Three-Stream Gas Turbine Architecture for Thrust Without Larger Fans
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Solution Overview
Problem
Conventional turbofan engine design faces challenges in increasing fan diameter for higher thrust while maintaining propulsive efficiency, as it leads to weight and thermal issues, and the need for larger nacelles that are weight-prohibitive and thermally demanding.
Innovation Solution
A three-stream gas turbine engine design incorporating a primary and secondary fan, with a ducted secondary fan providing airflow to a third stream, allowing for optimized thrust to power airflow and core bypass ratios, which balances 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 weight and thermal issues worsen
Solution Approach 1:
The engine flow is segmented into three separate streams: a core stream through the turbomachine, a fan stream from the primary fan, and a third stream from the secondary fan. This segmentation allows each stream to be optimized independently, enabling thrust to be increased through the third stream without proportionally increasing the primary fan size and associated weight
Solution Approach 2:
The patent introduces a third stream dimension to the conventional two-stream turbofan architecture. By adding the secondary fan-driven third stream, the engine achieves additional thrust capability without increasing the primary fan diameter, effectively adding a dimensional degree of freedom to the thrust generation system
2Force
If fan diameter is increased for higher thrust, then thrust is improved, but thermal management becomes more difficult
Solution Approach 1:
The thermal management system is segmented into separate pathways for each stream. The third stream from the secondary fan provides dedicated airflow for thermal management of specific engine components, allowing independent optimization of cooling requirements without being constrained by primary fan size
Solution Approach 2:
The third stream acts as an intermediary cooling flow that can be directed to specific thermal management needs. This separate airflow pathway provides flexible thermal control without requiring the primary fan to be oversized for thermal management purposes
3Weight of moving object
If primary fan size is reduced, then weight is reduced, but propulsive efficiency may deteriorate
Solution Approach 1:
Propulsive efficiency is maintained by segmenting the thrust generation across three optimized streams. The primary fan is reduced in size while the secondary fan and third stream compensate for the reduced bypass ratio, allowing weight reduction without sacrificing overall propulsive efficiency
Solution Approach 2:
The patent optimizes the airflow distribution parameters among the three streams to maintain propulsive efficiency. By adjusting the core bypass ratio and thrust to power airflow ratio within specific ranges, the system achieves efficient operation with a smaller primary fan
4Loss of energy
If three-stream design is implemented, then propulsive efficiency is improved, but device complexity increases
Solution Approach 1:
The secondary fan is merged with the existing engine architecture, utilizing the same drive shaft and integration points as the primary fan. This merging approach allows the third stream to be added with minimal additional complexity, as both fans share common mounting and drive mechanisms
Data Source
AI summary
A gas turbine engine includes a turbomachine including a compressor section, a combustion section, and a turbine section arranged in serial flow order, the turbomachine defining a fan duct inlet to a fan duct, and a core inlet to a core duct, a fan driven by the turbomachine, and a booster downstream of the fan, the booster comprising a booster rotor blade and a booster cowl.