Premix Fuel Nozzle Assembly Pilot Flame Stabilization
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Solution Overview
Problem
Existing fuel nozzle assemblies for gas turbines with gas-only cartridges face challenges in maintaining pilot flame stability due to strong air jets and high temperature environments, which can lead to undesirable fluctuations in heat release and instability.
Innovation Solution
The fuel nozzle assembly incorporates a cartridge with a curvilinear downstream radial wall and angled injection ports to create a swirling air flow that provides convection cooling and a protective film over the cartridge and premix pilot nozzle, stabilizing the pilot flame by reducing the impact of purge air on the flame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a gas only cartridge is used in the fuel nozzle assembly, then the nozzle can operate in gas-only mode, but the cartridge exit face is exposed to extremely high temperatures and strong air jets that destabilize the pilot flame
Solution Approach 1:
A cooling air film is introduced as an intermediary layer between the cartridge exit face and the pilot flame. This cooling air film serves as a mediator that stabilizes the pilot flame by reducing the direct impact of hot combustion gases and strong air jets from the cartridge, while still allowing the gas-only operating mode to function.
Solution Approach 2:
The strong air jets and high temperatures that were harmful to pilot flame stability are converted into beneficial cooling effects. The cooling air film utilizes the temperature differential between the cold cartridge and hot combustion gases to create a stable thermal boundary layer that protects the pilot flame, transforming the harmful thermal environment into a stabilizing mechanism.
2Temperature
If the cartridge exit face is exposed to hot combustion gases, then cooling is required to prevent damage, but cooling air jets can cause pilot flame instability
Solution Approach 1:
The cooling function is localized to specific regions where it is most needed. The cooling air film is directed to form primarily at the cartridge exit face and along the premix pilot nozzle, providing localized cooling protection in these high-temperature zones while minimizing the disruptive effect on the overall pilot flame stability.
Solution Approach 2:
The cooling air film creates a curved or layered flow pattern that follows the contours of the cartridge and nozzle surfaces. This curved flow structure helps to stabilize the pilot flame by creating a more uniform thermal environment compared to direct linear air jets, reducing turbulence and flame instability.
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 enhances pilot flame stability and reduces instability issues by creating a cooling air film that protects the exit faces of the nozzle and cartridge, improving operational reliability and efficiency.
Implementation Method 1
purge air flowing from the cartridge may negatively impact pilot flame stability... providing cooling to the exit faces of the premix pilot nozzle and/or the gas only cartridge
Implementation Method 2
create a swirling air flow that provides convection cooling and a protective film over the cartridge and premix pilot nozzle
Data Source
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AI summary
A fuel nozzle assembly 100 includes a centerbody 102 and a cartridge 200 that extends axially through the centerbody 102. The cartridge 200 defines a purge air passage 204 within the centerbody 102. The cartridge 200 includes a tip portion 202 that is defined by a tip body 206. The tip body 206 defines a throat portion 208 and a mouth portion 210 which is defined downstream from the throat portion 208. The tip body 206 further defines a plurality of injection ports 218 circumferentially spaced around the throat portion 208. The injection ports 218 provide for fluid communication between the purge air passage 204 and the throat portion 208 of the tip body 206.