Axial Flow Control for Turbofan Bypass Efficiency

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Solution Overview

Problem

Current gas turbine engines face challenges in balancing fuel efficiency and thrust requirements, as high bypass engines prioritize fuel efficiency over thrust, while low bypass engines generate more thrust but at the cost of reduced fuel efficiency.

Innovation Solution

A gas turbine engine design featuring a core engine, first and second bypass passages, and a flow control mechanism within the second bypass passage that translates axially between open and closed positions to control bypass airflow, optimizing thrust and fuel efficiency by varying the outlet area without imparting a radial component to airflow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a high bypass passage is used, then fuel efficiency is improved, but thrust production is reduced

Engineering Contradiction:

Improvefuel efficiencyVSAvoidthrust production

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The patent applies a movable flow control device in the second bypass passage that can translate axially between open and closed positions. This dynamic adjustment allows the engine to vary the bypass airflow area in real-time, transitioning between high bypass mode for fuel efficiency and low bypass mode for thrust production, thereby resolving the contradiction between fixed design trade-offs

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flow control device changes the effective area parameter of the second bypass passage by moving axially. When the device is in the closed position, the bypass area is reduced, directing more flow through the core engine for thrust. When open, the bypass area increases, improving fuel efficiency. This parameter change enables the engine to adapt to different operational requirements

Inventive Principle:

Principle #35Parameter changes

2Power

If a low bypass passage is used, then thrust production is improved, but fuel efficiency is reduced

Engineering Contradiction:

Improvethrust productionVSAvoidfuel efficiency

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The movable flow control device enables dynamic reconfiguration of the bypass passage area. During high thrust requirements, the device closes to reduce bypass area and direct flow through the core engine. During fuel-efficient operation, the device opens to increase bypass area. This dynamic capability allows a single engine design to achieve both high thrust and fuel efficiency as needed

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The bypass system is segmented into a first bypass passage and a second bypass passage with independent flow control. This segmentation allows selective control of bypass airflow through the second passage while maintaining the first passage open, enabling fine-tuned adjustment of total bypass flow to optimize the thrust-efficiency trade-off

Inventive Principle:

Principle #1Segmentation

3Use of energy by moving object

If bypass airflow is increased, then fuel efficiency is improved, but thrust production is reduced

Engineering Contradiction:

Improvefuel efficiencyVSAvoidthrust production

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The flow control device is actuated by a feedback mechanism that responds to engine operating conditions. Sensors monitor parameters such as thrust requirements and fuel consumption, providing feedback to the actuator to adjust the flow control device position accordingly, automatically optimizing the balance between bypass airflow and thrust production

Inventive Principle:

Principle #23Feedback

4Productivity

If a variable cycle engine is used, then operational efficiency is improved, but engine complexity is increased

Engineering Contradiction:

Improveoperational efficiencyVSAvoidengine complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The flow control device serves multiple functions: it controls bypass airflow, adjusts thrust production, optimizes fuel efficiency, and adapts to different operating modes (takeoff, cruise, combat). This multi-functionality is achieved through a single axial translation mechanism, reducing the need for separate systems for each function and thereby limiting the increase in overall engine complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution enhances engine performance by allowing for adjustable bypass airflow, improving both thermal and propulsive efficiencies while enabling increased thrust production with reduced fuel consumption.

Implementation Method 1

The flow control translates axially between an open position and a closed position

Methodology Applied

Scientific EffectAxial translation of flow control:

Implementation Method 2

the flow control includes a tear-drop shape in cross-section that imparts substantially no radial component to airflow exiting the outlet of the second bypass passage

Methodology Applied

Scientific EffectFlow control geometry:

Data Source

PatentUS9506423B2Flow control device for a three stream turbofan engine

Publication Date: 2016.11.29 RTX CORP

AI summary

A gas turbine engine includes a core engine, a first bypass passage disposed about the core engine and a second bypass passage disposed about the first bypass passage. A flow control is disposed within the second bypass for controlling bypass airflow through the second bypass. The flow control translates axially between an open position and a closed position to vary and control airflow through the second bypass passage.