Combustor End Cap Bracing for Vibration Reduction
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Solution Overview
Problem
Combustors face challenges with vibrations caused by fluid flow, leading to harmful combustion dynamics, reduced component life, and increased emissions, which are not adequately addressed by existing solutions that attempt to prevent harmonic frequencies or adjust geometry.
Innovation Solution
The combustor design includes radially and axially extending supports to brace the end cap, increasing its natural or resonant frequency, thereby reducing vibrations and enhancing mixing efficiency without adversely affecting fuel and working fluid interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the natural or resonant frequency of the end cap is increased to avoid harmonic frequencies and reduce vibrations, then combustion dynamics are stabilized and component life is extended, but the device complexity increases due to additional bracing structures
Solution Approach 1:
The end cap is divided into multiple sections with struts providing localized bracing at specific positions. This segmentation allows the structure to be reinforced where needed to increase natural frequency while maintaining simplicity in other areas, thus stabilizing combustion dynamics without excessive overall complexity
Solution Approach 2:
Struts extend radially and/or axially from the end cap to provide bracing in additional spatial dimensions. This dimensional approach increases the natural frequency of the end cap by adding structural support in directions that were previously uncompensated, thereby reducing vibrations and stabilizing combustion without requiring complete redesign of the entire structure
2Use of energy by moving object
If higher combustion gas temperatures are used to improve thermodynamic efficiency, then energy efficiency increases, but flashback or flame holding conditions occur causing severe damage to nozzles
Solution Approach 1:
The enhanced mixing of working fluid and fuel before combustion creates a more stable flame front that resists migrating upstream toward the nozzles. This preliminary mixing action prevents the harmful flashback effect before it can occur, allowing high combustion temperatures to be maintained safely for improved thermodynamic efficiency
Solution Approach 2:
The combustion system operates with altered parameters including enhanced mixing ratios and controlled fuel-air mixture composition. These parameter changes enable the system to maintain high combustion gas temperatures for efficiency while the modified mixture characteristics prevent flashback by ensuring complete mixing and stable combustion throughout the chamber
3Use of energy by moving object
If higher combustion gas temperatures are used to improve thermodynamic efficiency, then energy efficiency increases, but nitrogen oxides emissions increase due to increased disassociation rate of diatomic nitrogen
Solution Approach 1:
The system changes operational parameters including combustion temperature control and mixture composition to optimize the balance between efficiency and emissions. By carefully controlling the fuel-air ratio and combustion timing, the system maintains high thermodynamic efficiency while limiting peak temperatures to reduce nitrogen oxide formation
Solution Approach 2:
The combustion process utilizes periodic or staged fuel injection and air supply to control temperature profiles. This periodic action allows the system to achieve high efficiency during combustion phases while controlling overall temperature exposure to minimize nitrogen disassociation and subsequent nitrogen oxide 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 extends combustor operating conditions, increases component lifespan, maintains design margins for flashback prevention, and reduces undesirable emissions by stabilizing combustion dynamics and emissions.
Implementation Method 1
one or more supports may extend radially and/or axially from the end cap to brace the end cap against the casing. The additional bracing provided by the supports tends to increase the natural or resonant frequency of the end cap
Implementation Method 2
A plurality of tubes may be radially arranged in the end cap to provide fluid communication through the end cap and into a combustion chamber. A working fluid and fuel are supplied through the tubes to enhance mixing between the working fluid and fuel
Implementation Method 3
Combustors are commonly used in industrial and power generation operations to ignite fuel to produce combustion gases having a high temperature and pressure
Data Source
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AI summary
A combustor (10) includes a casing (12) that surrounds at least a portion of the combustor (10) and includes an end cover (16) at one end of the combustor (10). An end cap (20) axially separated from the end cover (16) is configured to extend radially across at least a portion of the combustor (10) and includes an upstream surface (28) axially separated from a downstream surface (30). A plurality of tubes (34) extends from the upstream surface (28) through the downstream surface (30) to provide fluid communication through the end cap (20). A cap shield (46) extends axially from the end cover (16) and circumferentially surrounds and supports the end cap (20).