Reverse Flow Gas Turbine Bypass Valve APU Integration

Solution Overview

Problem

Current auxiliary power units (APUs) in aircraft are considered waste weight as they are seldom used in flight and contribute to increased fuel burn due to their weight, and eliminating them requires a solution to provide ground power and start-up capabilities without additional engines.

Innovation Solution

A reverse flow gas turbine engine design with a bypass valve in the transition duct allows airflow from the engine core to bypass the power turbine, enabling the engine to operate without the power turbine during ground operations, thus eliminating the need for a separate APU.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a separate APU is installed to provide ground power and start-up capabilities, then the required ground support functions are achieved, but the aircraft weight increases and fuel burn increases

Engineering Contradiction:

Improveground power and start-up capabilitiesVSAvoidaircraft weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The gas turbine engine is designed to perform multiple functions: it serves as both the primary propulsion engine during flight and as the APU during ground operations. The bypass valve enables the engine to operate in APU mode by allowing airflow to bypass the power turbine, providing ground power and start-up capabilities without requiring a separate APU unit, thus eliminating the weight penalty of having dedicated APU hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If a separate APU is installed to provide ground power and start-up capabilities, then the required ground support functions are achieved, but fuel burn increases due to the additional weight

Engineering Contradiction:

Improveground power and start-up capabilitiesVSAvoidfuel burn

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The gas turbine engine is designed to perform multiple functions: it serves as both the primary propulsion engine during flight and as the APU during ground operations. The bypass valve enables the engine to operate in APU mode by allowing airflow to bypass the power turbine, providing ground power and start-up capabilities without requiring a separate APU unit, thus eliminating the weight penalty of having dedicated APU hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Weight of moving object

If the APU is eliminated to save weight, then fuel burn decreases, but the ability to provide ground power and start-up capabilities is lost

Engineering Contradiction:

Improveaircraft weightVSAvoidground power and start-up capabilities

Core Design Contradiction:

Weight of moving objectVSAdaptability or versatility

Solution Approach 1:

The gas turbine engine is designed to perform multiple functions: it serves as both the primary propulsion engine during flight and as the APU during ground operations. The bypass valve enables the engine to operate in APU mode by allowing airflow to bypass the power turbine, providing ground power and start-up capabilities without requiring a separate APU unit, thus eliminating the weight penalty of having dedicated APU hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The engine operates in different modes depending on the operational requirements. During ground operations, the bypass valve is opened to allow airflow to bypass the power turbine, enabling APU mode operation for providing ground power and start-up capabilities. During flight, the bypass valve is closed and the engine operates in normal propulsion mode, maximizing the utilization of the core for thrust generation

Inventive Principle:

Principle #15Dynamics

4Weight of moving object

If the APU is eliminated to save weight, then fuel burn decreases, but the engine complexity increases due to the bypass valve system

Engineering Contradiction:

Improveaircraft weightVSAvoidengine complexity

Core Design Contradiction:

Weight of moving objectVSDevice complexity

Solution Approach 1:

The engine operates in different modes depending on the operational requirements. During ground operations, the bypass valve is opened to allow airflow to bypass the power turbine, enabling APU mode operation for providing ground power and start-up capabilities. During flight, the bypass valve is closed and the engine operates in normal propulsion mode, maximizing the utilization of the core for thrust generation

Inventive Principle:

Principle #15Dynamics

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

This design achieves weight savings and increased efficiency by allowing the engine to function as an APU during ground operations, reducing the need for a separate APU and improving fuel efficiency by eliminating unnecessary weight.

Implementation Method 1

a bypass valve in the transition duct that allows air from the engine core to bypass the power turbine

Methodology Applied

Scientific EffectAirflow bypass:

Data Source

PatentUS9726112B2Reverse flow gas turbine engine airflow bypass

Publication Date: 2017.08.08 RTX CORP

AI summary

A gas turbine engine has a propulsor including a fan and a power turbine, an engine core aerodynamically connected to the propulsor by a transition duct, and a bypass valve in the transition duct that allows for air from the engine core to bypass the power turbine.