Gas Heater Air Ratio Control Using Ionization Current

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Solution Overview

Problem

Existing gas-powered heaters lack an efficient method to determine the air ratio for optimal combustion, leading to unstable heating flames and increased pollutant emissions.

Innovation Solution

A heater device equipped with a computing and evaluation unit that determines the air ratio based on input power and ionization current, utilizing a modulatable blower and fuel control valve to achieve precise control over combustion air and fuel supply, along with sensors for thermal efficiency and fluid flow measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gas-powered heaters use conventional control methods without precise air ratio determination, then the device complexity is reduced, but the combustion stability deteriorates and pollutant emissions increase

Engineering Contradiction:
Improvecombustion stabilityVSAvoidcontrol system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements a feedback mechanism where the ionization current signal from the flame is continuously monitored and fed back to the control unit. The control unit adjusts the air-to-fuel ratio based on this feedback signal, maintaining stable combustion. This closed-loop control system automatically compensates for variations in fuel composition and flow conditions, ensuring reliable combustion without requiring overly complex manual intervention systems.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent replaces conventional mechanical or manual air ratio adjustment mechanisms with an electronic control system that uses ionization current measurements. Instead of relying on mechanical linkages or manual throttles, the system uses electronic sensors to detect flame ionization and electronically actuates the air control valve, substituting mechanical systems with more precise electronic control while managing overall system complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Object-generated harmful factors

If the air ratio is not precisely controlled, then the ease of operation is improved, but the pollutant emissions increase and combustion efficiency decreases

Engineering Contradiction:
Improvepollutant emissionsVSAvoidair ratio control difficulty
Core Design Contradiction:
Object-generated harmful factorsVSEase of operation

Solution Approach 1:

The control system performs self-adjustment by automatically monitoring the ionization current and self-correcting the air-to-fuel ratio without requiring manual intervention. The system serves itself by using the flame's own ionization properties as the sensing mechanism, eliminating the need for external operators to manually adjust air intake or fuel flow to achieve clean combustion.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The ionization current acts as an intermediary parameter that links the combustion state to the control system. Instead of directly measuring complex combustion parameters like CO or NOx emissions, the system uses ionization current as an intermediate indicator that correlates with combustion quality, enabling indirect but effective control of pollutant emissions through a simpler measurement.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Measurement precision

If the heater operates across the entire power range without power-specific air ratio adjustment, then the device complexity is reduced, but the measurement precision of air ratio determination deteriorates

Engineering Contradiction:
Improveair ratio determination accuracyVSAvoidpower range control complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements dynamic air ratio control where the target air ratio and control parameters are adjusted based on the detected power level. The system transitions from static to dynamic operation by modifying control setpoints according to the operating conditions. At different power levels (low, medium, high), the control unit applies different air-to-fuel ratio targets, ensuring precise air ratio determination and optimal combustion efficiency across the entire power range.

Inventive Principle:
Principle #15Dynamics

4Ease of manufacture

If conventional air ratio determination methods are used, then the ease of manufacture is improved, but the combustion efficiency and stability deteriorate

Engineering Contradiction:
Improveheater manufacturing simplicityVSAvoidcombustion optimization
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the fundamental measurement parameter from conventional methods (such as oxygen sensing in exhaust or manual air flow measurement) to ionization current measurement of the flame itself. This parameter change enables more direct and accurate air ratio determination. The ionization current provides real-time information about the combustion state, allowing for continuous optimization of combustion efficiency and stability while maintaining manufacturing feasibility through the use of relatively simple ionization sensors.

Inventive Principle:
Principle #35Parameter changes

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 enables reliable and precise determination of the air ratio across the entire power range, ensuring optimized combustion with a stable heating flame, minimized pollutant emissions, and maximum efficiency.

Implementation Method 1

the control and / or regulating unit (12) is provided to determine an air ratio Ac of the combustion on the basis of an input power Pin and an ionization current I

Methodology Applied
Scientific EffectIonization: Ionisation

Data Source

PatentEP3359879A1Heater device and method for operating a heater device
Publication Date: 2018.08.15 BOSCH TERMOTECHA

AI summary

The invention relates to a heater device having at least one open-loop and/or closed-loop control unit (12) for determining an air ratio (λc) of a combustion process. According to the invention, the open-loop and/or closed-loop control unit (12) is provided for determining the air ratio (λc) on the basis of an input power (Pin) and an ionization current (I) in at least one operating state.