Gas Turbine Augmentor Fuel Injector Positioning

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Solution Overview

Problem

Gas turbine engine augmentors experience high-frequency combustion-induced pressure oscillations known as screech or rumble due to thermo-acoustic coupling, leading to acoustic noise and fatigue damage.

Innovation Solution

Positioning fuel injectors and flame holders in the augmentor such that heat release and acoustic pressure oscillation cycles are out of phase by at least 100 degrees and less than 260 degrees, determined through acoustic and combustion response modeling to reduce thermo-acoustic coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If fuel injectors and flame holders are positioned to maximize heat release, then thrust is improved, but thermo-acoustic coupling increases causing screech and rumble

Engineering Contradiction:

ImprovethrustVSAvoidthermo-acoustic coupling

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent changes the phase relationship parameter between heat release and acoustic pressure oscillations by adjusting the axial positions of fuel injectors and flame holders. Specifically, positioning these components to create a phase difference of 100-260 degrees alters the thermo-acoustic coupling characteristics, reducing screech and rumble while maintaining thrust production.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of moving object

If augmentor operation is continued, then thrust is maintained, but fatigue damage accumulates due to pressure oscillations

Engineering Contradiction:

Improveaugmentor operation durationVSAvoidfatigue resistance

Core Design Contradiction:

Duration of action of moving objectVSStrength

Solution Approach 1:

The patent applies preliminary anti-action by pre-positioning the fuel injectors and flame holders to create out-of-phase heat release and acoustic pressure oscillations. This preliminary configuration prevents the buildup of damaging pressure oscillations before they can cause fatigue damage, allowing sustained augmentor operation without compromising structural integrity.

Inventive Principle:

Principle #9Preliminary anti-action

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 positioning effectively decouples heat release and acoustic pressure oscillations, reducing unwanted noise and fatigue damage by minimizing thermo-acoustic coupling across a range of operating parameters.

Implementation Method 1

screech and rumble are caused by thermo-acoustic coupling, i.e., coupling of the heat release and acoustic pressure oscillation cycles, of an augmentor

Methodology Applied

Scientific EffectThermo-acoustic coupling: Thermoacoustic Effect

Implementation Method 2

flame holders positioned downstream of the fuel injectors and being operative to ignite the fuel dispensed from the fuel injectors

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS9759424B2Systems and methods involving reduced thermo-acoustic coupling of gas turbine engine augmentors

Publication Date: 2017.09.12 RTX CORP

AI summary

A method for providing thermo-acoustic coupling of a gas turbine engine augmentor includes determining acoustic resonances and heat release phase relationships associated with the augmentor. A fuel injector of the augmentor is positioned at an axial position relative to a flame holder of the augmentor in response to the determined acoustic resonances and heat release phase relationships associated with the augmentor. Heat release and acoustic pressure oscillation cycles associated with the augmentor are out of phase by at least approximately 100 degrees.