Staged Fuel Injector Cooling via Pilot Flow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Staged fuel injectors for gas turbine engines face challenges in preventing carbon formation or coking in the main fuel circuit during low power operation, as existing cooling designs are inadequate for higher engine power levels, leading to overheating and degraded engine performance.
Innovation Solution
The design incorporates a staged fuel injector with a main fuel circuit and a pilot fuel circuit, utilizing radial passages and additive manufacturing techniques to form cooling channels near the spin chamber, allowing the pilot fuel flow to effectively cool the main fuel circuit exit ports, thereby preventing coking and enhancing engine performance at higher power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single cooling channel is used to cool the main atomizer exit slots, then cooling is effective at lower compressor discharge temperatures (up to 30% maximum take-off thrust), but the cooling becomes inadequate at higher power levels (up to 60% maximum take-off thrust) where compressor discharge temperature increases substantially
Solution Approach 1:
The single cooling channel is divided into multiple cooling channels (first cooling channel and second cooling channel) that are positioned at different locations to cool different regions of the main fuel circuit. This segmentation allows each channel to target specific hot spots, providing comprehensive cooling coverage across the entire fuel circuit structure.
Solution Approach 2:
Different cooling channels are positioned to cool specific local regions of the main fuel circuit based on their thermal characteristics. The first cooling channel cools the outer surface while the second cooling channel cools the inner surface, ensuring that each region receives appropriate cooling based on its local thermal requirements.
2Reliability
If passive insulation or heat shields are used to protect the main fuel circuit from carbon formation, then protection is provided without active cooling, but the solution is insufficient for higher engine power levels where temperatures exceed passive protection capabilities
Solution Approach 1:
The pilot fuel circuit serves dual purposes: it delivers fuel to the pilot atomizer for combustion control and simultaneously acts as a cooling mechanism for the main fuel circuit. The pilot fuel flow through the cooling channels absorbs heat from the main fuel circuit, preventing carbon formation without requiring separate active cooling systems.
Solution Approach 2:
The pilot fuel circuit is designed to perform multiple functions: fuel delivery to the pilot atomizer, cooling of the main fuel circuit through integrated cooling channels, and prevention of carbon formation. This multi-functionality eliminates the need for separate cooling systems and maximizes the utility of the pilot fuel flow.
3Ease of operation
If the pilot fuel circuit is operated alone during low power operation, then engine control is achieved, but stagnant fuel in the main fuel circuit becomes susceptible to carbon formation or coking due to operating temperatures
Solution Approach 1:
The pilot fuel flow is maintained continuously through the cooling channels during low power operation, ensuring continuous cooling of the main fuel circuit. This continuous flow prevents stagnant fuel from overheating and forming carbon deposits, maintaining the cooling action throughout the operational cycle.
Solution Approach 2:
The pilot fuel flow acts as an intermediary cooling medium that transfers heat away from the main fuel circuit during low power operation. By introducing this intermediate cooling flow, the system prevents direct thermal interaction between the hot main fuel circuit and the surrounding environment that would cause carbon formation.
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 solution reduces maximum temperatures near the main exit slots, enabling engine staging at higher power levels and extending injector life by using the pilot fuel flow as a multi-pass heat exchanger to cool the main fuel circuit, resulting in improved engine performance and reduced carbon formation.
Implementation Method 1
portions of the pilot fuel circuit are formed in the prefilmer and the fuel swirler and are positioned proximate to and in thermal contact with fuel exit ports associated with the main fuel circuit
Implementation Method 2
using the pilot fuel flow as a multi-pass heat exchanger to cool the main fuel circuit
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention is directed to a staged fuel injector that includes, inter alia, a main fuel circuit for delivering fuel to a main fuel atomizer and a pilot fuel circuit for delivering fuel to a pilot fuel atomizer which is located radially inward of the main fuel atomizer. The main fuel atomizer includes a radially outer prefilmer and a radially inner fuel swirler. Portions of the main fuel circuit are formed in the prefilmer and portions of the pilot fuel circuit are formed in the prefilmer and the fuel swirler and are positioned proximate to and in thermal contact with fuel exit ports associated with the main fuel circuit and formed in the prefilmer. As a result, the pilot fuel circuit cools the stagnant fuel located in main fuel circuit, including the exit ports, even when performing at engine power levels of up to 60% of the maximum take-off thrust.