Gas Turbine Spark Plug Internal Cooling via Pressure Gradient
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Solution Overview
Problem
Spark plugs in gas turbine engines face reduced lifetime due to exposure to high pressures, fluids, and temperatures, leading to increased maintenance costs and reduced aircraft reliability, with existing cooling methods being insufficient, especially for the exterior and nose of the spark plug.
Innovation Solution
A spark plug design that utilizes internal air circulation through clearances between components and pressure differentials to create cooling, with air inlets and outlets strategically positioned to circulate cooling air internally and evacuate heated air, enhancing cooling efficiency at the hottest end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external bypass cooling is used, then the exterior of the spark plug is cooled, but the internal components (electrodes and insulator) remain insufficiently cooled
Solution Approach 1:
The cooling system is segmented into multiple independent cooling paths: external bypass cooling for the outer body, and internal cooling through clearances for the electrodes and insulator. This segmentation allows each component to be cooled appropriately, with the internal clearance cooling specifically targeting the hottest zones that external cooling cannot reach.
Solution Approach 2:
The internal cooling mechanism is nested within the spark plug structure itself, utilizing the existing clearances between components. The cooling air inlet is positioned within the external body, and the cooling air flows through the internal clearances nested between the electrode and insulator, creating a nested cooling system that reaches the core hot zones.
2Temperature
If cooling air circulation is implemented, then temperature resistance is improved, but device complexity increases
Solution Approach 1:
The cooling system utilizes the existing pressure differential between the bypass and flame tube to drive cooling air circulation automatically, without requiring external pumps or complex control systems. The system serves itself by using the natural pressure gradient created during engine operation to circulate cooling air through the internal clearances.
Solution Approach 2:
The clearances between existing components (electrode and insulator) serve dual functions: maintaining electrical insulation and providing cooling air passage. The external body serves both as a structural component and as a housing for the cooling air inlet. This multi-functionality reduces the need for additional dedicated cooling components.
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 design significantly extends the spark plug's lifetime by effectively cooling critical zones, improving temperature resistance and reducing maintenance costs through enhanced internal cooling mechanisms.
Implementation Method 1
the structure enables an internal cooling by circulation of air inside internal spaces defined by said clearances
Implementation Method 2
cools a spark plug 24 by impact of air passing via the spark plug guide 25 and by conduction over the upper portion of the spark plug 24
Implementation Method 3
It also profits from the pressure differential that exists between the bypass and the flame tube to create a cooling at the hottest end of the spark plug opposite the flame and to make cooling air circulate inside the spark plug
Data Source
AI summary
A spark plug for combustion chamber of a gas turbine engine including: an external body forming ground electrode, intended to be received mainly in a bypass of the combustion chamber; an internal central electrode; and an interposed insulator with clearance between the external body and the internal electrode, is provided. The spark plug terminates in a nose forming portion to be received in the flame tube of the chamber of the combustion chamber, and a semi-conductor element being interposed between the central electrode and the ground electrode at the level of said nose forming portion. The external body includes at least one cooling air inlet which communicates inside the spark plug with at least one outlet arranged at the level of the nose forming portion.