Third-Stream Turbofan Layout for Thrust and Thermal Balance
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Solution Overview
Problem
Conventional turbofan engine design faces challenges in increasing fan diameter for higher thrust, leading to installation difficulties, weight issues, and thermal demands, while maintaining propulsive efficiency.
Innovation Solution
A gas turbine engine with a primary and secondary fan configuration, incorporating a third stream with variable geometry components and heat exchangers, optimizing thrust to power airflow and core bypass ratios to balance propulsive efficiency, packaging, and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If fan diameter is increased for higher thrust, then thrust is improved, but installation difficulty increases, weight increases, and thermal demands increase
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 thrust generation without requiring a single large fan diameter, thus reducing installation difficulty while maintaining thrust output.
Solution Approach 2:
The patent introduces a third stream (second bypass stream) that flows through an annular passage between the core cowl and the first bypass duct. This adds a dimensional aspect to the airflow configuration, allowing thrust to be generated through multiple parallel pathways rather than relying on a single large-diameter fan, thereby reducing installation complexity.
2Force
If fan diameter is increased for higher thrust, then thrust is improved, but weight increases
Solution Approach 1:
By dividing the thrust generation into three separate airflow streams, each stream can use smaller, lighter components. The primary fan, split into multiple bypass streams and a core stream, reduces the diameter and weight of individual fan blades and supporting structures while collectively generating the required thrust.
Solution Approach 2:
The addition of a second bypass stream through an annular passage utilizes unused spatial volume in the engine configuration. This allows thrust to be generated through an additional pathway without requiring larger outer dimensions, thereby increasing thrust capability without proportionally increasing engine weight.
3Force
If fan diameter is increased for higher thrust, then thrust is improved, but thermal demands increase
Solution Approach 1:
The thermal load is distributed across three separate airflow streams. The core stream handles high-temperature combustion gases, while the two bypass streams handle cooler air. This segmentation allows for targeted thermal management in each stream, reducing the overall thermal demands on the engine system compared to a single large fan configuration.
Solution Approach 2:
The patent introduces a heat exchanger that utilizes the cooler second bypass stream to absorb heat from the core stream. This intermediary heat transfer mechanism reduces thermal demands on the engine by pre-cooling the core exhaust gases using the thermal energy in the second bypass airflow, thereby managing thermal loads more efficiently.
4Productivity
If third stream is added with variable geometry components and heat exchangers, then propulsive efficiency is improved, but device complexity increases
Solution Approach 1:
The patent incorporates variable geometry components including adjustable inlet guide vanes and variable area nozzles in the third stream. These dynamic elements allow the engine to optimize airflow distribution and thrust generation across different operating conditions, improving propulsive efficiency by adapting to varying flight regimes despite the increased device complexity.
Solution Approach 2:
The variable geometry components enable changes in airflow parameters such as velocity, pressure, and temperature distribution across the three streams. By dynamically adjusting these parameters through movable vanes and adjustable nozzles, the engine optimizes propulsive efficiency for different operating conditions, balancing the trade-off between improved performance and increased structural 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 propulsive efficiency by reducing primary fan size, addressing weight and thermal concerns, and facilitating rapid design selection through defined airflow ratio relationships.
Implementation Method 1
incorporating a third stream with variable geometry components and heat exchangers
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.