Air Shroud Wipe Outlets for Carbon Deposition Prevention
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Solution Overview
Problem
Fuel nozzle air shrouds face issues with carbon deposition and thermal erosion due to exposure to hot combustion gases, leading to reduced performance and turbine erosion, and existing air-wipes often suffer from inadequate cooling and thermal expansion problems.
Innovation Solution
The air shroud design incorporates integral air wipe outlets that direct axial airflow tangentially or radially, with axially angled downstream surfaces and conical configurations, providing independent cooling and enhanced structural integrity to prevent carbon buildup and thermal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a smaller air-wipe is added outboard of the existing air-shroud to prevent carbon-formation or alleviate thermal-erosion, then carbon deposition and thermal erosion are reduced, but the air-wipe itself experiences thermal-erosion and requires additional cooling holes which may not provide sufficient cooling
Solution Approach 1:
The air-wipe is segmented into multiple sections with axial air outlets distributed along its length, allowing cooling air to be delivered to different zones of the air-wipe surface. This segmentation enables targeted thermal management at specific high-heat-exposure areas without requiring a single large cooling system.
Solution Approach 2:
Cooling air outlets are positioned on the axial (side) surfaces of the air-wipe rather than only on the downstream face, introducing cooling from a different spatial dimension. This axial cooling approach complements the traditional downstream face cooling by addressing thermal loads from multiple directions.
2Temperature
If additional cooling holes are added through the air-wipe to reduce thermal load, then thermal erosion is alleviated, but differential thermal expansion causes cracking and reduced life of the fuel nozzle
Solution Approach 1:
Axial air outlets are strategically positioned on the air-wipe at locations experiencing different thermal loads, providing localized cooling where most needed. This non-uniform cooling distribution addresses differential thermal expansion by cooling critical zones more aggressively, reducing thermal gradients and expansion differences across the air-wipe structure.
3Reliability
If the air-wipe is designed to direct compressor-discharge air downward over the face of the air-shroud, then carbon-formation is prevented, but insufficient compressor-discharge air is available in the vicinity of the air-wipe
Solution Approach 1:
Cooling air outlets are positioned on the axial surfaces of the air-wipe to deliver cooling air in advance to areas that will experience high thermal loads, rather than relying solely on air delivered from the downstream face. This preliminary cooling action reduces the demand for air from the limited compressor-discharge source.
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 design effectively reduces carbon deposition and thermal loading on air shroud components, extending their lifespan and improving structural integrity while maintaining airflow efficiency.
Implementation Method 1
directing compressor-discharge air downward over the face of the first (larger) air-shroud to either preferentially prevent carbon-formation or alleviate thermal-erosion
Implementation Method 2
a series of small holes through the air-wipe are added to provide additional cooler compressor-discharge air in order to reduce the thermal load
Implementation Method 3
The air wipe outlets can be angled to direct air in a generally radial direction toward a central axis of the air shroud. The air wipe outlets can be angled to direct air in a generally tangential direction relative to a central axis of the air shroud
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A
AI summary
An air shroud (100) for a nozzle includes an air shroud body (101) defining an inlet and an outlet (103) in fluid communication with one another to allow an outer airflow to issue therefrom. The air shroud (100) also includes an air wipe (107) disposed outboard of the air shroud body (101) including a web (109) defining a plurality of air wipe outlets (111) in fluid communication with a downstream surface (105) of the air shroud body (101) such that air can flow through the air wipe outlets (111) and wipe the downstream surface (105) of the air shroud body (101). The air wipe (107) can be integral with the air shroud body (101).