Burner System AC Voltage Control for Ionization Measurement
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Solution Overview
Problem
Existing burner systems face challenges in maintaining a constant AC voltage at the ionization electrode, leading to systematic measurement errors due to component tolerances and nonlinear behavior, especially at high AC voltages, which affects the accuracy of air-fuel ratio control.
Innovation Solution
A closed-loop control system is implemented using a voltmeter connected in parallel with the ionization electrode, flame, and burner, where the voltage regulator adjusts the AC voltage to a setpoint, decoupling the air ratio control from voltage control, and incorporating a limiting resistor and measuring unit to manage parasitic currents, ensuring the maximum voltage is maintained across the ionization electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC voltage is increased to reduce dependence on parasitic elements, then measurement reliability improves, but systematic errors due to component tolerances increase
Solution Approach 1:
A closed-loop feedback circuit is implemented where a voltmeter measures the actual AC voltage at the ionization electrode and feeds this information to a voltage regulator. The regulator continuously adjusts the AC voltage source to maintain a predetermined setpoint voltage, automatically compensating for component tolerances and ensuring consistent measurement conditions.
Solution Approach 2:
The system dynamically adjusts the AC voltage parameter to maintain it at a predetermined level. By controlling the voltage parameter through feedback, the system optimizes the balance between having sufficiently high voltage to minimize parasitic element influence while avoiding excessive voltage that would amplify systematic errors from component tolerances.
2Measurement precision
If voltage control circuit is added to maintain constant AC voltage, then measurement precision improves, but device complexity increases
Solution Approach 1:
The voltage regulator circuit serves multiple functions: it controls the AC voltage to a setpoint, provides stable operating conditions for the ionization electrode, and compensates for line voltage fluctuations. This multi-functionality justifies the added complexity by delivering comprehensive benefits beyond simple voltage control.
Solution Approach 2:
A voltmeter is introduced as an intermediary measuring device that bridges the gap between the AC voltage source and the ionization electrode. It provides real-time voltage information to the regulator without significantly loading the circuit, enabling precise voltage control while maintaining circuit simplicity.
3Stability of the object's composition
If AC voltage is kept at constant magnitude through complex circuitry, then measurement stability improves, but ease of manufacture decreases
Solution Approach 1:
The voltage control system is designed to be self-regulating through feedback. The voltmeter continuously monitors the actual voltage and the regulator automatically adjusts the AC voltage source to maintain the setpoint, eliminating the need for complex manual calibration or precision components. The system self-corrects for variations in operating conditions.
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 solution allows for precise and reliable control of the AC voltage, reducing systematic errors and maintaining accurate air-fuel ratio control, even with high flame resistances or coatings, while keeping the system inexpensive and simple.
Implementation Method 1
When an AC voltage is applied, there flows through the electrode and flame an ionization current which is adjusted to a setpoint value specified as a function of the respective output of the burner
Implementation Method 2
A voltmeter is connected in parallel with a series circuit including the ionization electrode, the flame region, the burner and the input of an ionization current amplifier
Implementation Method 3
Described below is closed-loop control of AC voltage to a predefinable voltage setpoint with which the AC voltage used to measure an ionization current for fuel/air interconnection control can be kept sufficiently constant
Data Source
AI summary
A grounded burner, actuators adjusting the supply of fuel and air to the burner, an ionization electrode in the flame region, a flame amplifier at the ionization electrode generating an ionization signal, and a final control device are included in a burner system. During air ratio control mode, the final control device sets a first actuator and adjusts a second actuator. During voltage control mode a voltage regulator controls the AC voltage source using the AC voltage measured by the voltmeter, in conjunction with an ionization current amplifier. The voltmeter is connected in parallel with a sequence of the ionization electrode, the flame region, the burner and the input of the ionization current amplifier. The voltage regulator is connected to the voltmeter such that, during voltage control mode, the time-averaged current caused by the voltmeter through the connection is less than 5% of the time-averaged current through the ionization electrode.