Heating Device Combustion Control via Ionization Signal Calibration
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Solution Overview
Problem
Existing combustion control systems in heating devices face challenges with electrode drift, leading to inaccurate lambda value measurements, increased carbon monoxide production, and reduced electrode lifespan, necessitating frequent recalibration that can disrupt stable operation and produce unwanted emissions.
Innovation Solution
A method that adjusts the blower speed and fuel gas valve position based on ionization signal measurements to maintain a stable lambda value, using a calibration point close to the desired operating point, reducing carbon monoxide production and extending electrode lifespan, with an emergency control system switching to secondary ionization measurement in case of primary system failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed by operating at lambda=1 to compensate for electrode drift, then measurement precision is improved, but carbon monoxide production increases and electrode lifespan decreases
Solution Approach 1:
The patent changes the calibration parameter from lambda=1 to lambda=1.3, operating at a richer air-fuel ratio that avoids carbon monoxide production while still providing accurate calibration data for compensating electrode drift
Solution Approach 2:
The patent converts the normally harmful effect of rich mixture (lambda>1) into a beneficial calibration condition, using the richer air-fuel ratio to protect the electrode and avoid carbon monoxide while achieving calibration goals
2Measurement precision
If calibration is performed by operating at lambda=1 to compensate for electrode drift, then measurement precision is improved, but electrode lifespan decreases
Solution Approach 1:
The patent changes the calibration operating point from lambda=1 to lambda=1.3, which reduces flame temperature and prevents excessive thermal stress on the electrode, thereby extending its service life while maintaining calibration accuracy
Solution Approach 2:
The patent converts the potentially harmful high-temperature stoichiometric combustion into a beneficial cooler combustion process at lambda=1.3, protecting the electrode from thermal damage while achieving calibration objectives
3Measurement precision
If recalibration is performed frequently to compensate for electrode drift, then measurement precision is maintained, but stable operation is disrupted and carbon monoxide is produced
Solution Approach 1:
The patent changes the calibration approach by using a richer mixture (lambda=1.3) that allows for gradual, stable calibration without disrupting normal combustion operation, enabling frequent recalibration without compromising stability
Solution Approach 2:
The patent converts the disruption caused by frequent recalibration at lambda=1 into a benefit by performing calibration at lambda=1.3, which maintains combustion stability and avoids carbon monoxide production even during repeated calibration cycles
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 allows for reliable, long-term stable control of combustion with minimal carbon monoxide production, maintaining optimal lambda values and extending the service life of ionization electrodes, while enabling seamless switchover to emergency operation without shutting down the heater.
Implementation Method 1
an ionization measurement is carried out in a flame area... an ionization current mainly flows only during a half-wave of the alternating current... the respective actual value of the ionization in the flame area is determined, which is proportional to the current lambda value
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for controlling combustion in a heating appliance (1) by means of an ionization signal measured in a flame area (2) of the heating appliance (1), which is operated with combustion air and fuel gas. This signal is derived from an ion current flowing through the flame area (2) from an ionization electrode (8) to a counter electrode (9). The lambda value during combustion in the heating appliance (1) is determined from the ionization signal using calibration data and is controlled by adjusting the supply of fuel gas and/or the supply of combustion air, comprising the following steps: a blower (5) for supplying combustion air is brought to a predefinable speed; a fuel gas valve (6) is brought to a position corresponding to this speed by means of a predefinable characteristic curve; the fuel gas valve (6) is held in this position; the speed is reduced by a predefinable amount.The fan speed is then increased and the respective ionization signal (I2) is measured. A minimum of the ionization signal (I2) is detected and stored. The fan speed is further increased until a predefined threshold value of the ionization signal (I2) relative to the minimum is reached. The fan speed is then reduced to the speed corresponding to the minimum and held there for a period (t) or used to regulate the ionization signal (I2) to its current constant value. After the period (t) has elapsed, the steps from 1.4 are repeated. This method can be used as a primary control system or as an emergency control system in case of failure of another primary control system.