Pilot Nozzle Combustor Flame Stability and NOx Reduction
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Solution Overview
Problem
Conventional gas turbine combustors with pilot nozzles and main nozzles face instability and high NOx emissions due to unstable combustion and insufficient low-speed flame-stabilizing zones, leading to energy inefficiencies and potential flashback issues.
Innovation Solution
The combustor design incorporates a pilot nozzle with a tapered pilot cone and pilot swirls, where the fuel is injected at a specific angle and position to enhance flame stability, and includes a bypass pipe and flame-stability-enhancing fuel supply channels to create a larger low-speed flame-stabilizing zone and prevent stagnant areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a pilot nozzle is equipped to perform diffusion combustion, then combustion stability is improved, but NOx emissions increase due to high temperature combustion
Solution Approach 1:
The fuel supply is segmented into multiple channels: a first fuel supply channel supplies fuel to the pilot nozzle for diffusion combustion to ensure stability, while a second fuel supply channel supplies fuel to flame-stability-enhancing injection ports that inject fuel into the low-speed flame-stabilizing zone. This segmentation allows different fuel streams to serve different functions, maintaining combustion stability while controlling NOx emissions through optimized fuel distribution.
Solution Approach 2:
The invention creates a localized low-speed flame-stabilizing zone by injecting fuel at specific positions and angles into this zone. The flame-stability-enhancing fuel supply channel targets specifically the low-speed flame-stabilizing zone, creating a localized region with optimized flow characteristics that enhances flame stability without requiring high-temperature diffusion combustion throughout the entire combustor, thereby reducing NOx emissions.
2Stability of the object's composition
If the pilot cone tip projects toward the main burners to form a low-speed flame-stabilizing zone, then flame stability is improved, but stagnant areas are created that may cause flashback
Solution Approach 1:
The invention pre-forms a low-speed flame-stabilizing zone by injecting fuel through the flame-stability-enhancing injection ports into this zone before the main combustion process. This preliminary action creates a controlled low-speed region that stabilizes the flame without requiring the pilot cone tip to project far toward the main burners, thereby preventing stagnant areas and flashback while maintaining flame stability.
3Object-generated harmful factors
If premixed combustion is used in main nozzles, then NOx emissions are reduced, but combustion stability deteriorates causing combustion vibrations
Solution Approach 1:
The invention merges two combustion modes: diffusion combustion in the pilot nozzle for stability and premixed combustion in the main nozzles for low NOx emissions. Additionally, it combines fuel supply from two different channels into the same combustion zone, integrating the stabilizing effect of diffusion combustion with the emission benefits of premixed combustion to achieve both stability and low emissions simultaneously.
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 stabilizes combustion, reduces NOx emissions, and prevents flashback by ensuring efficient fuel distribution and mixing, thereby improving energy efficiency and combustion stability even at lower pilot fuel ratios.
Implementation Method 1
pilot swirls 6 are installed around the tip portion of the pilot nozzle 2, and main swirls 7 are installed around the tip portions of the main nozzles 3
Implementation Method 2
the fuel which is to be injected by the pilot nozzle 2 will be referred as 'pilot fuel' hereinafter. Additionally, the air which is to be supplied to the surrounding area of the pilot nozzle 2 by way of the combustor main body 1 ('pilot air') flows along the inner wall of the pilot cone 4 after passing through the pilot swirls 6
Implementation Method 3
a pilot nozzle 2 which is inserted into the center thereof... a pilot nozzle 2 which diffuses and burns the fuel (diffusion combustion)... the outer circumference of the tip of the pilot nozzle 2 has a plurality of fuel injection ports 21 installed so as to diffuse and inject the fuel
Implementation Method 4
a combustor which performs combustion behavior in order to rotate the gas turbine... the pilot fuel being diffused and injected by the pilot nozzle 2 burns, forming diffusion flame (F)... the main fuel and the main air being mixed by the main burners 5 flow out. When an air-fuel pre-mixture which is a mixture of the main air and the main fuel flows out from the main burners 5, the air-fuel pre-mixture is burned
Data Source
AI summary
Pilot fuel injected from fuel injection ports 21 of a pilot nozzle 2 bumps against an inner wall surface of a tapered portion of an inner circumference of a cone 41 of a pilot cone 4. At this time, the position where a pilot fuel from the fuel injection ports 21 hits is located in a range from a middle of the tapered portion of the inner circumference of a cone 41 to a downstream-side tip thereof.