstream of the inlet lip section. A variable area fan nozzle is positioned near an aft segment of the nacelle assembly, the variable area fan nozzle adaptable to move between a first position having a first discharge airflow area and a second position having a second discharge airflow area greater than the first discharge airflow area. At least one boundary layer control device is positioned near one of the inlet lip section and the inlet internal diffuser section. A controller is configured to move the variable area fan nozzle from the first position to the second position and to actuate the at least one boundary layer control device to introduce an airflow in response to an operability condition.