Fuel Injector Heat Shield Segmented Support
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Solution Overview
Problem
Fuel injectors in combustion engines face issues with heat transfer from high-temperature compressor air, leading to coke formation, thermal stress, and increased manufacturing costs due to solid support/stem components, which affect performance and durability.
Innovation Solution
A fuel nozzle design featuring a heat shield and multiple cylindrical support members that thermally isolate the fuel tube, reducing heat transfer and internal stresses, and eliminating the need for a solid support/stem, using off-the-shelf components to increase stiffness-to-mass ratio and modal frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid support/stem is used to hold the fuel tube, then structural strength is provided, but heat transfer from compressor air to fuel increases and thermal stresses fatigue the component
Solution Approach 1:
The patent divides the solid support/stem into multiple discrete support members (typically three) that are spaced circumferentially around the fuel tube. This segmentation reduces the continuous thermal conduction path while maintaining structural support, as each support member acts as an independent thermal barrier rather than a continuous heat transfer conduit.
Solution Approach 2:
The patent introduces a thermal barrier layer (insulation material) between the support members and the fuel tube, and/or between the support members and the combustion chamber environment. This intermediary layer acts as a thermal resistance that reduces heat transfer from the high-temperature compressor air to the fuel, while the support members maintain the structural positioning.
2Strength
If a solid support/stem is used, then structural support is provided, but manufacturing costs increase due to expensive tooling and dies
Solution Approach 1:
The solid support/stem is replaced with multiple simple support members that can be manufactured using standard, low-cost processes. These segmented components eliminate the need for expensive custom tooling and dies required for solid support/stem fabrication, while maintaining adequate structural support through their distributed configuration.
Solution Approach 2:
The support members are designed as simple, inexpensive components that can be manufactured using conventional processes without requiring costly tooling. While individually simpler, the collective assembly provides the necessary structural support at reduced manufacturing cost.
3Strength
If a solid support/stem is used, then structural integrity is maintained, but stiffness-to-mass ratio is low resulting in lower modal frequencies
Solution Approach 1:
The continuous solid support/stem is replaced with discrete support members that reduce the overall mass of the assembly. The segmented configuration maintains structural integrity through distributed support points while reducing the mass that contributes to lower modal frequencies, thereby improving the stiffness-to-mass ratio.
4Ease of operation
If a solid support/stem is used, then fuel tube positioning is maintained, but thermal stresses from temperature gradients cause fatigue
Solution Approach 1:
The continuous thermal stress path in a solid support/stem is interrupted by segmenting into discrete support members. This segmentation breaks the thermal stress continuity, allowing each support member to independently accommodate thermal expansion and contraction, thereby reducing cumulative thermal stress fatigue while maintaining fuel tube positioning.
Solution Approach 2:
A thermal barrier or insulation layer is introduced between the support members and the fuel tube, and/or between the support members and the hot environment. This intermediary reduces the temperature gradient across the support structure, minimizing thermal stress and fatigue while still maintaining proper fuel tube positioning through the support members.
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 design effectively reduces heat transfer, minimizes thermal stresses, and lowers manufacturing costs by using standard materials and eliminating the need for expensive tooling, while enhancing structural integrity and performance.
Implementation Method 1
the support members provide support for the fuel tube... radially interposed between the heat shield and the fuel tube
Implementation Method 2
the support/stem experiences significant thermal stresses due to thermal expansion and contraction... the plurality of support members are also positioned within, at least in part, the central cavity and support the fuel tube
Data Source
AI summary
A fuel nozzle is provided. The fuel nozzle includes a heat shield, a fuel tube and a plurality of support members. The support members are radially interposed between the heat shield and the fuel tube. The support members are preferably cylindrical tubes, thus creating voids or pockets between the heat shield and the fuel tube. The cylindrical tubes are connected to one another at a first end are free at an opposed end. As such, the tubes can move or slide relative to one another. Further, the tubes preferably only contact one another with at most line contacts. The fuel nozzle may also include a tip portion that includes a tip heat shield that extends radially outward from the primary heat shield. The tip heat shield defines a cavity that connects with the central cavity of the heat shield. The fuel tube extends through the tip heat shield.