Fuel Nozzle Projections for Turbine Engine Flashback Mitigation
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Solution Overview
Problem
Known gas turbine engines experience flame holding/flashback events and increased vibrations due to combustion of high hydrogen fuel mixtures, leading to degradation of emissions performance and reduced lifespan of fuel nozzle assemblies.
Innovation Solution
A fuel nozzle design featuring mixing tubes with outwardly extending projections that create a chevron-shaped groove to enhance fuel-air mixing and incorporate a cooling fluid, reducing flame holding/flashback events and screech tone frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high hydrogen fuel mixtures are combusted to improve emissions performance, then fuel efficiency is improved, but flame holding/flashback events occur causing degradation of emissions performance and overheating damage
Solution Approach 1:
The mixing tube outlet is segmented into multiple injection holes instead of a single continuous outlet. This segmentation creates discrete fuel injection points that improve mixing control and reduce flame holding by preventing large-scale recirculation zones that trap flames upstream.
Solution Approach 2:
The injection holes are positioned asymmetrically on the mixing tube outlet surface, with holes located at different radial positions and angles. This asymmetric arrangement disrupts symmetric recirculation patterns that cause flame holding, promoting more uniform fuel-air mixing and reducing flashback susceptibility.
2Power
If high hydrogen fuel mixtures are combusted to improve fuel efficiency, then energy output is improved, but screech tone frequencies cause vibrations that shorten assembly lifespan
Solution Approach 1:
The segmented outlet structure breaks up large coherent vortex structures into smaller, more distributed flow patterns. This reduces the intensity of screech tone frequencies by dispersing the combustion instability sources across multiple injection points rather than concentrating them in a single flow path.
Solution Approach 2:
The asymmetric hole arrangement creates dynamically evolving flow patterns that adapt to combustion conditions. This dynamic flow structure prevents the establishment of fixed, resonant vibration modes that cause screech tones, thereby reducing cyclic thermal and mechanical stresses on the assembly.
3Device complexity
If conventional mixing tubes are used to channel fuel, then device complexity is low, but mixing efficiency is insufficient leading to flame holding events
Solution Approach 1:
The mixing tube outlet is divided into multiple injection holes, creating a segmented structure that enhances fuel-air mixing by distributing fuel injection across multiple points. This segmentation promotes better mixing efficiency while maintaining relatively simple manufacturing through standard drilling and tapping operations.
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 improves mixing efficiency, reduces flame holding/flashback events, and decreases undesirable vibrations, thereby extending the lifespan of the fuel nozzle assembly and enhancing the overall performance of the turbine engine.
Implementation Method 1
A plurality of mixing tubes extends through the housing for channeling fuel to the combustion chamber
Implementation Method 2
Adjacent projections are spaced a circumferential distance apart such that a groove is defined between each pair of circumferentially-apart projections to facilitate enhanced mixing of fuel in the combustion chamber
Data Source
AI summary
A fuel nozzle for use with a turbine engine is described herein. The fuel nozzle includes a housing that is coupled to a combustor liner defining a combustion chamber. The housing includes an endwall that at least partially defines the combustion chamber. A plurality of mixing tubes extends through the housing for channeling fuel to the combustion chamber. Each mixing tube of the plurality of mixing tubes includes an inner surface that extends between an inlet portion and an outlet portion. The outlet portion is oriented adjacent the housing endwall. At least one of the plurality of mixing tubes includes a plurality of projections that extend outwardly from the outlet portion. Adjacent projections are spaced a circumferential distance apart such that a groove is defined between each pair of circumferentially-apart projections to facilitate enhanced mixing of fuel in the combustion chamber.