Non-uniform Fuel Injection for Reheat Combustor Pulsation Control
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Solution Overview
Problem
Gas turbines with sequential combustion cycles experience thermoacoustic pulsations in the reheat combustor, which restrict operational flexibility and increase NOx emissions, despite efforts to reduce these emissions and enhance efficiency.
Innovation Solution
A method of controlling fuel injection by distributing fuel to injection nozzles in a non-uniform pattern, with higher fuel supply rates to external units for propagation-stabilized flame regions and lower rates to central units for auto-ignition stabilized regions, using integrated mixing devices like vortex generators or undulated profiles to stabilize the flame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If uniform fuel distribution is used in reheat combustor injection nozzles, then operational simplicity is maintained, but thermoacoustic pulsations occur and operational flexibility is restricted
Solution Approach 1:
The patent applies local quality by distributing fuel non-uniformly across different injection nozzles based on their location. External injection units (at the periphery) receive different fuel supply rates compared to central injection units, creating localized fuel enrichment or depletion zones that stabilize the flame and reduce thermoacoustic pulsations while maintaining operational flexibility
Solution Approach 2:
The injection system is segmented into multiple independent injection units with individually controllable fuel supply rates. This segmentation allows the control system to adjust fuel distribution patterns dynamically based on operating conditions, enabling suppression of thermoacoustic pulsations without sacrificing operational adaptability
2Productivity
If high turbine inlet temperature is used to achieve high efficiency, then power generation efficiency is improved, but NOx emissions increase
Solution Approach 1:
The patent creates local fuel-rich and fuel-lean zones through non-uniform fuel distribution to different injection nozzles. This local quality variation enables controlled combustion zones that maintain high turbine inlet temperatures for efficiency while reducing peak temperatures that generate NOx emissions, thus resolving the contradiction between productivity and harmful emissions
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 approach effectively reduces thermoacoustic pulsations without increasing NOx emissions, improving operational flexibility and stability of the gas turbine.
Implementation Method 1
The mixing devices can be constituted by vortex generators in the form of triangular appendices extending from the sides of the injection units upstream from each nozzle
Implementation Method 2
integrated mixing devices configured for mixing the injected fuel with the passing hot gas flow
Data Source
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AI summary
A method is disclosed for controlling fuel injection in a reheat combustor (16) of a gas turbine combustor assembly (3) including a combustor casing (20) defining a gas flow channel (21) and a plurality of injection nozzles (30) distributed in or around the gas flow channel; the method includes the step of distributing fuel among the injection nozzles (30) according to a non-uniform distribution pattern.