Combustor Cap Assembly Cooling Air Recirculation
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Solution Overview
Problem
Current combustor cap plate cooling methods using compressed air that enters unmixed with fuel exacerbate NOx emissions and decrease turbine efficiency, as they do not effectively recirculate cooling air for premixing with fuel before combustion.
Innovation Solution
A combustor cap assembly design incorporating an impingement plate, annular shroud, and flow conditioning plate that recirculates cooling air through a cooling air plenum, allowing it to be premixed with fuel before combustion, utilizing impingement cooling and flow conditioning passages to enhance mixing and reduce thermal stresses on the cap plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If compressed air is routed through cooling holes in the cap plate, then the cap plate is cooled effectively, but the compressed air enters the combustion chamber unmixed with fuel, exacerbating NOx emissions and decreasing turbine efficiency
Solution Approach 1:
The invention recovers the cooling air after it has performed its cooling function by routing it through a plenum chamber back to the combustion chamber inlet, where it is remixed with fuel and reused for combustion, thus eliminating waste and improving efficiency
Solution Approach 2:
The invention merges the cooling air flow path with the fuel air mix path by routing cooled air through a plenum chamber that discharges into the combustion chamber inlet, combining the previously separate cooling and combustion air streams
2Temperature
If compressed air is routed through cooling holes in the cap plate, then the cap plate is cooled effectively, but turbine efficiency decreases due to loss of compressed air that could be used for combustion
Solution Approach 1:
The invention recovers the cooling air after it has performed its cooling function by routing it through a plenum chamber back to the combustion chamber inlet, where it is remixed with fuel and reused for combustion, thus eliminating waste and improving efficiency
3Temperature
If compressed air is routed through cooling holes in the cap plate, then cooling is provided, but the air flow creates thermal stresses on the cap plate
Solution Approach 1:
The invention applies preliminary cooling action by routing compressed air through impingement holes in the impingement plate that directs cooling air onto the upstream side of the cap plate before the air enters the combustion chamber, pre-cooling the cap plate to reduce thermal gradients and stresses
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
The recirculation of cooling air improves turbine efficiency by reducing NOx emissions and thermal stresses on the cap plate, while maintaining effective cooling, thus enhancing overall combustion performance.
Implementation Method 1
The cooling air passage provides for cooling air flow through the flow conditioning plate into the cooling air plenum
Implementation Method 2
utilizing impingement cooling and flow conditioning passages to enhance mixing and reduce thermal stresses on the cap plate
Implementation Method 3
The recirculation of cooling air improves turbine efficiency by reducing NOx emissions and thermal stresses on the cap plate, while maintaining effective cooling
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 to form an impingement air plenum therebetween. The combustor cap assembly further includes a flow conditioning plate 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. The annular portion defines a plurality of flow conditioning passages. The inner band portion at least partially defines a cooling air plenum within the combustor cap assembly. The inner band portion defines an exhaust channel which is in fluid communication with the impingement air plenum and an exhaust outlet. The flow conditioning plate further defines a cooling air passage which provides for cooling air flow into the cooling air plenum.