Three-Stream Turbofan Layout for Thrust, Weight, and Thermal Balance
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Solution Overview
Problem
Conventional turbofan engine design faces challenges in increasing fan diameter for higher thrust while maintaining propulsive efficiency, leading to installation difficulties, weight issues, and thermal demands, with existing designs failing to optimize packaging, weight, and thermal management.
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 manage airflow and thermal loads, and defining optimal thrust to power and core bypass ratios to enhance propulsive efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If fan diameter is increased for higher thrust, then thrust is improved, but installation difficulty increases
Solution Approach 1:
The engine is divided into three separate airflow streams (core stream, mid-bypass stream, and outer bypass stream), each with dedicated fans and ducts. This segmentation allows independent optimization of each stream's thrust contribution, enabling high total thrust without requiring a single oversized fan that would create installation difficulties.
Solution Approach 2:
The patent introduces a radial dimension to the bypass airflow by creating multiple annular bypass passages at different radii (mid-bypass and outer bypass). This multi-dimensional airflow architecture allows thrust to be generated across different radial zones, effectively distributing the thrust-generation function and avoiding the need for a single large-diameter fan.
2Force
If fan diameter is increased for higher thrust, then thrust is improved, but weight increases
Solution Approach 1:
The propulsion function is segmented across three streams with separate fans (inner fan, mid-fan, outer fan). Each fan operates at optimized dimensions and speeds, avoiding the weight penalty of a single large fan. The segmented architecture allows lighter individual components that collectively generate higher thrust.
Solution Approach 2:
Each fan stream can operate independently at its optimal rotational speed and load conditions. The variable geometry components allow dynamic adjustment of airflow distribution among streams, enabling the engine to maintain high efficiency across varying thrust requirements without the weight overhead of oversized components designed for maximum thrust.
3Force
If fan diameter is increased for higher thrust, then thrust is improved, but thermal demand increases
Solution Approach 1:
The thermal load is segmented across three separate airflow streams, with each stream handling a portion of the total thermal energy. The core stream handles high-temperature combustion gases, while the two bypass streams handle cooler airflow. This segmentation distributes thermal management requirements, avoiding concentration of thermal demand in a single large fan system.
Solution Approach 2:
The bypass streams act as thermal intermediaries, providing cooler airflow that can be used for cooling engine components and reducing overall thermal demand. The multi-stream architecture introduces thermal buffering capacity, where the bypass airflow mediates between the hot core exhaust and the external environment, reducing peak thermal loads.
4Device complexity
If conventional two-stream design is used, then design simplicity is maintained, but propulsive efficiency is suboptimal
Solution Approach 1:
The bypass airflow is segmented into two separate streams (mid-bypass and outer bypass), each with dedicated fans and ducts. This segmentation allows independent optimization of each bypass stream's propulsive efficiency, with the mid-bypass stream handling higher-pressure airflow and the outer bypass stream handling lower-pressure airflow, maximizing overall propulsive efficiency.
Solution Approach 2:
Each stream is designed with local optimizations tailored to its specific operating conditions. The inner fan and mid-bypass stream are optimized for higher-pressure, lower-volume airflow, while the outer fan and outer bypass stream are optimized for lower-pressure, higher-volume airflow. This local quality approach maximizes propulsive efficiency at each stage of the airflow expansion process.
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, addresses packaging and weight concerns, and enhances thermal management, facilitating rapid design selection and avoiding late-stage redesigns.
Implementation Method 1
utilizing variable geometry components and heat exchangers to manage airflow and thermal loads
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, a core cowl, and a booster located downstream of the secondary fan and including a booster rotor blade and a booster cowl, the booster cowl located outward of the booster rotor blade and within the fan duct at the fan duct inlet, 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 booster including a midspan shroud coupled to the booster rotor blade.