Variable Area Exhaust Mixer for Gas Turbine Bypass Ratio Control
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Solution Overview
Problem
Variable cycle gas turbine engines face challenges in efficiently managing the bypass ratio and thrust augmentation across a range of operating conditions, requiring adaptable exhaust nozzle designs that can vary significantly to optimize performance and efficiency.
Innovation Solution
A variable area exhaust mixer with multiple doors and trailing edge flaps that control passage entrances and exhausts, allowing for selective adjustment of the bypass ratio between fan and core flow paths, integrated with spraybars for thrust augmentation, enabling efficient mixing and propulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the exhaust nozzle size is varied considerably to accommodate large changes in the cycle, then the bypass ratio can be adjusted to optimize performance across different operating conditions, but the device complexity increases due to the need for multiple moving parts including doors and flaps
Solution Approach 1:
The exhaust mixer is divided into multiple circumferentially arrayed vanes with individual doors and trailing edge flaps. Each vane assembly can be independently controlled to adjust the bypass ratio, allowing precise adaptation to different operating conditions while maintaining manageable complexity through modular design
Solution Approach 2:
The exhaust mixer incorporates movable doors and trailing edge flaps that can dynamically adjust the passage area to control the bypass ratio. This dynamic adjustment capability allows the system to adapt to varying flight conditions, optimizing performance across different operating regimes
2Ease of operation
If multiple doors and trailing edge flaps are used to control passage flow, then the bypass ratio can be precisely controlled, but the manufacturing complexity and cost increase
Solution Approach 1:
The exhaust mixer is segmented into multiple identical vane assemblies, each with its own door and trailing edge flap. This modular approach allows for standardized manufacturing of individual units that can be assembled circumferentially, simplifying production while maintaining precise flow control capability
Solution Approach 2:
The design allows for adjustment of geometric parameters such as door angle and flap position to control the bypass ratio. By varying these parameters, the system can achieve precise flow control without requiring complex mechanical mechanisms, thereby simplifying manufacturing
3Productivity
If the exhaust mixer is designed with multiple circumferentially arrayed vanes, then the mixing efficiency is improved, but the weight of the moving parts increases
Solution Approach 1:
The exhaust mixer uses multiple circumferentially arrayed vanes to create multiple mixing streams simultaneously. This segmentation approach increases mixing efficiency by distributing the mixing action across multiple locations, while each individual vane maintains a manageable weight
Solution Approach 2:
The exhaust mixer combines multiple flow streams through the circumferentially arrayed vanes to achieve enhanced mixing efficiency. By merging the control functions of multiple vanes into a single integrated structure, the design achieves improved mixing while minimizing the total weight of moving parts
Data Source
AI summary
A variable area exhaust mixer is provided for a gas turbine engine. The variable area exhaust mixer includes an outer wall with a multiple of doors. Each of the multiple of doors is operable to control a passage entrance into at least one of a multiple of circumferentially arrayed vanes with a respective strut flow passage which essentially alters its bypass ratio during flight to match requirements.