Turbine Fuel Injection System Film Cooling
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Solution Overview
Problem
Turbine engine combustor components face increased risk of auto-ignition and reduced operational lifetime due to inadequate cooling, leading to potential flashback and shortened maintenance intervals, especially with fuel nozzle systems that increase NOx emissions.
Innovation Solution
A fuel injection system with an annular fuel injection housing and separate air manifolds forming air cushions between the fuel stream and the housing surface, reducing the risk of auto-ignition and enhancing fuel-air mixing to minimize NOx production, utilizing a swirler for efficient air-fuel mixing and film cooling with only 0.5% to 3% of the compressor air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If fuel nozzle assemblies are used to pre-mix fuel and air for lean combustion, then NOx emissions are reduced, but the potential for auto-ignition or flashback of residual fuel increases due to inadequate cooling of the system structure
Solution Approach 1:
Cooling air is introduced upstream of the fuel injection ports to pre-cool the fuel stream before it contacts the housing surface. This preliminary cooling action prevents residual fuel from auto-igniting or flashing back while maintaining the lean combustion configuration that reduces NOx emissions
Solution Approach 2:
A stream of cooling air acts as an intermediary substance between the hot housing surface and the fuel stream. This intermediary cooling air layer absorbs heat and prevents direct thermal contact that would cause auto-ignition, while allowing the fuel-air pre-mixing configuration to continue operating for NOx reduction
2Reliability
If adequate cooling is provided to prevent auto-ignition, then reliability improves, but the system complexity and structural requirements increase
Solution Approach 1:
The cooling air manifold serves multiple functions: it cools the fuel stream before injection, cools the housing surface, and helps establish proper fuel-air mixing. This multi-functionality reduces the need for separate dedicated cooling components, thereby limiting the increase in system complexity while maintaining reliability
Solution Approach 2:
The system uses a small portion (0.5% to 3%) of the existing compressor air output to provide self-cooling. The cooling air is drawn from the natural airflow through the combustor, eliminating the need for separate cooling fans or external cooling systems, thus maintaining simplicity while improving reliability
3Duration of action of stationary object
If film cooling is implemented with air cushions, then operational lifetime is extended, but the use of compressor air increases
Solution Approach 1:
Only a small partial amount of compressor air (0.5% to 3% of total output) is diverted for cooling purposes. This partial action provides sufficient film cooling protection to extend operational lifetime while minimizing the impact on overall air availability for combustion
Solution Approach 2:
The system changes the parameter of air flow distribution by diverting a small controlled portion of compressor air to the cooling manifold. This parameter change optimizes the balance between cooling effectiveness for extended lifetime and air consumption, ensuring sufficient air remains for the combustion process
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 system reduces NOx emissions, extends combustor component life, maintains flame stability, and improves turbine engine efficiency by minimizing auto-ignition risks and optimizing fuel-air mixing, thereby reducing maintenance needs and enhancing operational conditions.
Implementation Method 1
Each air injection port of the first plurality of air injection ports and second plurality of air injection ports is configured to introduce an air cushion into the annular cavity to facilitate film cooling of the fuel injection housing
Implementation Method 2
The fuel manifold includes a plurality of fuel injection ports extending through the fuel injection housing. Each fuel injection port of the plurality of fuel injection ports is configured to introduce a fuel stream into the annular cavity
Implementation Method 3
The fuel injection system is in fluid communication with the annular cavity defined between the main housing and the fuel injection housing
Data Source
AI summary
A fuel injection system for use in a combustor of a turbine assembly includes a substantially annular fuel injection housing at least partially defining an annular cavity. The fuel injection system also includes a fuel manifold and an air manifold. The fuel manifold includes a plurality of fuel injection ports extending through the fuel injection housing. The air manifold includes a first plurality of air injection ports and a second plurality of air injection ports that each extends through the fuel injection housing.