Torch Igniter Cooling via Segmented Air Channels
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Solution Overview
Problem
Torch igniters in gas turbine engines face durability issues due to high temperatures exceeding 1650-2200°C, which exceed the thermal limits of conventional materials used in their construction, leading to potential thermal stress and reduced longevity.
Innovation Solution
A cooling arrangement using high-pressure air from the gas turbine engine to cool the torch igniter, which is then utilized for combustion, preventing thermal stress and allowing the igniter to be constructed from high-temperature metallic components, including those produced via additive manufacturing with complex cooling structures like fins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional materials are used in torch igniter construction, then manufacturing cost and ease of manufacture are improved, but thermal durability and reliability deteriorate due to temperatures exceeding 1650-2200°C
Solution Approach 1:
The torch igniter is divided into multiple sections with independent cooling channels. Each section can be manufactured separately and then assembled, allowing the use of advanced materials in critical high-temperature zones while maintaining manufacturing feasibility. The segmentation enables complex internal cooling structures to be created without requiring monolithic manufacturing of the entire component.
Solution Approach 2:
The patent employs composite material construction where refractory ceramic materials are used in direct contact with combustion gases to withstand extreme temperatures, while metallic materials are used in structural components requiring mechanical strength and toughness. This composite approach allows each material to be used in its optimal performance range, achieving both thermal durability and manufacturability.
2Temperature
If advanced cooling structures like fins are added to the torch igniter, then thermal management and durability are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The cooling system utilizes high-pressure air flow from the gas turbine engine's compressor section. Complex internal cooling channels and fin structures are designed to efficiently distribute this pressurized air flow, using fluid dynamics principles to maximize cooling effectiveness. The pneumatic cooling approach allows sophisticated thermal management without requiring additional mechanical cooling components.
Solution Approach 2:
Cooling fins and channels are strategically positioned in specific high-heat zones of the torch igniter rather than uniformly distributed throughout. The density and configuration of cooling structures vary locally based on thermal load analysis, providing enhanced cooling where needed most while minimizing overall device complexity and material usage.
3Productivity
If the torch igniter is designed for continuous operation at high temperatures, then productivity and operational efficiency are improved, but thermal stress and material degradation accelerate
Solution Approach 1:
The cooling channels are pre-designed and pre-cooled using ambient air from the compressor section before the torch igniter is exposed to combustion temperatures. This preliminary cooling action establishes a thermal buffer that delays the onset of thermal stress on materials, extending the component's service life during continuous high-temperature operation.
Solution Approach 2:
The cooling system operates continuously throughout the torch igniter's operational life, with cooling air flowing constantly through the internal channels. This continuous cooling action maintains a stable thermal gradient across the igniter walls, preventing thermal cycling fatigue and enabling uninterrupted operation at high temperatures without accumulating thermal damage.
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 cooling system enhances the durability of the torch igniter by maintaining operational efficiency and reducing fuel consumption, enabling continuous operation and minimizing the risk of thermal damage, while allowing for the use of metallic materials that can withstand the extreme temperatures.
Implementation Method 1
a cooling channel forming a flow path between the igniter wall and the structural wall... configured to direct the flow of air to flow across an exterior surface of the igniter tip and toward a base of the igniter
Implementation Method 2
The flow path has a first axial section, a second axial section, a radially inward section, and a radially outward section... configured to direct the flow of air axially from the air inlet toward the tip
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An embodiment of a torch igniter (10) for a combustor of a gas turbine engine includes a combustion chamber (16) oriented about an axis, a cap (34) defining the axially upstream end of the combustion chamber and situated on the axis, a tip (30) defining the axially downstream end of the combustion chamber (16), an igniter wall (38) extending from the cap to the tip and defining a radial extent of the combustion chamber, a structural wall (36) coaxial with and surrounding the igniter wall, an outlet passage (40) defined by the igniter wall within the tip, wherein the outlet passage fluidly connects the combustion chamber to the combustor of the gas turbine engine, and a cooling system. The cooling system has an air inlet, a cooling channel (28), and an aperture. The cooling channel (28) forms a flow path having a first axial section, a second axial section, a radially inward section, and a radially outward section.