Orifice Plate Fuel Splitting for Combustion Modal Decoupling
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Solution Overview
Problem
Conventional combustor tuning to reduce sympathetic vibrations in gas turbines imposes unnecessary restrictions and affects the operability and efficiency of combustion systems, leading to undesirable emissions and accelerated wear.
Innovation Solution
The system and method involve varying the combustion instability frequency between combustors by using orifice plates with different effective areas in fuel supply lines to reduce modal coupling, achieved by strategically designing fuel circuits and orifice plates to alter fuel flow rates and pressure ratios, thereby decoupling combustion dynamics frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional combustor tuning is used to reduce sympathetic vibrations, then turbine protection is improved, but combustor operability and thermodynamic efficiency deteriorate
Solution Approach 1:
The invention changes the combustion instability frequency parameter by varying the fuel-to-air ratio in different combustors. By adjusting the equivalence ratio (fuel/air mixture composition) in each combustor, the combustion frequency is shifted away from turbine resonant frequencies, reducing sympathetic vibrations while maintaining optimal combustion efficiency and operability across all combustors
2Reliability
If conventional combustor tuning is used to reduce sympathetic vibrations, then turbine protection is improved, but emissions and component wear deteriorate
Solution Approach 1:
The invention modifies the combustion frequency parameter through fuel-to-air ratio adjustments, which shifts the combustion instability frequency away from turbine resonant frequencies. This reduces the amplitude of sympathetic vibrations, thereby decreasing mechanical stress and wear on turbine components while also improving combustion completeness to reduce harmful emissions
3Object-affected harmful factors
If combustor tuning restrictions are imposed to reduce vibrations, then sympathetic vibrations are reduced, but combustor versatility deteriorates
Solution Approach 1:
The invention changes the operating parameter (fuel-to-air ratio) of each combustor to shift combustion frequencies away from turbine resonant frequencies. This approach provides a flexible, continuous adjustment mechanism that maintains combustor versatility and adaptability across varying operating conditions while effectively reducing sympathetic vibrations, unlike fixed conventional tuning restrictions
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 reduces modal coupling, enhances thermodynamic efficiency, promotes flame stability, and decreases undesirable emissions without harming downstream components, across a range of operating conditions.
Implementation Method 1
strategically designing fuel circuits and orifice plates to alter fuel flow rates and pressure ratios, thereby decoupling combustion dynamics frequencies
Implementation Method 2
each combustor operates at a combustion frequency
Data Source
AI summary
A system and method for reducing modal coupling of combustion dynamics generally include multiple combustors, and each combustor includes multiple fuel nozzle groups for mixing fuel with a compressed working fluid prior to combustion. A fuel circuit is in fluid communication with each fuel nozzle, and orifice plates in the fuel circuit upstream from the fuel nozzles control the fuel split between the fuel nozzles in each combustor and/or between different combustors to produce a frequency difference between combustors.