Flame Rod with LSM Coating for Thermal Stress Relief
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Solution Overview
Problem
Conventional flame rods in combustion devices face issues with conductivity and heat resistance due to alumina deposition, and ceramic cover layers suffer from cracking and peeling-off caused by thermal expansion differences, leading to productivity and detection failure problems.
Innovation Solution
A flame rod with a metal rod portion coated by a protective lanthanum-strontium-manganese oxide (LSM) cover layer of specific thickness (0.002 mm to 0.1 mm) that enhances conductivity and heat resistance, and includes a thin alumina layer for corrosion protection, allowing easy adjustment and maintaining stability during thermal cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thermal expansion coefficient of the ceramic cover layer is made to approximate the thermal expansion coefficient of the rod portion, then cracking and peeling-off are reduced, but manufacturing precision requirements increase and productivity decreases
Solution Approach 1:
The patent changes the material composition parameters of the ceramic cover layer by incorporating alumina (Al2O3) in controlled amounts (0-60 wt%) alongside the conductive ceramic material. This compositional parameter adjustment allows the thermal expansion coefficient to be tuned to match the metal rod portion, reducing thermal stress and preventing cracking/peeling without requiring high-precision thickness control
Solution Approach 2:
The patent creates a composite ceramic cover layer by combining conductive ceramic materials (such as LSM - lanthanum strontium manganese oxide) with alumina. This composite structure achieves both high conductivity and matched thermal expansion characteristics, resolving the contradiction between reliability and manufacturing simplicity
2Reliability
If the thickness of the ceramic cover layer is set to 0.1 mm or more to secure conductivity, then conductivity is improved, but manufacturing complexity increases and heat transfer efficiency decreases
Solution Approach 1:
The patent changes the material properties of the ceramic cover layer by using highly conductive ceramic materials (such as LSM with conductivity of 10^-3 to 10^-6 S/cm) and optimizing composition ratios. This allows the layer to achieve sufficient conductivity at much thinner thicknesses (0.002 to 0.1 mm), eliminating the need for complex manufacturing processes required for thicker layers
3Reliability
If an intermediate coating layer is formed between the rod portion and the ceramic cover layer, then cracking and peeling-off are reduced, but manufacturing time and process complexity increase
Solution Approach 1:
The patent merges the intermediate coating layer function into the ceramic cover layer itself by incorporating alumina particles or forming an alumina-containing phase within the ceramic cover layer matrix. This integration eliminates the need for a separate intermediate coating layer while maintaining the bonding stability and thermal expansion matching benefits, thereby reducing manufacturing steps and cycle time
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 ensures stable conductivity and heat resistance, prevents cracking and peeling of the cover layer, and simplifies manufacturing by eliminating the need for precise thickness control, thereby enhancing productivity and reducing detection failures over extended use periods.
Implementation Method 1
a protective cover layer containing a cover material having high conductivity and high heat resistance... a flame current flowing through the flame is transmitted through the ceramic cover layer
Implementation Method 2
low electrically conductive alumina is deposited on a surface of the rod portion by an oxidation reaction of the aluminum
Implementation Method 3
a flame current flowing through the flame is transmitted through the ceramic cover layer to an non-insertion portion that is disposed outside the flame
Data Source
AI summary
A flame rod (1) including: a rod portion (11) made of a metal material containing aluminum; and a protective cover layer (21) containing a cover material having high conductivity and high heat resistance, wherein the protective cover layer (21) covers a surface of an insertion portion (11A) of the flame rod (11), and the protective cover layer (11) has a thickness of 0.002 mm or more and less than 0.1 mm.