Translating Core Cowl for Turbofan Engine Flow Control
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Solution Overview
Problem
High bypass turbofan engines face challenges with increased weight, noise, and drag due to large nacelle size, which negatively impact performance during diverse flight conditions beyond normal cruise operations.
Innovation Solution
A gas turbine engine system with a core cowl featuring a translating section that adjusts the discharge airflow cross-sectional area in response to operability conditions, using a sensor and controller to move the section between positions, thereby optimizing airflow for varying flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsive efficiency is improved, but nacelle size increases resulting in increased weight, noise and drag
Solution Approach 1:
The core cowl includes a translating section that can move axially relative to the stationary section, dynamically adjusting the discharge airflow cross-sectional area. This dynamic adjustment allows the engine to optimize performance across different flight conditions without requiring a permanently oversized nacelle, thereby reducing weight while maintaining propulsive efficiency.
Solution Approach 2:
The translating section changes the geometric parameter of the discharge airflow cross-sectional area in response to detected operability conditions. By varying this parameter, the engine adapts to different flight conditions (takeoff, climb, cruise, descent, landing) to maintain optimal propulsive efficiency without the penalty of a constantly large nacelle size.
2Productivity
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsive efficiency is improved, but noise increases
Solution Approach 1:
The translating section dynamically adjusts the discharge airflow cross-sectional area based on detected operability conditions. During conditions where noise is a concern (such as approach and landing), the translating section can reposition to optimize airflow and reduce noise generation, while maintaining propulsive efficiency during other phases of flight.
3Productivity
If a large diameter fan is used to achieve adequate turbofan engine efficiency, then propulsive efficiency is improved, but drag increases
Solution Approach 1:
The translating section provides dynamic adjustment of the discharge airflow cross-sectional area, allowing the engine to optimize its aerodynamic characteristics for different flight conditions. This reduces drag by preventing airflow separation and optimizing the exhaust jet interaction with the bypass flow, thereby maintaining propulsive efficiency without the constant drag penalty of a large fixed nacelle.
4Adaptability or versatility
If the core cowl translating section is added to vary discharge airflow cross-sectional area, then engine performance during diverse flight conditions is improved, but device complexity increases
Solution Approach 1:
The core cowl is segmented into a stationary section and a translating section that can move independently. This segmentation allows the translating section to perform the adaptive function of varying discharge airflow area, while the stationary section maintains the basic structural integrity. The segmentation enables improved adaptability with relatively simple structural modifications.
5Force
If the translating section moves to increase discharge airflow cross-sectional area, then thrust is improved during takeoff, but the mechanism complexity increases
Solution Approach 1:
The core cowl is divided into stationary and translating sections, with the translating section specifically designed to move for thrust optimization. This segmentation isolates the complexity of the moving mechanism to only the portion needed for thrust enhancement, rather than making the entire core cowl complex.
Solution Approach 2:
The controller receives input from sensors detecting operability conditions and automatically positions the translating section to optimize thrust. This feedback control system simplifies the overall complexity by using automated control rather than requiring complex mechanical linkages for manual adjustment.
Data Source
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AI summary
An example core nacelle includes a core cowl positioned adjacent to an inner duct boundary of a fan bypass passage having an associated discharge airflow cross-sectional area. The core cowl includes a translating section located aft of an exit guide vane positioned within the fan bypass passage. The translating section is moveable to vary the discharge airflow cross-sectional area.