Combustor Dome Heat Shield Cooling via Staggered Impingement
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Solution Overview
Problem
Combustor heat shields experience thermal mechanical fatigue due to high thermal gradients, leading to cracking and reduced cooling effectiveness, particularly in the radially inner and outer lips exposed to high gas temperatures.
Innovation Solution
An improved cooling scheme is implemented using a combustor with circumferentially arranged rows of impingement and ejecting holes that direct cooling jets against the heat shield lips, with the impingement holes angled to maximize cooling impact and minimize interference between flows, ensuring effective airflow and reduced thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cooling air is directed through impingement holes against the heat shield lips, then cooling effectiveness is improved, but flow interference between impingement and ejecting holes increases
Solution Approach 1:
The patent applies dimensional separation by arranging impingement holes and ejecting holes in different circumferential positions (staggered arrangement) and at different axial locations. The impingement holes are positioned upstream while ejecting holes are positioned downstream, creating spatial separation that reduces flow interference while maintaining effective cooling zones at the heat shield lips.
Solution Approach 2:
The patent implements local quality optimization by providing impingement holes specifically at regions where cooling is most needed (the heat shield lips exposed to highest temperatures), while ejecting holes are positioned to manage flow discharge. This localized approach ensures cooling effectiveness is concentrated where thermal gradients are highest without creating uniform flow interference across the entire structure.
2Temperature
If cooling air is directed through impingement holes at high velocity, then thermal gradient reduction is improved, but flow interference with ejecting holes increases
Solution Approach 1:
The patent uses spatial separation in multiple dimensions - circumferential staggering and axial positioning - to allow high-velocity impingement jets to effectively cool the heat shield lips without their flow paths intersecting with ejecting holes. This dimensional separation enables aggressive cooling where needed while avoiding flow interference that would reduce effectiveness.
Solution Approach 2:
The patent optimizes parameters including the angular orientation of impingement holes, the velocity and pressure of cooling air, and the spatial distribution of holes. By carefully controlling these parameters, the system achieves sufficient cooling velocity to reduce thermal gradients while the staggered arrangement prevents flow interference with ejecting holes.
3Reliability
If heat shield lips are exposed to high gas temperatures, then cooling demand is increased, but thermal mechanical fatigue and cracking increase
Solution Approach 1:
The patent applies preliminary cooling action by directing impingement jets to the heat shield lips before excessive thermal gradients can develop. This proactive cooling approach prevents the buildup of thermal stresses that would lead to thermal mechanical fatigue and cracking, addressing the high cooling demand at the most vulnerable locations.
Solution Approach 2:
The patent provides enhanced cooling specifically at the heat shield lips through impingement holes, while the rest of the heat shield receives different cooling treatment. This localized quality enhancement addresses the highest thermal stress regions without requiring uniform complex cooling across the entire structure, thereby improving fatigue resistance where it is most needed.
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 cooling scheme effectively minimizes thermal gradients, enhances cooling efficiency, and prevents additional damage from high-temperature oxidation while maintaining a smooth airflow, all without increasing cost, weight, or complexity.
Implementation Method 1
directing a first jet of cooling air through a combustor wall and generally normally upon a surface of a peripheral lip of the heat shield
Implementation Method 2
directing a second jet of cooling air through the combustor wall and generally paralelly past the surface of peripheral lip
Data Source
AI summary
A gas turbine engine combustor having a dome heat shield includes a cooling scheme having a plurality of impingement cooling holes extending through the combustor and a plurality of adjacent ejector holes for directing cooling air past the heat shield lips of the dome heat shields. The impingement and ejector holes are preferably staggered to reduce interaction therebetween.