Kanthal D Connection Element for Gas Burner Temperature Sensor
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Solution Overview
Problem
Existing temperature sensors for gas burners face issues with material compatibility, weldability, and reliability due to high temperatures and thermal gradients, leading to inaccurate readings and mechanical failures, particularly when using thermocouples with materials like Chromel and Alumel on stainless steel burners.
Innovation Solution
A temperature sensor assembly featuring a thermocouple with a connection element made from Kanthal® D alloy, which provides a secure and durable interface with the burner using an interference fit and laser welding, ensuring precise positioning and high thermal resistance, and is designed to withstand temperatures above 900°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electric conductors are directly welded to the burner surface, then the sensor can be securely attached, but material incompatibility forms hard and fragile intermetallic compounds that reduce welding uniformity and mechanical characteristics
Solution Approach 1:
The patent introduces a connection element as an intermediary component between the thermocouple conductors and the burner surface. This connection element is made of a material compatible with both the thermocouple conductors (Chromel and Alumel) and the burner material (stainless steel), preventing the formation of hard and fragile intermetallic compounds. The connection element facilitates secure attachment while maintaining welding uniformity and mechanical characteristics by mediating the material incompatibility between dissimilar materials.
2Measurement precision
If the sensor operates at high temperatures above 900°C, then accurate temperature measurement is achieved, but thermal gradients and thermal transients cause functional deterioration and cracks
Solution Approach 1:
The patent addresses thermal stress issues by carefully selecting the material composition and thermal properties of the connection element. The material is chosen to have appropriate thermal conductivity and expansion characteristics that reduce thermal gradients between the thermocouple and burner surface. This parameter optimization allows the sensor to operate at high temperatures above 900°C for accurate measurement while minimizing thermal transients that cause functional deterioration and cracks, thereby maintaining reliability.
3Ease of operation
If the thermocouple conductors are exposed to combustion products and water vapor, then temperature measurement function is maintained, but oxidation of metals accelerates causing functional deterioration
Solution Approach 1:
The connection element serves as a protective intermediary between the thermocouple conductors and the harsh combustion environment. It shields the sensitive metal conductors from direct exposure to oxidation-prone conditions including combustion products and water vapor. The connection element material is selected for its oxidation resistance, preventing metal oxidation while maintaining the temperature measurement function of the thermocouple.
4Measurement precision
If the thermocouple positioning is not precisely controlled, then assembly simplicity is maintained, but positioning accuracy limits repeatability and quality of the read signal
Solution Approach 1:
The connection element is designed with pre-formed geometric features such as recesses, protrusions, or keyed structures that guide and constrain the thermocouple conductors into precise positions during assembly. This preliminary design of the connection element ensures accurate positioning and high signal quality without requiring complex positioning mechanisms or procedures. The geometry itself performs the positioning function, maintaining assembly simplicity while achieving the required positioning accuracy for repeatable measurements.
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 the repeatability and accuracy of temperature readings, reduces material compatibility issues, and improves the durability of the sensor assembly, ensuring reliable operation and safety control of the burner within optimal pollution limits.
Implementation Method 1
a thermocouple (11) comprising two metallic conductors (15) spaced away from each other by a mineral oxide (16), everything enveloped by a protective element defined, in the example of the figures, by a known metallic protective sheath (17)
Implementation Method 2
laser welding
Data Source
AI summary
A temperature sensor (1) for gas burner (2) having a thermocouple (11) comprising electric conductors (15) and a connection element (12) to connect to the burner (2) associated with a free end (18) of such thermocouple (11), said connection element (12) being suitable for being inserted inside a seat of the sensor (8) formed inside a wall (4) of the burner (2) and having a first end (26) suitable for being placed at the outer surface (6) of the burner (2), said thermocouple (11) being inserted inside a blind hole (29) of the connection element (12) which opens at a second end (28) of said connection element (12). Said blind hole (29) ends with at least one part (31) convergent towards an end zone (K) of the hole (29), said part (31) getting in contact with the thermocouple (11) inserted inside the connection element, the connection element (12) being made from an iron-chrome-aluminum alloy. An assembly comprising such temperature sensor and a burner is also claimed.