Spark Plug Guide Elastic Biasing for Turbine Wear
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Solution Overview
Problem
In turbomachines, the high contact pressure and vibrations between the guide and spark plug in annular combustion chambers lead to premature wear of the spark plug due to differential expansions and air flow, causing functional issues.
Innovation Solution
Incorporating an elastic member, such as a spring or elastic washer, to bias the annular collar of the guide within the chimney's annular groove, allowing for axial and transverse clearance to compensate for expansions while limiting vibrations and wear by frictional damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the guide is mounted with clearance on the chimney to allow differential expansion movements, then the reliability of the combustion chamber is improved, but the guide rotates around the spark plug due to vibrations and air flow, causing premature wear
Solution Approach 1:
The guide is designed with both clearance for movement and elastic biasing elements. The elastic member allows the guide to dynamically adjust its position to accommodate thermal expansion while maintaining sufficient contact pressure to prevent rotation and wear during operation.
Solution Approach 2:
The elastic member changes the contact pressure parameter dynamically. During cold conditions, clearance exists allowing expansion movements. During hot operation, the elastic member biases the guide to maintain optimal contact pressure, preventing rotation and wear while still allowing for thermal movements.
2Ease of operation
If the contact zone dimensions are reduced to minimize interference, then the ease of operation is improved, but the contact pressure or Hertz pressure becomes high, leading to increased wear
Solution Approach 1:
The elastic member dynamically adjusts the contact pressure parameter. While the contact zone dimensions remain small for ease of assembly, the elastic biasing compensates by maintaining optimal contact pressure, preventing both excessive wear and rotation during operation.
3Adaptability or versatility
If the guide is allowed to move in translation relative to the spark plug, then the adaptability to thermal expansions is improved, but the vibrations and air flow cause the guide to rotate around the spark plug
Solution Approach 1:
The guide system is designed with dynamic characteristics - clearance allows translational movement for thermal adaptation, while elastic biasing provides rotational stability by maintaining contact pressure that prevents vibration-induced rotation.
Solution Approach 2:
The elastic member acts as an intermediary between the guide and chimney. It mediates between the need for movement (thermal adaptation) and the need for stability (preventing rotation), allowing translation while constraining rotation through biased contact.
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 elastic member effectively reduces spark plug wear by damping vibrations and enabling necessary movements to accommodate thermal expansions, ensuring reliable operation.
Implementation Method 1
limit the wear of the spark plug by frictional damping
Implementation Method 2
compensate for the expansions during the various phases of flight
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The infunnelion relates to the combustion chamber of a turbine engine, comprising at least one spark plug (11) borne by an outer casing and extending inside guiding means (14) borne by a rotating wall (3) of the chamber, said guiding means (14) including a tubular guide (16) traversed axially by the spark plug (11) and mounted with axial (j1) and transverse (j2) clearance on a funnel (15) secured to, and opening at, the rotating wall (3) of the chamber. In addition, the guide (16) comprises a flange ring (19) inserted with clearance (j1, j2) into an inner annular groove (20) in the funnel (15). The flange ring (19) is urged against a wall (24) of the groove (20) by an elastic member (25) mounted in the groove (20).