Combustor Cap Assembly Cooling and Mixing
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Solution Overview
Problem
Current combustor designs face high thermal stresses on cap assembly components due to high temperatures, leading to decreased turbine efficiency and increased NOx and CO2 generation, as the compressed working fluid used for cooling often enters the combustion zone unmixed with the fuel.
Innovation Solution
A combustor design featuring a shroud with inlet and outlet ports and a sleeve surrounding the fuel nozzle passage, where a cooling medium flows through the inlet passage, cools the cap assembly, and then mixes with the compressed working fluid before entering the combustion zone, ensuring better pre-mixing and reducing unmixed working fluid entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If effusion cooling is used to cool the cap assembly, then thermal stresses on the cap plate are reduced, but the compressed working fluid enters the combustion zone unmixed with the fuel, exacerbating NOx and CO2 generation
Solution Approach 1:
The patent introduces an intermediary mixing zone between the cooling fluid injection point and the combustion zone. The cooling fluid first mixes with the fuel-air mixture in this intermediate region before entering the combustion zone, ensuring proper premixing. This resolves the contradiction by allowing effusion cooling to protect the cap plate while preventing unmixed cooling fluid from entering the combustion zone and causing harmful emissions.
Solution Approach 2:
The patent performs preliminary mixing of the cooling fluid with the fuel-air mixture before the mixture enters the combustion zone. By pre-mixing the cooling fluid with the fuel and air in advance, the system ensures that when the cooling fluid enters the combustion zone, it is already properly mixed, preventing NOx and CO2 generation while maintaining the thermal protection of the cap plate.
2Power
If high temperatures are used in the combustor to increase turbine efficiency, then energy output increases, but thermal stresses on cap assembly components increase
Solution Approach 1:
The patent extracts the thermal protection function from the cap plate structure itself and provides it through a separate cooling fluid delivery system. By introducing cooling fluid through effusion holes in the cap plate, the system separates the high-temperature combustion function from the structural integrity requirement, allowing the cap plate to withstand high temperatures without excessive thermal stress while maintaining turbine efficiency.
Solution Approach 2:
The patent changes the thermal parameters of the cap plate by introducing cooling fluid that reduces the plate temperature. This parameter change allows the cap plate to operate at lower temperatures despite the high-temperature combustion environment, reducing thermal stresses while maintaining the overall high temperature operation needed for turbine efficiency.
3Temperature
If cooling air is directed to impinge against the bluff face, then cooling effectiveness increases, but the spent cooling air flows back towards the air swirler and mixes with fuel-air mixture, potentially affecting combustion
Solution Approach 1:
The patent changes the spatial arrangement by directing cooling fluid through effusion holes in the cap plate into the fuel-air mixture flow path, rather than allowing it to flow back towards the air swirler. This dimensional repositioning ensures that the cooling fluid mixes with the fuel-air mixture in a controlled manner downstream, maintaining proper mixture composition while achieving effective cooling of the cap plate.
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 turbine efficiency by reducing NOx and CO2 generation through improved mixing of the cooling medium with the compressed working fluid, thereby mitigating thermal stresses and increasing the mechanical life of the cap assembly.
Implementation Method 1
directing a portion of the compressed working fluid to the cap assembly and through multiple cooling holes which extend through the cap plate surface
Implementation Method 2
the compressed working fluid flowing through the multiple cooling holes may enter the combustion zone generally unmixed with the fuel
Implementation Method 3
A first fluid flow path may be generally defined from the at least one inlet passage of the first shroud and the at least one inlet port of the first plate
Data Source
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AI summary
A combustor (10) generally includes a shroud (46) that that defines at least one inlet passage (48) extending circumferentially inside the combustor (10). A first plate (50) extends radially inside the shroud (46) downstream from the inlet passage (48). The first plate (50) defines at least one inlet port (56), at least one outlet port (58) and at least partially defines at least one fuel nozzle passage (92). The shroud (46) at least partially surrounds a sleeve (98) that extends around the fuel nozzle passage (92). A tube (102) at least partially surrounded by the sleeve (98) may extend through the fuel nozzle passage (92). The tube (102), the sleeve (98), and the first plate (50) may at least partially define an outlet passage (128). A first fluid flow path (122) generally extends from the at inlet passage (48) to the inlet port (56), and a second fluid flow path (130) extends generally from the outlet port (56) to the outlet passage (128).