Annular Collar Cooling via Flow Disturbance Pegs
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Solution Overview
Problem
Conventional fuel injection systems for annular combustion chambers in turbomachines face challenges in effectively reducing the temperature gradient across the annular collar due to thermal radiation, despite the use of thermal barriers, which often do not adequately address the issue.
Innovation Solution
The introduction of pegs or studs on the upstream radial surface of the annular collar to disturb the cooling air flow and increase the heat exchange area, enhancing cooling by both air impact and flow, with pegs distributed in multiple rows and varying dimensions to optimize heat flux and air recirculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermal barrier is provided on the downstream radial surface of the collar, then the temperature of the collar is reduced, but the temperature gradient in the collar is not effectively reduced
Solution Approach 1:
The invention applies different thermal protection measures to different regions of the collar. The downstream radial surface receives thermal barrier protection, while the upstream radial surface is enhanced with cooling air flow disturbance features (protrusions or recesses) to increase local heat exchange. This localized differentiation addresses both temperature reduction and temperature gradient reduction simultaneously.
Solution Approach 2:
The invention transitions from a single-dimension thermal barrier approach to a multi-dimensional solution by adding surface features (protrusions or recesses) that create three-dimensional flow disturbance. This increases the effective heat exchange surface area and improves cooling efficiency without simply increasing the thermal barrier thickness.
2Temperature
If the cooling air flow is disturbed by protrusions or recesses on the upstream radial surface, then the heat exchange area is increased, but the device complexity increases
Solution Approach 1:
The collar surface is segmented into multiple protrusions or recesses distributed in annular rows. This segmentation increases the effective heat exchange surface area and creates multiple flow disturbance points, improving cooling efficiency while maintaining a relatively simple overall structure that can be integrated into the existing collar geometry.
Solution Approach 2:
The invention optimizes parameters such as the number, size, spacing, and depth of the protrusions or recesses to achieve the desired heat exchange enhancement. By carefully selecting these parameters, the design achieves improved cooling efficiency without excessive complexity, balancing performance and manufacturability.
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 increases the heat exchange area by 5% to 10%, effectively reducing the temperature gradient and improving the cooling efficiency of the annular collar, thereby enhancing the overall performance of the fuel injection system.
Implementation Method 1
The collar is cooled by air impacting against its upstream radial surface, the air exiting from orifices formed in the injection system. This air comes against a radially inner portion of the collar and flows radially from the inside towards the outside along the upstream radial surface of the collar in order to cool it.
Implementation Method 2
Because of the abovementioned radiation, a relatively steep temperature gradient appears in the radial direction of the collar, its radially outer portion being hotter than its radially inner portion.
Implementation Method 3
In operation, the abovementioned annular collar of the injection system is subjected to a high level of thermal radiation
Data Source
AI summary
A fuel injection system for an annular combustion chamber of a turbomachine including a support device for supporting and centering a fuel injector head; and a bowl arranged downstream from the support device and including at its downstream end an annular collar that extends radially outwards and that is cooled by air impacting against its upstream radial surface is disclosed. The upstream radial surface includes a device which disturbs the flow of cooling air and increases the heat exchange area between the air and the collar.