Axially Offset Fuel Plenums Mitigate Combustion Dynamics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current gas turbine combustors with bundled tube fuel nozzles face challenges in mitigating both low and high frequency in-phase combustion dynamics, which can lead to durability issues and limited operability due to coherent instabilities that excite turbine blades.
Innovation Solution
The combustor design features a plurality of bundled tube fuel nozzles with axially offset fuel plenums and premix tubes, allowing for fluid communication through conduits, which mitigates in-phase and coherent combustion dynamics by adjusting the convective time and using predefined axial distances to achieve destructive interference across frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If bundled tube fuel nozzles are used for lean pre-mixed combustion, then combustion efficiency is improved, but combustion dynamics instability occurs at both low and high frequencies
Solution Approach 1:
The fuel nozzle system is segmented into multiple individually controllable bundled tube fuel nozzles arranged annularly, each capable of independent fuel flow modulation. This segmentation allows different nozzles to operate with different phase relationships, disrupting coherent combustion dynamics while maintaining overall combustion efficiency through distributed fuel injection.
Solution Approach 2:
The bundled tube fuel nozzles are positioned asymmetrically relative to the combustor centerline and arranged in non-uniform patterns. This asymmetric configuration prevents symmetric combustion mode excitation and reduces coherent instabilities between adjacent cans, thereby mitigating both low and high frequency combustion dynamics while preserving lean pre-mixed combustion efficiency.
2Speed
If axial modes are excited in the combustor, then low frequency combustion dynamics (200-400 Hz) are generated, but this creates harmful acoustic fields that impact gas turbine components
Solution Approach 1:
The fuel nozzle system incorporates preliminary anti-action by pre-configuring the bundled tube nozzles with specific geometric arrangements and fuel flow characteristics that inherently suppress axial mode excitation. The nozzle design includes features such as optimized fuel injection patterns and premixing lengths that prevent the development of low frequency combustion dynamics before they can generate harmful acoustic fields.
3Productivity
If radial and azimuthal modes are excited, then high frequency screech (greater than 1.0 kHz) occurs, but this excites turbine blades and contributes to high cycle fatigue
Solution Approach 1:
The bundled tube fuel nozzles incorporate local quality variations through different tube diameters, lengths, and fuel port configurations within each nozzle assembly. These local variations create distributed combustion sources with different characteristic frequencies and phases, effectively broadening the combustion response while suppressing coherent high frequency screech that would otherwise excite turbine blades and cause fatigue.
4Quantity of substance
If in-phase combustion dynamics occur between adjacent cans, then coherent instabilities are generated, but these excite turbine blades and limit gas turbine operability
Solution Approach 1:
The fuel nozzle system implements dynamic control capabilities through variable fuel flow regulation for each bundled tube nozzle, allowing the system to adapt fuel distribution patterns in real-time. This dynamic adjustment prevents coherent in-phase combustion dynamics between adjacent cans by introducing phase differences, thereby eliminating turbine blade excitation while maintaining flexible operability across different operating conditions.
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 design effectively reduces adverse effects of combustion dynamics on gas turbine components, enhancing operability by mitigating both low and high frequency instabilities without requiring additional resonators, thus improving the durability and performance of gas turbines.
Implementation Method 1
The first fuel plenum is axially offset at a predefined axial distance from the second fuel plenum with respect to the common axial centerline so as to mitigate in-phase and/or coherent combustion dynamics within the combustor
Data Source
AI summary
A combustor includes a plurality of bundled tube fuel nozzles which are annularly arranged around a common axial centerline. The plurality of bundled tube fuel nozzles comprise a first bundled tube fuel nozzle and a second bundled tube fuel nozzle. The first bundled tube fuel nozzle includes a first fuel plenum and a plurality of premix tubes which extend axially therethrough. The second bundled tube fuel nozzle includes a second fuel plenum and a plurality of premix tubes which extend axially therethrough. The first fuel plenum is axially offset at a predefined axial distance from the second fuel plenum so as to mitigate combustion tones within the combustor. In one embodiment, premix tube fuel ports disposed within the first and/or second fuel plenums may be axially offset with respect to each other within the corresponding fuel plenums at a predefined axial distance to mitigate combustion tones within the combustor.