Gas Turbine Combustor Flashback Suppression via Inert Gas Purging

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Solution Overview

Problem

Premixed gas turbine combustors face instability issues, including combustion dynamics and flashback, due to fuel-lean mixtures, which can lead to significant damage and reduced engine performance, and existing methods to enhance flashback margin result in high combustion pressure drops and efficiency deterioration.

Innovation Solution

Incorporating an inert gas, such as nitrogen, into the combustor boundary layer to prevent combustion reactions and maintain flashback margin without impacting engine performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If fuel-lean mixtures are used to achieve lowest emissions, then emissions are reduced, but combustion stability deteriorates and pressure fluctuations increase

Engineering Contradiction:

ImproveemissionsVSAvoidcombustion stability

Core Design Contradiction:

Object-generated harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by creating a non-uniform flow structure within the combustor. A central low-swirl region provides stable combustion for fuel-lean mixtures, while an outer high-swirl region enhances mixing and stability. This radial variation in flow characteristics allows the combustor to maintain stability with fuel-lean mixtures without increasing emissions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs dynamic flow control through adjustable swirl generators that can modify the swirl intensity and flow distribution. This dynamic capability allows optimization of combustion stability and emissions control under varying operating conditions, maintaining stable combustion with fuel-lean mixtures across different load conditions

Inventive Principle:

Principle #15Dynamics

2Reliability

If flashback margin is increased by ensuring bulk fuel/air velocity exceeds flame speed, then flashback is prevented, but combustion pressure drop increases and engine efficiency deteriorates

Engineering Contradiction:

Improveflashback marginVSAvoidcombustion pressure drop

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent segments the combustor flow into distinct regions with different flow characteristics. The central low-swirl region and outer high-swirl region create zones with different velocity profiles and flame propagation characteristics. This segmentation allows flashback prevention in critical areas without requiring excessively high bulk velocities throughout the entire combustor, thereby reducing overall pressure drop

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary zone between the premixer and combustion chamber where flow characteristics are gradually modified. This transition region acts as a buffer that prevents direct flame propagation upstream while maintaining reasonable pressure drop, serving as an intermediary that protects against flashback without the need for extremely high velocities

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If fuel content is increased to stabilize flame, then combustion stability improves, but emissions increase

Engineering Contradiction:

Improveflame stabilityVSAvoidemissions

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent creates local quality variations through the dual-swirl structure where different regions have different fuel-air ratios and flow characteristics. The central region can operate with fuel-lean mixtures for low emissions while the outer region provides enhanced mixing and stability, allowing the system to achieve flame stability without uniformly increasing fuel content and thereby controlling emissions

Inventive Principle:

Principle #3Local quality

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 inert gas purging of the boundary layer effectively prevents flame flashback, enhancing stability and reducing the risk of damage while maintaining engine efficiency by ensuring no combustion occurs in the boundary layer, thus improving flashback margin.

Implementation Method 1

Purging the boundary layer with an inert gas will prevent a combustible reaction from occurring and being sustained in the boundary layer should a flashback occur

Methodology Applied

Scientific EffectInert gas purging:

Implementation Method 2

premix combustion, where fuel and compressed air are mixed together prior to ignition to form as homogeneous a mixture as possible

Methodology Applied

Scientific EffectPremixing:

Implementation Method 3

fuel and compressed air are mixed together and ignited to produce hot combustion gases that drive a turbine

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS7513115B2Flashback suppression system for a gas turbine combustor

Publication Date: 2009.04.07 H2 IP UK LTD

AI summary

A gas turbine combustor having improved flashback margin is disclosed. Multiple embodiments of the present invention are disclosed including combustors having a single premix chamber as well as multiple premix chambers. Flashback margin is increased for the combustor by incorporating a means for introducing an inert gas, such as nitrogen, into the premix chamber(s) at the region proximate the boundary layer to purge the boundary layer of combustible mixture, thereby ensuring that no combustion reaction occurs in the boundary layer.