Fuel Nozzle Heat Shield With Thermal-Closing Axial Gap
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional heat shields for fuel injectors in gas turbine engines form gaps due to differential thermal growth, allowing high-temperature gases to ingress and reducing thermal protection effectiveness.
Innovation Solution
A heat shield design that forms an axial gap which decreases in hot conditions relative to cold conditions, reducing high-temperature gas flow by accommodating differential thermal growth between the heat shield and nozzle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional heat shield is used to provide thermal protection, then thermal insulation is improved, but differential thermal growth causes gap formation that allows high-temperature gas ingress and reduces protection effectiveness
Solution Approach 1:
The heat shield is designed to utilize differential thermal expansion between itself and the nozzle/stem assembly. The gap is intentionally configured to close under hot operating conditions when the heat shield expands more than the surrounding components, thereby sealing against high-temperature gas ingress while maintaining thermal insulation effectiveness.
Solution Approach 2:
The gap between the heat shield and nozzle/stem is designed to be dynamic rather than static. The gap dimension changes with temperature, being larger in cold conditions and smaller in hot conditions, allowing the system to adapt to thermal conditions and maintain sealing reliability throughout the operating range.
2Object-affected harmful factors
If the heat shield is positioned close to the nozzle to minimize gas ingress, then thermal protection is improved, but thermal growth may cause contact or binding in hot conditions
Solution Approach 1:
The initial cold-gap dimension is carefully calculated to account for the expected thermal expansion of the heat shield relative to the nozzle and stem. This ensures that the heat shield expands into the gap under hot conditions without causing binding or mechanical interference, while still sufficiently reducing gas ingress pathways.
Solution Approach 2:
The design preemptively compensates for thermal expansion by pre-configuring the gap dimensions in the cold state. This preliminary adjustment prevents the harmful effect of gap opening due to expansion, ensuring the gap closes to seal against gas ingress without causing mechanical binding.
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
Enhances thermal protection of fuel injectors by minimizing high-temperature gas ingress, reducing coking and auto-ignition risks, and maintaining effective thermal insulation across varying operational conditions.
Implementation Method 1
Due to differential thermal growth between the heat shield and fuel injector, conventional heat shields often form a gap that permits ingress of high temperature gases
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An injector (10) includes a mount (14), a stem (16), a nozzle (18), and a heat shield (12). The heat shield (12) extends from the mount (14) to surround the stem (16) and at least a portion of the nozzle (18). The nozzle (18) includes an exterior annular body (24). The distal end of the heat shield (12) is spaced from a lip (26) extending from the exterior annular body (24) or a cap (28) surrounding the nozzle (18) to form an axial gap (G).