CMC Fuel Nozzle Swirler Heat Shield for Hot Gas Purging
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Solution Overview
Problem
Conventional gas turbine engines with metallic heat shields in TAPS fuel nozzle/swirler assemblies face deterioration due to high temperatures, requiring frequent and costly replacements, which is cumbersome and disrupts engine operation.
Innovation Solution
Implementing a ceramic matrix composite (CMC) heat shield in the TAPS fuel nozzle/swirler assembly, secured with a seal member and backplate, allowing for axial force retention and radial expansion, with purge orifices to prevent hot gas ingestion and facilitate easier maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallic heat shield is used in the TAPS fuel nozzle/swirler assembly, then the initial structural strength and heat resistance are sufficient, but the heat shield deteriorates over time due to high temperatures, requiring frequent and costly replacements
Solution Approach 1:
The patent applies composite materials by transitioning from a homogeneous metallic heat shield to a composite structure consisting of a CMC (ceramic matrix composite) heat shield combined with a metallic backplate and seal members. The CMC material provides superior high-temperature resistance and durability while the metallic components provide structural support and sealing, resolving the contradiction between initial strength and long-term durability under thermal stress.
2Ease of operation
If a metallic heat shield is used, then the assembly is structurally sound, but replacement is cumbersome and disrupts engine operation
Solution Approach 1:
The patent segments the heat shield assembly into separable components: the CMC heat shield, metallic backplate, seal members, and fasteners. This segmentation allows the heat shield to be independently replaced without replacing the entire assembly, significantly reducing maintenance time and engine downtime while maintaining structural integrity during operation.
Solution Approach 2:
The patent incorporates dynamic features including threaded fasteners that allow for easy assembly and disassembly, and a modular design that enables rapid replacement of the heat shield component. These dynamic characteristics facilitate quick maintenance operations, reducing the loss of time during engine maintenance while ensuring proper installation and sealing.
3Reliability
If the heat shield is secured tightly to prevent hot gas ingestion, then sealing effectiveness improves, but thermal expansion and contraction are restricted causing potential damage
Solution Approach 1:
The patent applies local quality by providing different sealing characteristics at different locations: the seal members provide flexible sealing at the interface between the heat shield and backplate to prevent hot gas ingestion, while the CMC material itself provides rigid thermal resistance. This localized differentiation of sealing properties maintains both sealing effectiveness and structural integrity under thermal cycling.
Solution Approach 2:
The patent utilizes parameter changes by selecting CMC material with specific thermal expansion properties that differ from metallic materials. The composite structure accommodates differential thermal expansion through the flexible seal members and designed clearances, allowing the heat shield to expand and contract freely during temperature cycles while maintaining effective sealing, thus preserving both reliability and strength.
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 CMC heat shield provides enhanced durability, reducing maintenance frequency and simplifying replacement, while maintaining engine performance.
Implementation Method 1
a downstream-facing surface of the heat shield is arranged radially between an outlet of the venturi and the fuel nozzle housing so as to provide protection of the fuel nozzle housing from flames and heat of combustion products
Implementation Method 2
a seal member is arranged between the backplate and the CMC heat shield to provide an axial force against the CMC heat shield so as to hold the CMC heat shield axially, while allowing radial and circumferential expansion
Implementation Method 3
a radial gap is provided between the CMC heat shield and the venturi, so as to allow a flow of purge air from the purge orifices to pass through the radial gap to purge any hot gases that may be ingested between the CMC heat shield, the venturi, and the backplate
Data Source
AI summary
A fuel nozzle/swirler assembly includes a venturi including a heat shield retaining wall. A backplate is connected to the venturi and includes a plurality of purge orifices extending through the backplate. A ceramic matrix composite (CMC) heat shield includes a heat shield attachment wall engaged between the heat shield retaining wall of the venturi and the backplate, and a seal member is arranged between the backplate and the CMC heat shield. The plurality of purge orifices are arranged between the seal member and the venturi and provide a flow of purge air therethrough to flow through a radial gap. The seal member provides a force against the CMC heat shield to axially engage the heat shield attachment wall of the CMC heat shield against the heat shield retaining wall of the venturi.