Variable Core Cowl Vent Nozzle Area Control
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Solution Overview
Problem
In gas turbine engines, the core cowl vent nozzle area is often larger than needed during 'better-case' conditions, leading to reduced thrust and increased drag, as it is designed for 'worse-case' conditions, resulting in inefficient cooling and propulsion.
Innovation Solution
A variable core cowl vent nozzle system where at least one of the core cowl and primary nozzle is movable to adjust the vent area, using active or passive controls, such as actuators, temperature-sensitive materials, or thermal control systems, to optimize the nozzle area based on flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the core cowl vent nozzle is designed with a large area for worse-case conditions, then cooling capability is improved, but thrust generation deteriorates during better-case conditions
Solution Approach 1:
The core cowl vent nozzle is designed with movable components (flaps, doors, or the entire cowl) that can dynamically adjust the vent area based on operating conditions. This transforms the static nozzle into a dynamic system that optimizes both cooling capability and thrust generation by varying the open area according to whether the engine is in takeoff, cruise, or idle conditions
Solution Approach 2:
The vent area parameter is made variable through mechanical actuation systems. By changing the geometric parameter of the vent area from fixed to variable, the system can optimize performance across different operating regimes - maintaining large area for cooling during takeoff and reducing area for thrust during cruise
2Quantity of substance
If the core cowl vent nozzle area is increased for maximum cooling, then cooling air flow is improved, but drag increases and thrust decreases
Solution Approach 1:
The vent area is made dynamically adjustable with actuators that control flaps or doors. During cruise conditions, the system reduces the open area to minimize drag, while during high-temperature conditions, it increases the area to maximize cooling air flow, thus dynamically optimizing the trade-off between cooling and drag
Solution Approach 2:
Different sections of the cowl can be independently controlled with separate actuators, allowing localized adjustment of vent area. This enables precise control over where cooling air is extracted and how much drag is incurred, optimizing the local flow characteristics for different operating conditions
3Ease of manufacture
If a single static cowl component is used, then manufacturing simplicity is improved, but adaptability to different flight conditions deteriorates
Solution Approach 1:
The cowl is divided into multiple segments or sections, each capable of independent movement controlled by separate actuators. This segmentation allows the system to achieve complex area adjustments while maintaining relatively simple individual components, balancing manufacturing ease with operational adaptability
Solution Approach 2:
The variable area mechanism serves multiple functions: it provides cooling during takeoff, minimizes drag during cruise, and can be controlled through various means (electrical actuators, pneumatic systems, or thermal expansion materials). This multi-functionality justifies the added complexity by delivering adaptability across all flight conditions
Data Source
AI summary
A variable core cowl vent nozzle system is described herein, the system including a core casing at least partially surrounding a core engine of a gas turbine engine, and a core cowl extending aftward from the core casing. The core cowl defines a core cowl vent area between the core cowl and a primary nozzle. At least one of the core cowl and the primary nozzle is movable to vary the core cowl vent area. A method for varying the core cowl vent area by moving one or more of the core cowl and the primary nozzle is also described herein.