Three-Stream Gas Turbine Engine for Fan Packaging Constraints
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Solution Overview
Problem
Conventional gas turbine engine design faces challenges in increasing fan diameter to enhance propulsive efficiency, leading to installation difficulties, weight issues, and thermal demands, while maintaining desired propulsive efficiency and thermal management.
Innovation Solution
A three-stream gas turbine engine design incorporating a primary and secondary fan with a third stream, utilizing a ducted fan to generate airflow through a separate stream, and employing variable geometry components to optimize thrust generation across various operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fan diameter is increased to enhance propulsive efficiency, then propulsive efficiency is improved, but installation difficulty increases, weight increases, and thermal management becomes more challenging
Solution Approach 1:
The engine flow is segmented into three separate streams: a core stream through the turbomachine, a first bypass stream around the core, and a second bypass stream around both the core and first bypass stream. This segmentation allows each stream to be optimized independently, enabling high propulsive efficiency without requiring an excessively large fan diameter, thus avoiding installation and packaging difficulties.
Solution Approach 2:
The patent introduces a radial dimension to the bypass flow by implementing a second bypass stream that flows radially outward around both the core and first bypass stream. This multi-dimensional flow arrangement allows the engine to achieve high propulsive efficiency through complex three-dimensional flow management rather than simply increasing fan diameter in one dimension.
2Loss of energy
If fan diameter is increased to enhance propulsive efficiency, then propulsive efficiency is improved, but weight increases
Solution Approach 1:
By segmenting the airflow into three separate streams, the patent achieves high propulsive efficiency through optimized mass flow distribution rather than relying on a single large fan. This allows the use of smaller, lighter fan components while maintaining or improving overall propulsive efficiency, thus avoiding the weight penalty associated with larger single-stream fans.
Solution Approach 2:
Each bypass stream is given distinct characteristics and optimization: the first bypass stream is optimized for certain operating conditions while the second bypass stream is optimized for other conditions. This local optimization of different flow paths allows the engine to maintain high propulsive efficiency across various flight regimes without requiring excessive weight in any single component.
3Loss of energy
If fan diameter is increased to enhance propulsive efficiency, then propulsive efficiency is improved, but thermal management becomes more challenging
Solution Approach 1:
The three-stream configuration segments the hot core exhaust from the cooler bypass flows, with the second bypass stream providing additional cooling capability by flowing around both the core and first bypass stream. This segmentation allows independent thermal management of each stream, enabling high propulsive efficiency while maintaining controllable thermal conditions through the cooler bypass air mixing with the hot core stream.
4Power
If variable geometry components are added to optimize thrust generation, then thrust optimization is improved, but device complexity increases
Solution Approach 1:
The patent incorporates variable geometry components including adjustable fan blade pitch, variable area nozzles for each stream, and adjustable guide vanes that can change configuration based on operating conditions. These dynamic elements allow the engine to optimize thrust generation across different flight regimes (takeoff, climb, cruise, descent) by adjusting the flow characteristics of each bypass stream and the core stream independently, achieving superior thrust optimization despite the increased complexity.
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
Maintains or improves overall propulsive efficiency, reduces packaging and weight concerns, and enhances thermal management capabilities, facilitating rapid design selection and avoiding late-stage redesigns.
Implementation Method 1
The compressors compress air which is channeled to the combustor
Implementation Method 2
The combustion gases are channeled to the turbine(s) which extracts energy from the combustion gases
Data Source
AI summary
A gas turbine engine includes a turbomachine defining an engine inlet to an inlet duct, a fan duct inlet to a fan duct, and a core inlet to a core duct, a primary fan driven by the turbomachine, a secondary fan located downstream of the primary fan within the inlet duct, and a booster located downstream of the secondary fan and comprising a booster rotor blade, an inlet guide vane, and booster cowl, the booster cowl separating an upstream portion of the fan duct into an upper fan duct having an upper fan duct inlet and a lower fan duct having a lower fan duct inlet, the upper fan duct inlet and lower fan duct inlet collectively forming the fan duct inlet, the inlet guide vane located forward of the booster rotor blade.