Burner-Heat Exchanger Electrodes for Stable Flame Current Sensing
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Solution Overview
Problem
Conventional flame current measurement methods in water heating devices are sensitive to variations in electrode distance, soot deposition, and temperature fluctuations, making them less reliable for determining the excess air factor and ensuring safe combustion.
Innovation Solution
The use of a water heating device with a burner and heat exchanger as electrodes, eliminating the need for a separate measuring pin, reduces sensitivity to electrode placement and temperature, and increases the surface area for a more stable and sensitive flame current measurement, allowing for better detection of combustion completeness and excess air factor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate measuring pin is used for flame current measurement, then the measurement can be performed, but the measurement is sensitive to variations in electrode distance and soot deposition
Solution Approach 1:
The patent merges the burner and heat exchanger, which are existing components in the water heating device, to form the two electrodes for flame current measurement. This eliminates the need for a separate measuring pin and utilizes the inherent structural components for measurement purposes, thereby reducing sensitivity to electrode placement variations and soot deposition.
Solution Approach 2:
The burner and heat exchanger serve dual functions: they perform their primary thermal functions (combustion and heat exchange) while simultaneously serving as electrodes for flame current measurement. This multi-functionality reduces the number of separate components needed and improves measurement reliability by using robust, existing structural elements.
2Measurement precision
If a small electrode (measuring pin) is used, then the device complexity is reduced, but the measurement sensitivity and resolution are insufficient
Solution Approach 1:
The patent combines the functional roles of the burner, heat exchanger, and measurement electrodes into a single integrated configuration. The burner and heat exchanger are used as electrodes, eliminating the need for separate small measuring pins while providing larger surface areas that enhance measurement sensitivity and resolution.
3Measurement precision
If the heat exchanger is electrically connected to the burner, then the structure is simpler, but the flame current measurement cannot be performed
Solution Approach 1:
The patent extracts the electrical connection requirement from the thermal connection between the burner and heat exchanger. While these components remain thermally connected for heat exchange, they are electrically isolated to function as separate electrodes. This is achieved through electrical insulation at specific points, allowing flame current measurement while maintaining thermal efficiency.
4Reliability
If excess oxygen is increased to ensure complete combustion, then safety is improved, but combustion efficiency decreases due to unnecessary heating of excess air
Solution Approach 1:
The patent implements feedback control by measuring the flame current between the burner and heat exchanger. The measured flame current provides information about combustion completeness, allowing the control system to adjust the air-fuel ratio to maintain optimal combustion conditions. This ensures complete combustion (safety) while minimizing excess air (energy efficiency).
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
This approach results in a more reliable flame current measurement with higher sensitivity and resolution, enabling precise control of the air/fuel ratio and enhanced safety against incomplete combustion, with a greater flame current and reduced interference from deposits and temperature fluctuations.
Implementation Method 1
Use is made of the fact that the heat of a flame ionizes gas molecules, for instance in the air
Implementation Method 2
A small current hereby flows between electrode 12 and heat exchanger 40
Data Source
Figure 1~2
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Figure 4
AI summary
The invention relates to a water heating device, comprising a burner (20) and a flame current measuring device (100) for measuring a flame current, which measuring device comprises two electrodes and a voltage source (14), wherein each of the poles (18, 19) of the voltage source is connected to one of the electrodes. The water heating device further comprises a heat exchanger (40) which is electrically insulated relative to the burner. The burner and the heat exchanger here form the electrodes of the flame current measuring device. The heat exchanger functioning as electrode can be earthed (41). The measured flame current can be used to determine the excess air factor of the combustion. The water heating device can further comprise an air/fuel controller for controlling the air/fuel ratio, wherein the air/ fuel controller uses the determined excess air factor to control the air/ fuel ratio. The invention also relates to a method for measuring a flame current in a flame.