Three-Stream Gas Turbine Engine for Fan Diameter Tradeoffs
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Solution Overview
Problem
Conventional gas turbine engine design faces challenges in increasing fan diameter for improved propulsive efficiency while managing weight, thermal demands, 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 variable geometry components and heat exchangers to optimize thrust to power airflow and core bypass ratios, maintaining or enhancing propulsive efficiency while addressing weight and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fan diameter is increased for improved propulsive efficiency, then propulsive efficiency is improved, but weight increases and packaging becomes more difficult
Solution Approach 1:
The engine airflow is divided into three separate streams: a core stream through the combustor, a first bypass stream, and a second bypass stream. This segmentation allows each stream to be optimized independently, enabling improved propulsive efficiency without requiring a single oversized fan that would increase weight and packaging difficulty.
Solution Approach 2:
The patent introduces a third dimension to the traditional two-stream architecture by adding a second bypass stream with its own dedicated fan. This dimensional expansion of the airflow architecture enables greater flexibility in optimizing propulsive efficiency while maintaining manageable weight and packaging characteristics through distributed fan arrangements.
2Loss of energy
If fan diameter is increased for improved propulsive efficiency, then propulsive efficiency is improved, but installation becomes more difficult
Solution Approach 1:
By segmenting the bypass airflow into two separate streams with different fan arrangements, the engine can be installed in configurations that better fit aircraft constraints. The first and second bypass streams can be routed through different pathways, providing installation flexibility that a single large fan cannot achieve.
Solution Approach 2:
The variable geometry components enable the engine to adapt its performance characteristics to different installation environments and operating conditions, making the engine easier to install and integrate into various aircraft platforms while maintaining high propulsive efficiency across different configurations.
3Loss of energy
If variable geometry components and heat exchangers are added to optimize thrust to power airflow ratio, then propulsive efficiency is improved, but device complexity increases
Solution Approach 1:
The heat exchangers and variable geometry components serve multiple functions: they optimize the thrust to power airflow ratio, manage thermal loads across the three streams, and enable the engine to adapt to different operating conditions. This multi-functionality justifies the added complexity by delivering significant improvements in propulsive efficiency and operational flexibility.
Solution Approach 2:
The variable geometry components allow dynamic adjustment of airflow parameters (pressure ratios, mass flow distribution) across the three streams to optimize propulsive efficiency under different operating conditions. The heat exchangers enable thermal parameter optimization, allowing the engine to maintain high efficiency across a wide range of flight regimes despite the increased device complexity.
Data Source
AI summary
A gas turbine engine is provided. The 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; and a secondary fan located downstream of the primary fan within the inlet duct. The gas turbine engine defines a thrust to power airflow ratio between 3.5 and 100 and a core bypass ratio between 0.1 and 10, wherein the thrust to power airflow ratio is a ratio of an airflow through a bypass passage over the turbomachine plus an airflow through the fan duct to an airflow through the core duct, and wherein the core bypass ratio is a ratio of the airflow through the fan duct to the airflow through the core duct.