Turbofan Cowl Assembly Thrust Reverser Efficiency
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Solution Overview
Problem
Existing turbofan engines experience undesirable increases in fuel burn when operating the thrust reverser assembly, as the airflow discharged through it reduces engine efficiency during peak operation.
Innovation Solution
A method and assembly that involves a repositionable second cowl within the thrust reverser assembly, coupled with flow directing members, to vary the fan nozzle duct area and control airflow, thereby improving engine efficiency by selectively positioning the cowl between different operational positions to manage airflow through the fan nozzle duct and thrust reverser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the thrust reverser assembly is operated to discharge airflow, then reverse thrust capability is provided, but fuel burn increases and engine efficiency decreases
Solution Approach 1:
The second cowl is made axially translatable relative to the first cowl, allowing dynamic adjustment of the fan nozzle duct area. During reverse thrust operations, the second cowl can be repositioned to optimize the duct area, enabling the system to adapt to different operating conditions and reduce fuel burn while maintaining reverse thrust capability.
Solution Approach 2:
The invention changes the parameter of fan nozzle duct area by translating the second cowl axially. This parameter change allows optimization of airflow characteristics during reverse thrust operations, improving engine efficiency by reducing the area through which air is discharged when reverse thrust is not needed.
2Loss of energy
If the fan nozzle duct area is reduced to improve engine efficiency, then fuel burn decreases, but airflow capability for thrust reverser operations is limited
Solution Approach 1:
The axially translatable second cowl enables dynamic adjustment of the fan nozzle duct area based on operational requirements. During cruise or idle conditions, the duct area can be reduced to improve engine efficiency and reduce fuel burn. When reverse thrust is required, the second cowl can be repositioned to increase the duct area and restore full airflow capability.
Solution Approach 2:
The thrust reverser assembly with the movable second cowl serves multiple functions: it optimizes engine efficiency during normal operation by controlling fan nozzle duct area, and provides reverse thrust capability when needed by repositioning the second cowl to allow airflow through the thrust reverser. This multi-functionality resolves the contradiction between efficiency and productivity.
Data Source
AI summary
A method for operating a turbofan engine assembly is provided. The turbofan engine assembly includes a core cowl which circumscribes the core gas turbine engine, a nacelle positioned radially outward from the core cowl, a fan nozzle duct having an area defined between the core cowl and a portion of the nacelle, a first cowl and a second cowl that define a portion of the nacelle wherein the second cowl is repositionable with respect to the first cowl, and a thrust reverser assembly wherein the second cowl surrounds the thrust reverser assembly. The method includes varying an operating speed of the fan assembly from a first operating speed to a second operating speed. The method further includes selectively positioning the second cowl between a first operational position and a second operational position to vary the area of the fan nozzle duct to facilitate improving engine efficiency at the second operating speed. The method further includes selectively positioning the second cowl between the second operational position and a third operational position to vary an amount of air flowing through the fan nozzle duct and the thrust reverser assembly, wherein the second operational position substantially prevents airflow from flowing through the thrust reverser assembly to improve the efficiency of the turbofan engine, and wherein the third operational position directs airflow through the thrust reverser assembly.