Dual-Fuel Nozzle Assembly for Thermal Isolation and Backflow Prevention
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Solution Overview
Problem
Existing fuel nozzles in gas turbine engines, particularly in the aerospace industry, face challenges in efficiently managing thermal stress and preventing backflow of fuels, which can lead to coke deposition and self-ignition, affecting performance and safety.
Innovation Solution
A dual fuel nozzle assembly with a cylindrical air conduit positioned radially inward from the second fuel conduit, featuring an inner and outer heat shield, and a fuel swirler that isolates the first and second fuel conduits, along with an air cap forming an insulative air gap, to prevent backflow and thermal insulation, maintaining the first fuel conduit temperature below the coke formation threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dual fuel nozzle assembly is used to improve combustion efficiency, then fuel injection performance is improved, but thermal stress management and backflow prevention become more complex
Solution Approach 1:
The nozzle assembly is segmented into distinct functional zones: an inner heat shield protecting the first fuel conduit, an outer heat shield protecting the second fuel conduit, and separate air conduits for cooling. This segmentation allows independent thermal management of each fuel type, reducing overall system complexity despite the dual-fuel configuration.
Solution Approach 2:
The heat shields are nested concentrically around the fuel conduits, with the inner heat shield surrounding the first fuel conduit and the outer heat shield surrounding the second fuel conduit. This nested arrangement provides thermal protection while maintaining a compact structure, avoiding the need for separate external cooling systems.
2Reliability
If heat shields are added to protect fuel conduits from thermal stress, then fuel conduit protection is improved, but device complexity increases
Solution Approach 1:
The cooling function and thermal protection function are merged into a single integrated heat shield structure. The heat shields not only protect the fuel conduits from thermal stress but also incorporate air conduits that deliver cooling air directly to the fuel, combining protection and cooling in one component rather than requiring separate systems.
Solution Approach 2:
The heat shields serve multiple functions simultaneously: they act as thermal barriers protecting the fuel conduits from hot combustion gases, provide structural support for the nozzle assembly, and incorporate cooling air conduits for thermal management. This multi-functionality reduces the need for additional separate components.
3Reliability
If fuel conduits are fluidly isolated to prevent backflow and coke deposition, then fuel injection reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The air conduits are extracted as separate, distinct passages within the heat shield structure, rather than being integrated into the fuel conduits themselves. This separation allows the fuel conduits to be manufactured independently with simple fluid isolation, while the cooling function is provided by the separately-formed air conduits, reducing manufacturing complexity.
4Temperature
If an insulative air gap is created between heat shields to improve thermal insulation, then thermal management is improved, but device complexity increases
Solution Approach 1:
The insulative air gap acts as a thermal intermediary between the inner and outer heat shields. Rather than requiring direct thermal contact or complex thermal barrier materials, the air gap provides passive thermal insulation by exploiting the low thermal conductivity of stagnant air, simplifying the thermal management design.
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 solution enhances thermal management, prevents coke deposition, and ensures safe operation by isolating fuels, thereby improving nozzle performance and extending its operational life while ensuring safe combustion.
Implementation Method 1
thermally insulating the second fuel conduit from hot compressor air within the air conduit with the heat shield
Implementation Method 2
the outer heat shield further includes an air cap radially outward of the outer heat shield forming an insulative air gap therebetween
Implementation Method 3
The first fuel conduit is configured for issuing first fuel as a swirling, atomized spray into a combustor space
Implementation Method 4
The first fuel conduit is configured for issuing first fuel as a swirling, atomized spray into a combustor space
Data Source
Figure 1
Figure 2
AI summary
A nozzle assembly (100) comprises a first fuel conduit (102) defined between a nozzle body (104) and a fuel swirler (106) and extending along a longitudinal axis (A) from an inlet (114) of the first fuel conduit (102) to an outlet (116) of the fuel nozzle assembly (100). A second fuel conduit (118) is defined between the fuel swirler (106) and a heat shield (120) and extending along the fuel swirler (106) along the longitudinal axis (A) from an inlet (124) of the second fuel conduit (118) to the outlet (116) of the fuel nozzle assembly (100). An air conduit (126) extends through the heat shield (120) along the longitudinal axis (A) from an inlet (128) of the air conduit (126) to the outlet (116) of the fuel nozzle assembly (100).