Ventilated Spark Plug Guide for Gas Turbine Cooling
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Solution Overview
Problem
Existing spark plug cooling systems in gas turbine engines are inefficient due to variations in the expansion between the combustion chamber and its environment, leading to suboptimal heat transfer when the spark plug is not centrally located, affecting thermal resistance and re-ignition capabilities.
Innovation Solution
The cooling chamber is relocated to the level of the spark plug guide, ensuring that the cooling of the impact surface remains consistent despite variations in expansion, with an annular and coaxial cooling chamber surrounding the cylindrical wall portion of the spark plug guide, and radially oriented cooling air supply orifices that can be inclined to accommodate geometric constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cooling chamber is positioned at the original location, then the structure is simpler, but the cooling efficiency decreases when the spark plug is not centrally located due to variations in expansion
Solution Approach 1:
The cooling chamber is positioned at the level of the spark plug guide rather than fixed at the original location, allowing it to dynamically adapt to the spark plug's position variations caused by thermal expansion. This dynamic positioning ensures that the cooling air jets always impinge effectively on the spark plug surface regardless of its displacement, thereby maintaining reliable cooling efficiency while accommodating structural changes during operation.
2Reliability
If the spark plug is positioned closer to the fuel injection cone for better ignition, then the re-ignition capability improves, but the thermal resistance of the spark plug decreases
Solution Approach 1:
The cooling chamber acts as an intermediary cooling system positioned between the hot combustion environment and the spark plug. It introduces cooling air jets that directly impinge on the spark plug surface, creating a thermal barrier that protects the spark plug from excessive heat while allowing it to remain positioned for optimal ignition and re-ignition capability near the fuel injection cone.
3Temperature
If the spark plug is positioned farther from the fuel injection cone for better thermal resistance, then the thermal resistance improves, but the re-ignition capability decreases
Solution Approach 1:
The cooling chamber serves as a thermal management intermediary that enables the spark plug to be positioned optimally for re-ignition while providing active cooling protection. The cooling air jets introduced by the chamber create a protective thermal environment, allowing the spark plug to maintain both excellent thermal resistance and superior re-ignition capability regardless of its specific position relative to the fuel injection cone.
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 configuration maintains optimal cooling efficiency around the spark plug across various flight phases and thermal conditions, ensuring consistent thermal management and re-ignition capabilities.
Implementation Method 1
The air is introduced from outside the combustion chamber, due to the pressure difference, and maintains the temperature of the end of the spark plug exposed to the combustion gases and its radiation, at a level acceptable to the material that constitutes it.
Implementation Method 2
fine air jets form in the direction of the spark plug surface. The cooling produced by the jets depends on various parameters including the diameter of the orifices and the distance of the latter from the impact surface of the jets.
Implementation Method 3
The air is introduced from outside the combustion chamber, due to the pressure difference
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a combustion chamber of a gas turbine engine including a wall, a well (172) secured to the wall, the well forming a recess for a spark plug (13) leading into the combustion chamber, a spark-plug guide (175) mounted on the well such as to be transversally mobile relative to the axis of the well, the spark-plug guide (175) including a cylindrical wall portion (178) for guiding and supporting the spark plug and a seal ring (176) mounted such as to engage slidably with a bearing surface (173) of the well (172). According to the invention, the combustion chamber is characterised in that the spark-plug guide (175) is provided with a cooling chamber (174a) having openings (174c) for supplying cooling air to said chamber (174a).