Transition Duct Fuel Staging for Combustor Exit Temperature Control
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Solution Overview
Problem
Maintaining high combustion gas temperatures in gas turbines for efficiency often reduces the service life of hot gas path components due to excessive heat exposure.
Innovation Solution
Implementing late lean fuel injection nozzles at the aft end of the transition duct, which inject fuel downstream of the combustion chamber, allowing for more uniform and increased exit temperature profiles without exposing components to peak temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high combustion gas temperatures are maintained for efficiency, then turbine efficiency is improved, but service life of hot gas path components deteriorates
Solution Approach 1:
The fuel injection system is segmented into multiple nozzles positioned at different locations: traditional nozzles at the combustor inlet and additional nozzles at the transition duct aft end. This segmentation allows different zones to serve different functions - the upstream nozzles provide base combustion while the downstream nozzles control the temperature profile at the exit, enabling high average temperatures without concentrating peak heat on component surfaces.
Solution Approach 2:
The temperature distribution along the transition duct is made non-uniform through strategic fuel placement. By injecting fuel at the aft end of the transition duct, the combustion occurs in a specific zone that raises the average exit temperature while the flame positioning and mixing characteristics ensure peak temperatures are distributed away from duct walls, creating a favorable local quality pattern that protects components.
2Device complexity
If fuel is injected at traditional locations, then combustion chamber structure is simple, but exit temperature profile becomes non-uniform with peak temperatures on duct walls
Solution Approach 1:
The fuel injection approach transitions from a single-point or single-zone injection to a distributed multi-zone injection system. By adding nozzles at the transition duct aft end, the combustion process is extended into a new spatial dimension along the duct length, creating a more uniform temperature distribution in the exit plane while avoiding concentration of thermal load on any single location.
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 maintains or increases average exit temperatures while diverting peak temperatures away from duct walls, enhancing component durability and turbine efficiency, leading to longer service life and improved output.
Implementation Method 1
two or more late lean fuel injection nozzles (56, 58) are mounted on the transition duct (18) at its aft end (20)... Fuel is supplied to the injection nozzles (56, 58)... allowing for more uniform and increased exit temperature profiles
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A gas turbine combustor (10) includes a combustion chamber (39) defined by a combustor liner (38), the combustor liner having an upstream end cover (30) supporting one or more nozzles (32) arranged to supply fuel to the combustion chamber where the fuel mixes with air supplied from a compressor. A transition duct (20) is connected between a downstream end of the combustion chamber liner and a first stage turbine nozzle (50, 52, 54) the transition duct supplying gaseous products of combustion to said first stage turbine nozzle. One or more additional fuel injection nozzles (56, 58) is arranged at an aft end of the transition duct (20) for introducing additional fuel and air for combustion into the transition duct (20) upstream of the first stage turbine nozzle.