Combustor Cap Assembly Premixed Cooling Air
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Solution Overview
Problem
Existing combustor designs exacerbate NOx emissions and decrease turbine efficiency due to compressed air used for cooling the cap plate being unmixed with fuel during effusion cooling.
Innovation Solution
A combustor cap assembly that recirculates cooling air through an impingement air plenum, allowing it to be premixed with fuel before combustion, utilizing a flow conditioning plate with annular and band portions to facilitate fluid communication and mixing within an annular flow passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If compressed air is routed through cooling holes in the cap plate using effusion cooling, then the cap plate is cooled effectively, but the cooling air enters the combustion chamber unmixed with fuel, exacerbating NOx emissions and decreasing turbine efficiency
Solution Approach 1:
The invention merges the cooling air flow path with the fuel mixing path by routing the cooling air through the impingement air plenum where it mixes with fuel before entering the combustion chamber. This combines the cooling function with the fuel-air mixing function, allowing the cooling air to perform dual purposes: cooling the cap plate and participating in combustion as premixed air-fuel mixture.
Solution Approach 2:
The impingement air plenum serves as an intermediary chamber between the cooling holes and the combustion chamber. Instead of allowing cooling air to enter the combustion chamber directly (unmixed), the plenum provides a intermediate space where fuel can be introduced and mixed with the cooling air, creating a premixed air-fuel mixture before combustion occurs.
2Temperature
If compressed air is routed through cooling holes in the cap plate, then cooling is achieved, but turbine efficiency decreases due to unmixed air entering the combustion chamber
Solution Approach 1:
The invention merges the cooling air flow path with the fuel mixing path by routing the cooling air through the impingement air plenum where it mixes with fuel before entering the combustion chamber. This combines the cooling function with the fuel-air mixing function, allowing the cooling air to perform dual purposes: cooling the cap plate and participating in combustion as premixed air-fuel mixture.
Solution Approach 2:
The impingement air plenum serves as an intermediary chamber between the cooling holes and the combustion chamber. Instead of allowing cooling air to enter the combustion chamber directly (unmixed), the plenum provides a intermediate space where fuel can be introduced and mixed with the cooling air, creating a premixed air-fuel mixture before combustion occurs.
3Temperature
If effusion cooling is used with multiple cooling holes, then the cap plate is cooled, but the cooling air remains separate from the fuel stream, worsening emissions
Solution Approach 1:
The invention merges the cooling air flow path with the fuel mixing path by routing the cooling air through the impingement air plenum where it mixes with fuel before entering the combustion chamber. This combines the cooling function with the fuel-air mixing function, allowing the cooling air to perform dual purposes: cooling the cap plate and participating in combustion as premixed air-fuel mixture.
Solution Approach 2:
The impingement air plenum serves as an intermediary chamber between the cooling holes and the combustion chamber. Instead of allowing cooling air to enter the combustion chamber directly (unmixed), the plenum provides a intermediate space where fuel can be introduced and mixed with the cooling air, creating a premixed air-fuel mixture before combustion occurs.
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 NOx emissions and enhances turbine efficiency by ensuring the cooling air is premixed with fuel, improving the thermal management of the cap plate while maintaining or improving cooling efficiency.
Implementation Method 1
The flow conditioning plate includes an inner band portion, an outer band portion and an annular portion which extends radially between the inner and outer band portions. The annular portion includes an upstream side and a downstream side and defines a plurality of flow conditioning passages which provide for fluid communication through the upstream and downstream sides.
Implementation Method 2
A cap plate is coupled to the impingement plate and an impingement air plenum is defined therebetween... effectively reduces NOx emissions and enhances turbine efficiency by ensuring the cooling air is premixed with fuel
Implementation Method 3
One way to cool the cap plate is to route a portion of the compressed air into the cap assembly and onto an upstream side of the cap plate. The compressed air is then routed through multiple cooling holes which extend through the cap plate. This method is known in the industry as effusion cooling.
Implementation Method 4
To increase turbine efficiency, modern combustors are operated at high temperatures which generate high thermal stresses on various mechanical components disposed within the combustor
Data Source
AI summary
A combustor cap assembly includes an impingement plate coupled to an annular shroud and a cap plate which is coupled to the impingement plate and forms an impingement air plenum therebetween. The cap assembly further includes a flow conditioning plate which is coupled to a forward end portion of the shroud. The flow conditioning plate includes an inner band portion, an outer band portion and an annular portion which extends radially therebetween. The annular portion includes upstream side, a downstream side and a plurality of flow conditioning passages which provide for fluid communication through the upstream and downstream sides. The inner band portion of the flow conditioning plate at least partially defines an exhaust channel. The exhaust channel is in fluid communication with the impingement air plenum and an exhaust outlet. The exhaust outlet is positioned to route cooling air from the impingement air plenum into an annular flow passage defined within a combustor.