Mechanical Temperature Sensor for Solid Fuel Burner Air Inlet Control
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Solution Overview
Problem
Existing temperature sensing mechanisms for solid fuel burners, such as thermocouples, capillary thermostats, and bimetal strips, face issues like power requirements, material failure at high temperatures, and slow response times, making it difficult to effectively control air inlet valves for reducing PM2.5 emissions.
Innovation Solution
A mechanical temperature sensor using materials with different thermal expansion coefficients, such as Invar and cordierite, quartz, or stainless steel, to sense temperature changes and control air inlet valves through a lever mechanism, ensuring high force application and rapid response without material failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermocouple or thermistor is used to sense temperature, then temperature sensing capability is improved, but the device requires electrical power supply which complicates the simple low technology appliance
Solution Approach 1:
The patent replaces electrical sensing systems (thermocouple, thermistor) with a purely mechanical temperature sensing mechanism. The bimetallic strip mechanically responds to temperature changes through differential thermal expansion, directly actuating the valve without requiring electrical power supply, batteries, or electronic circuits.
Solution Approach 2:
The bimetallic strip system is self-actuating and self-regulating. It automatically senses temperature changes and mechanically closes the air inlet valve when the specified temperature is reached, without requiring external power sources, control electronics, or user intervention.
2Measurement precision
If a capillary thermostat is used to sense temperature, then temperature sensing capability is improved, but the fluid expands to such an extent at excessively high temperatures that the bulb, tube or diaphragm rupture
Solution Approach 1:
The patent utilizes differential thermal expansion of two metal strips with different coefficients of thermal expansion. The bimetallic strip bends in response to temperature changes, providing a reliable mechanical actuation mechanism that does not suffer from the rupture problem of capillary thermostats at excessively high temperatures.
Solution Approach 2:
The invention employs a composite structure consisting of two different metal strips bonded together to form a bimetallic strip. This composite material approach allows the system to withstand high temperatures reliably while providing the necessary temperature sensing and actuation functionality.
3Measurement precision
If a bimetal strip is used to sense temperature, then temperature sensing capability is improved, but the maximum temperature they can withstand is 550°C and the relationship between temperature and valve opening changes if the stove reaches excessively high temperature
Solution Approach 1:
The patent employs differential thermal expansion of the bimetallic strip to sense temperature changes and actuate the valve. By carefully selecting the two metal components with appropriate thermal expansion coefficients, the system achieves reliable operation across the required temperature range without the material deformation issues that limit conventional bimetal strips to 550°C.
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 provides a reliable and rapid mechanism to control air inlet valves, effectively reducing PM2.5 emissions by maintaining optimal flue gas temperatures, even at high stove temperatures, without requiring electrical power or additional components.
Implementation Method 1
a mechanical temperature sensor for sensing the temperature within the solid fuel burner, the sensor comprising first and second elongate parts having different coefficients of linear thermal expansion and arranged such that a first end of the first elongate part moves linearly in the elongate direction relative to a first end of the second elongate part in response to a change in the sensed temperature
Data Source
AI summary
Apparatus for controlling the flow of air through an air inlet in a solid fuel burner comprises: a mechanical temperature sensor for sensing the temperature within the solid fuel burner, the sensor comprising first and second elongate parts having different coefficients of linear thermal expansion and arranged such that a first end of the first elongate part moves linearly relative to a first end of the second elongate part in response to a change in the sensed temperature; a movable valve member for controlling the flow of air through the air inlet; and a mechanism for coupling the first end of the first elongate part to the movable valve member so as to close or restrict the air inlet as the sensed temperature increases.