Adjustable AC Voltage Pulses for Flame Ionization Sensitivity
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Solution Overview
Problem
Existing flame monitoring systems in heating devices require complex and costly circuitry to adjust the sensitivity of AC voltage for reliable and precise flame detection, which is not efficiently addressed by conventional AC voltage sources.
Innovation Solution
A method and device that generate individual AC voltage pulses with adjustable frequency and interval, allowing for simpler and cost-effective adjustment of effective amplitude, independent of the AC voltage shape, to set the sensitivity of flame monitoring, using an AC voltage source with frequencies greater than 1 kHz and adjustable pulse duty factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional AC voltage source with adjustable amplitude is used to adjust the sensitivity of flame monitoring, then the sensitivity can be adjusted, but the device complexity and cost increase due to requiring a relatively large transformer and considerable circuitry
Solution Approach 1:
The patent applies periodic action by using a train of AC voltage pulses instead of continuous AC voltage. The sensitivity adjustment is achieved by periodically applying voltage pulses with adjustable pulse width and spacing, rather than continuously adjusting the amplitude of a continuous voltage signal. This reduces the need for complex amplitude adjustment circuitry while maintaining the ability to control detector sensitivity.
Solution Approach 2:
The patent changes the parameters of the voltage signal from continuous amplitude adjustment to pulsed duration and spacing adjustment. By varying the pulse width (duty cycle) and the time spacing between pulses, the effective voltage applied to the detector can be controlled without requiring complex amplitude adjustment mechanisms, thereby simplifying the overall device complexity.
2Reliability
If an AC voltage source with high output resistance is used to generate ionization signal, then the voltage drops in one half-wave due to rectifier effect of flame, but adjusting the voltage amplitude requires considerable circuitry and equipment
Solution Approach 1:
The patent uses periodic AC voltage pulses to maintain reliable flame monitoring while simplifying the voltage adjustment mechanism. The pulsed nature of the voltage source, combined with the high output resistance, still produces the rectifier effect in the flame during each pulse, ensuring reliable detection without requiring complex continuous amplitude adjustment circuitry.
Solution Approach 2:
The patent introduces dynamic control through adjustable pulse width and spacing parameters. This allows the system to adapt to different operating conditions and maintain optimal sensitivity without requiring a large transformer or complex amplitude adjustment circuitry, thereby reducing device complexity while preserving monitoring reliability.
3Measurement precision
If continuous sinusoidal AC voltage is used for flame monitoring, then the ionization signal can be measured, but the equipment is more complex and costly compared to pulsed voltage approach
Solution Approach 1:
The patent replaces continuous sinusoidal AC voltage with periodic voltage pulses, significantly simplifying the equipment required for generation and control. The pulsed voltage source can be implemented with simpler electronics compared to a continuous variable amplitude AC source, reducing manufacturing cost and complexity while maintaining adequate measurement precision for flame monitoring.
Solution Approach 2:
The patent employs a simpler, less expensive pulsed voltage generation approach instead of expensive continuous adjustable AC voltage equipment. The pulsed voltage source requires less sophisticated components and can be manufactured at lower cost, achieving the same functional goal of ionization signal measurement without the need for expensive continuous sine wave generation equipment.
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
Enables reliable and precise flame monitoring with reduced equipment complexity and cost, maintaining consistent integral amplitudes and allowing for adaptive sensitivity adjustments during operation.
Implementation Method 1
the flame area ionized when flames are present having a rectifying effect, see above that an ionization current mainly only flows during a half cycle of the alternating current
Implementation Method 2
an AC voltage source generates individual AC voltage pulses of a definable AC voltage frequency and a definable length between an ionization electrode located in a flame area and a counter-electrode
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method and a device for adjusting the sensitivity of a detector (11) for monitoring a flame in a heating device (1), wherein an AC voltage source (12) generates individual AC voltage pulses (13) of an AC voltage frequency (F1) and a predefinable length (L) between an ionization electrode (7) located in a flame area (2) and a counter electrode (9), wherein there is a time interval (T) between the start of successive AC voltage pulses (13), and wherein the length (L) and/or the interval (T) of the individual AC voltage pulses (13) are adjustable. The device in a heating device (1) with an air supply (3) and a fuel gas supply (4) comprises an ionization electrode (7) in a flame area (2), a counter electrode (9), an AC voltage source (11), and evaluation electronics (14) for determining an ionization signal.The AC voltage source (12) is designed to generate individual AC voltage pulses (13) at time intervals (T) of an AC voltage frequency (F1), in particular greater than 1 kHz, and of a predefinable length (L), wherein the length (L) and/or the time interval (T) of the individual AC voltage pulses (13) are adjustable. By adjusting the effective amplitude of the AC voltage source (12) in this way, the sensitivity of the detector (11) can be adjusted.