Combustor Dome Heat Shield Cooling Air Gap
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Solution Overview
Problem
Existing heat shields in gas turbine engines face challenges in efficiently managing coolant usage to reduce smoke, unburned hydrocarbon, and CO/NOx emissions while maintaining combustion efficiency, as they are exposed to hot gases and require improved cooling schemes.
Innovation Solution
A heat shield design featuring an air gap with nozzle openings, an annular array of effusion holes, and fins to enhance cooling by directing and reusing impingement air for both impingement and effusion cooling, minimizing the amount of coolant needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If more coolant is used to cool the heat shield, then the heat shield temperature is reduced, but the combustion efficiency decreases and emissions increase
Solution Approach 1:
The heat shield employs different cooling methods for different regions: impingement cooling with directed jets for high-heat-flux areas and effusion cooling through distributed holes for other areas. This localized approach optimizes cooling effectiveness while minimizing overall coolant consumption, thereby maintaining combustion efficiency.
Solution Approach 2:
The effusion cooling mechanism utilizes a porous-like structure with numerous small holes distributed across the heat shield surface. Cooling air passes through these holes to provide uniform cooling, achieving effective temperature control with reduced coolant requirements compared to traditional full-surface impingement cooling.
2Loss of energy
If coolant flow is increased to improve heat shield cooling, then heat transfer increases, but smoke and unburned hydrocarbon emissions increase
Solution Approach 1:
The cooling system is segmented into distinct impingement and effusion zones, each handling specific portions of the heat shield cooling requirements. This segmentation allows optimized coolant distribution, ensuring adequate heat transfer while minimizing excess coolant that would otherwise contribute to smoke and unburned hydrocarbon emissions.
Solution Approach 2:
The system changes the parameters of coolant delivery by using high-velocity impingement jets in critical areas and lower-velocity effusion flow in other areas. This parameter variation optimizes heat transfer efficiency while controlling the total coolant quantity to reduce harmful emissions.
3Object-affected harmful factors
If coolant flow is increased to reduce CO/NOx emissions, then heat shield cooling improves, but combustion efficiency decreases
Solution Approach 1:
The heat shield employs different cooling methods for different regions: impingement cooling with directed jets for high-heat-flux areas and effusion cooling through distributed holes for other areas. This localized approach optimizes cooling effectiveness while minimizing overall coolant consumption, thereby maintaining combustion efficiency.
Solution Approach 2:
Instead of applying uniform excessive cooling across the entire heat shield, the system applies partial cooling only where thermally required. The impingement cooling is concentrated on high-heat-flux regions, while effusion cooling provides supplementary cooling elsewhere, avoiding the excessive coolant usage that would harm combustion efficiency.
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 improves heat transfer and reduces coolant requirements by efficiently directing and utilizing cooling air through effusion holes and fins, thereby enhancing combustion efficiency and reducing emissions.
Implementation Method 1
an annular array of effusion holes adjacent the nozzle opening boss, the effusion holes extending through the heat shield and configured to pass cooling air from the back face to a front face of the heat shield
Implementation Method 2
fins interspersed between the effusion holes on the back side of the heat shield
Implementation Method 3
a back face of the heat shield body in spaced-apart facing relationship with the combustor shell to define an air gap between the heat shield body and the combustor shell
Implementation Method 4
recuperating impingent air directed over an impingement cooled region of the heat shield
Data Source
AI summary
A combustor heat shield comprises a heat shield body adapted to be mounted to a combustor wall with a back side of the heat shield body in spaced-apart facing relationship with the combustor wall to define an air gap between the heat shield body and the combustor wall. At least one nozzle opening is defined in the heat shield bod. The opening is bordered by a nozzle opening boss. The boss extends from the back side of the heat shield body across the air gap for sealing engagement with an adjacent part of the combustor. An annular array of effusion holes is provided adjacent the nozzle opening boss. The effusion holes extend through the heat shield body for passing cooling air from the back side to a front side of the heat shield body. Fins are interspersed between the effusion holes on the back side of the heat shield.