Combustor Transition Side Wall Extension Decoupling
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Solution Overview
Problem
Gas turbines with can combustors experience dynamic thermo acoustic coupling, leading to strong low-frequency pulsations that negatively affect stability and lifetime, and existing solutions like dampers or fuel staging have drawbacks such as large volume requirements or detrimental emission impacts.
Innovation Solution
A combustor transition with a wall extension that decouples thermo acoustic interactions via the turbine inlet, forming an annular flow path and optionally including a cooling channel, to guide combustion gases and reduce acoustic coupling without the need for staging or dampers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dampers or resonators are installed to mitigate thermo acoustic pulsations, then the pulsations are reduced, but large volumes are required which is not favorable
Solution Approach 1:
The invention extracts the harmful thermo acoustic coupling by removing the connection path between adjacent combustors at the turbine inlet. The side wall extension acts as a physical barrier that separates the flow fields of neighboring combustors, eliminating the coupling mechanism rather than adding damping elements within the combustors themselves.
Solution Approach 2:
The side wall extension serves as an intermediary structure inserted into the turbine inlet flow path. This intermediate element blocks the direct acoustic communication between combustors while maintaining the overall gas flow path, acting as a decoupling barrier without requiring large-volume dampers inside the combustors.
2Reliability
If fuel staging is performed to reduce thermo acoustic pulsations, then the pulsations are mitigated, but emission performance deteriorates due to local hot spots and cold spots
Solution Approach 1:
The invention removes the thermo acoustic coupling mechanism by blocking the acoustic path at the turbine inlet with side wall extensions. This eliminates the need for fuel staging interventions, allowing uniform fuel distribution to be maintained throughout the combustor, thereby avoiding local hot spots and cold spots that generate harmful emissions.
3Measurement precision
If full engine tests are performed to detect unstable modes with can-to-can interaction, then the pulsations can be detected, but the detection occurs rather late in the development process
Solution Approach 1:
The side wall extension is designed and installed in advance during the combustor manufacturing stage, providing preliminary decoupling protection before the combustor is put into operation. This preliminary structural modification prevents the development of thermo acoustic instabilities rather than requiring late-stage detection and correction through full engine tests.
4Reliability
If dampers or resonators are provided to reduce pulsations, then the thermo acoustic interactions are reduced, but tuning is required in late development stage or during commissioning
Solution Approach 1:
The side wall extension provides passive, self-service decoupling functionality through its fixed geometric structure. The extensions automatically block the acoustic coupling paths between combustors without requiring any active tuning, adjustment, or commissioning procedures. The decoupling effect is inherent to the structure itself and remains effective across 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 solution effectively reduces thermo acoustic pulsations, increasing the lifetime of gas turbines and minimizing emissions by decoupling adjacent combustors through the turbine inlet, while allowing for streamlined design and inspection access.
Implementation Method 1
the side wall extension reaches into the flow channel of the turbine inlet thereby decoupling the thermo acoustic interaction between can combustors via the turbine inlet
Implementation Method 2
The side wall extension comprises a cooling channel
Data Source
Figure 1a~1b
Figure 2~3
Figure 4a
AI summary
The disclosure relates combustor transition (24) adapted to guide combustion gases in a hot gas flow path (15) extending between a can combustor (2) and a first stage of turbine (3) in a gas turbine (9). The combustor transition (24) comprises a duct having an upstream end adapted for connection to the can combustor (2) and an downstream end adapted for connection to a first stage of a turbine (3), wherein the downstream end comprises an outer wall (11), an inner wall (12), a first and a second side wall (21a, 21b). The combustor transition is, characterized in that at least one side wall (21a, 21b) has a side wall extension (20, 20a, 20b), which is extending in a downstream direction beyond the outlet (22). Besides the combustor transition (24) a gas turbine comprising such a combustor transition (24), a method for retrofitting a gas turbine (9) with such a combustor transition (24) as well as a method for borescope inspection of a GT with such a combustor transition are disclosed.