Turbomachine Sparkplug Radial Positioning via Threaded Guide
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Solution Overview
Problem
The service life of sparkplugs in gas turbine engines is limited by high voltage breakdown, exposure to fuel or water, and high temperatures, leading to inconsistent radial positioning and reduced ignition efficiency.
Innovation Solution
A turbomachine sparkplug assembly with a radially secured sparkplug and guide, featuring screw threads for stabilization, axial sliding means to reduce friction, and a seal system with deformable seals and air passages for cooling, along with centering systems to maintain constant radial position and reduce vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sparkplug is secured using a conventional adapter fixed to the outer casing, then the sparkplug can be installed and removed, but the radial positioning becomes inconsistent due to thermal expansion and contraction of the combustion chamber
Solution Approach 1:
The sparkplug guide is designed to move radially with the combustion chamber during thermal expansion and contraction, while the sparkplug itself remains stationary relative to the guide through threaded engagement. This dynamic adjustment maintains consistent radial positioning of the sparkplug tip throughout the service life, resolving the contradiction between positioning consistency and service life duration
Solution Approach 2:
The sparkplug guide acts as an intermediary between the fixed adapter and the sparkplug. It absorbs the thermal movement of the combustion chamber through radial sliding on the external shell, while maintaining a stable threaded connection with the sparkplug, thereby ensuring consistent radial positioning throughout operation
2Reliability
If the sparkplug guide is fixed permanently to the outer casing, then radial positioning is stable, but friction prevents axial sliding during thermal dilation phases
Solution Approach 1:
The sparkplug guide has different local properties: the radial surface in contact with the external shell has low friction characteristics enabling sliding, while the threaded portion maintains strong engagement with the sparkplug. This local differentiation allows simultaneous radial stability and axial mobility during thermal cycles
3Temperature
If the sparkplug nose emerges from the external shell during operation, then thermal expansion occurs naturally, but the sparkplug enters the flame zone causing high temperature exposure and reduced service life
Solution Approach 1:
The sparkplug guide serves as a mediator that allows the combustion chamber to expand thermally while preventing the sparkplug nose from emerging into the flame zone. The guide's radial movement compensates for chamber expansion, maintaining the sparkplug tip position flush with the external shell and protecting it from excessive thermal exposure
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 solution enhances sparkplug durability, maintains consistent radial positioning, improves ignition capability, and extends service life by reducing thermal stress and vibrations while ensuring gas-tightness and efficient cooling.
Implementation Method 1
the sparkplug and the sparkplug guide each have a screw thread, the screw threads being screwed together so as to stabilise the sparkplug radially to the axis of the combustion chamber
Implementation Method 2
axial sliding means to reduce friction
Implementation Method 3
at least one seal arranged in abutment between an inner edge of the sparkplug adapter and the collar
Implementation Method 4
air passages for cooling
Implementation Method 5
centering systems to maintain constant radial position and reduce vibrations
Data Source
AI summary
Assembly comprising, on a turbomachine:—a combustion chamber (30) having a longitudinal axis (30a) and comprising: internal and external longitudinal walls (90) having a first opening (90a) substantially transverse to said axis (30a), an outer casing (110) having a second opening (110a) likewise substantially transverse to said axis (30a),—a turbomachine sparkplug (150),—a device (130) for radially securing the sparkplug (150), which device (130) comprises a sparkplug adapter (160) fixed toward a first end to the outer casing (110), facing the second opening (110a) and through which adapter and casing the sparkplug (150) in question passes, and a sparkplug guide (190) kept in contact with the external longitudinal wall (90), facing the first opening (90a) and through which the sparkplug (150) passes to emerge in the combustion chamber (30), the sparkplug (150) and the sparkplug guide (190) each having a screw thread (103, 105), the screw threads (103, 105) being screwed together so as to stabilize the sparkplug (150) radially to the axis (30a) of the combustion chamber (30) with respect to said external longitudinal wall (90), and—in this condition, the sparkplug (150) and the sparkplug guide (190) are mounted freely with respect to the outer casing (110) in a direction substantially radial to the axis of the second opening (110a).