Three-Stream Airflow Mixer Assembly for Fan Diameter Packaging
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Solution Overview
Problem
Conventional gas turbine engine design faces challenges in increasing fan diameter for improved propulsive efficiency while managing thermal demands, weight, and packaging constraints, leading to potential decreases in overall efficiency and installation difficulties.
Innovation Solution
A three-stream gas turbine engine design incorporating a primary and secondary fan, with a third stream airflow, utilizing specific airflow ratio relationships to maintain or enhance propulsive efficiency, address thermal management, and reduce weight and packaging issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fan diameter is increased for improved propulsive efficiency, then propulsive efficiency is improved, but thermal demands, weight, and packaging constraints increase leading to installation difficulties
Solution Approach 1:
The engine is divided into three separate airflow streams: a core stream through the combustor, a bypass stream around the core, and a fan stream. This segmentation allows independent optimization of each stream's thermal and aerodynamic characteristics, enabling the fan diameter to be increased for propulsive efficiency without proportionally increasing thermal management complexity in any single stream.
Solution Approach 2:
The airflow mixer assembly serves multiple functions simultaneously: it mixes the three different temperature and pressure streams, provides thermal management by controlling heat distribution, and contributes to propulsive efficiency through optimized exhaust flow. This multi-functionality addresses the contradiction by consolidating several subsystems into one integrated assembly.
2Productivity
If fan diameter is increased for improved propulsive efficiency, then propulsive efficiency is improved, but weight increases
Solution Approach 1:
The mixer assembly combines the core, bypass, and fan streams into a unified exhaust flow path. By merging these streams and their associated control systems into a single integrated assembly, the overall engine weight is reduced compared to having separate systems for each stream, offsetting the weight increase from the larger fan diameter.
3Productivity
If fan diameter is increased for improved propulsive efficiency, then propulsive efficiency is improved, but packaging constraints increase leading to installation difficulties
Solution Approach 1:
The bypass stream is arranged to flow around the core stream, and the mixer assembly is positioned to receive and combine these streams in a nested configuration. This nesting allows the three-stream architecture to fit within a compact volume, enabling a larger fan diameter for propulsive efficiency without proportionally increasing the overall engine packaging volume.
4Productivity
If three-stream design is implemented to maintain propulsive efficiency, then propulsive efficiency is maintained or enhanced, but device complexity increases
Solution Approach 1:
The airflow mixer assembly acts as an intermediary component that receives three separate streams with different thermal and aerodynamic properties and combines them into a single unified exhaust flow. This intermediary function simplifies the overall system architecture by providing a centralized mixing and control point, reducing the complexity that would otherwise arise from managing three independent streams throughout the engine.
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 design maintains or improves propulsive efficiency while addressing weight and thermal management concerns, facilitating rapid down-selection of suitable engine configurations and avoiding late-stage redesigns.
Implementation Method 1
The mixer is configured for mixing a low pressure airflow from the low pressure duct with an exhaust gas flow from the exhaust
Data Source
AI summary
A gas turbine engine is provided having a turbomachine; a primary fan driven by the turbomachine; a secondary fan located downstream of the primary fan within the inlet duct, the gas turbine engine defining a thrust to power airflow ratio between 3.5 and 100 and a core bypass ratio between 0.1 and 10; and an airflow mixer assembly comprising: a low pressure duct positioned within the core cowl; a plenum extending along the circumferential direction located downstream of the low pressure duct and in fluid communication with the low pressure duct; an inner shroud located downstream of the plenum and downstream of the exhaust and in fluid communication with both the plenum and the exhaust; and an outer shroud located outward of the plenum along the radial direction and extending along the circumferential direction and along the axial direction over and downstream of the inner shroud.