Heat Shield Effusion Cooling for Combustion Chamber
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Solution Overview
Problem
The curved lips at the radially inner and outer ends of heat shields in combustion chambers suffer from overheating and oxidation due to inadequate cooling, and the coolant supplied is not effectively reducing emissions, with a uniform coolant film on annular walls using more coolant than necessary and heat shields experiencing overheating adjacent to fuel injector apertures.
Innovation Solution
The introduction of multiple circumferentially spaced apertures in the heat shields to direct coolant over the surfaces of the annular walls, forming a film and reducing overheating, with specific aperture configurations and orientations to optimize coolant flow and minimize smoke production, and the removal of curved lips to improve coolant distribution and reduce overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If curved lips are provided at the radially inner and outer ends of heat shields, then the heat shields are spaced from the annular walls, but the curved lips suffer from overheating and oxidation due to inadequate cooling
Solution Approach 1:
The heat shields are provided with effusion cooling apertures distributed across their surfaces, allowing coolant to escape and form a protective cooling film on the outer annular wall structure. This porous approach enables uniform coolant distribution without requiring curved lips, eliminating the overheating and oxidation problem while maintaining proper spacing.
Solution Approach 2:
The curved lips are completely removed from the heat shield design. Instead of providing spacing through protruding lips, the heat shields are positioned at appropriate distances from the annular walls directly, eliminating the problematic component that suffered from inadequate cooling.
2Temperature
If coolant is supplied through apertures in heat shields to cool the lips, then the lips are cooled, but the coolant is not effectively reducing emissions and uses more coolant than necessary
Solution Approach 1:
Coolant is directed to specific areas where it is most needed through strategically positioned effusion cooling apertures. The apertures are distributed to provide cooling where thermal loads are highest, rather than uniformly cooling all surfaces including non-critical areas like curved lips. This localized approach reduces overall coolant consumption while maintaining effective cooling where required.
Solution Approach 2:
The coolant system is designed to reduce emissions by directing cooled air into the combustion chamber to suppress smoke and improve combustion efficiency. The coolant serves dual purposes: cooling the heat shields and reducing harmful emissions, converting a potential waste stream into a beneficial function.
3Temperature
If a uniform film of coolant is formed on the inner and outer annular wall structures, then the walls are cooled, but more coolant is used than required
Solution Approach 1:
The effusion cooling apertures in the heat shields are strategically positioned and sized to create non-uniform coolant distribution patterns. Areas of the annular walls experiencing higher thermal loads receive more coolant, while cooler areas receive less. This localized quality approach maintains effective wall cooling while minimizing overall coolant consumption compared to uniform film formation.
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 solution effectively reduces overheating and oxidation of heat shields, optimizes coolant usage, and minimizes emissions by ensuring sufficient coolant reaches critical areas, improving the thermal management and operational efficiency of the combustion chamber.
Implementation Method 1
Each heat shield has a plurality of apertures arranged circumferentially around the fuel injector aperture and extending there-through to supply coolant from the chamber radially outwardly with respect to the fuel injector aperture to provide effusion cooling of the surface facing away from the upstream wall
Implementation Method 2
The upstream wall has a plurality of apertures to direct coolant onto the curved lips at the radially inner and radially outer ends of the heat shields to provide impingement cooling of the lips
Data Source
AI summary
A combustion chamber comprises an upstream end wall structure and inner and outer annular wall structures. The upstream end wall structure comprises an upstream wall and a plurality of circumferentially arranged heat shields secured to the upstream wall. The upstream wall has a plurality of circumferentially spaced fuel injector apertures. Each heat shield has radially outer and radially inner ends and a fuel injector aperture aligned with a corresponding fuel injector aperture in the upstream wall. The radially outer and inner ends of each heat shield have outer and inner rails spacing the heat shield from the upstream wall. The radially outer and inner ends of each heat shield have first and second pluralities of circumferentially spaced apertures extending there-through and through the associated outer and inner rails to direct coolant over the surface of the outer and inner annular wall structures to form respective films of coolant.