Optical Air Ratio Sensor with Permeable Inlet
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Solution Overview
Problem
Existing air ratio sensors for fuel gas/air mixtures are limited by slow reaction times, high production costs, and significant dead time, making them inefficient and costly for accurate combustion control.
Innovation Solution
An optical sensor system with a restricted measuring space that uses a permeable inlet for the fuel gas/air mixture, an electrically operated excitation means to induce controlled chemical reactions, and an optical detection device to measure radiation intensity, allowing for rapid and cost-effective determination of the air ratio without uncontrolled ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrochemical measuring cells (Lambda sensors) are used for air ratio detection, then measurement functionality is achieved, but reaction time is slow and dead time is significant
Solution Approach 1:
The patent replaces electrochemical measuring cells with an optical detection system. A light source emits radiation through the gas mixture, and a photodetector measures absorption at specific wavelengths. This optical method eliminates the slow electrochemical reaction processes, achieving rapid response times while maintaining measurement accuracy for air ratio detection.
Solution Approach 2:
The patent utilizes the absorption characteristics of gas molecules at different wavelengths of light. By detecting how the gas mixture absorbs specific wavelengths (particularly around 4.3 μm for CO2), the system determines air ratio through optical phase interaction rather than chemical reaction, enabling fast response without dead time.
2Measurement precision
If electrochemical measuring cells are used for air ratio detection, then measurement functionality is achieved, but production costs are very high
Solution Approach 1:
The patent replaces expensive electrochemical sensors with a cost-effective optical system using standard light sources (such as infrared LEDs or lasers) and photodetectors. These optical components are commercially available at lower costs and do not require complex electrochemical cell assemblies, significantly reducing production expenses while maintaining measurement precision.
Solution Approach 2:
The system detects air ratio by measuring optical absorption parameters at specific wavelengths rather than using expensive electrochemical parameters. This parameter change approach allows the use of simpler, cheaper components while achieving the same measurement functionality through physical optical properties of the gas mixture.
3Measurement precision
If a larger measuring space is used to allow sufficient reaction, then measurement accuracy improves, but turbulence from the on-flowing mixture is transferred into the measuring chamber
Solution Approach 1:
The patent replaces chemical reaction-based measurement with direct optical absorption measurement. The light beam passes through the gas mixture without requiring a large reaction volume. This eliminates turbulence issues entirely, as the optical path can be made compact and the measurement is based on light-gas interaction rather than bulk chemical reactions that require stable, homogeneous conditions.
Solution Approach 2:
The patent transitions from a volumetric measurement approach (requiring large spaces for complete reaction) to a line-integral optical path approach. The light travels through a defined path through the gas, measuring absorption along this dimension. This dimensional change allows accurate measurement in a compact space without turbulence, as the optical method is insensitive to local flow variations.
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
The system enables rapid and accurate detection of the air ratio with minimal dead time and favorable costs, ensuring efficient and low-pollutant combustion processes by controlling chemical reactions within a quenching distance, preventing uncontrolled ignition and allowing for continuous operation with low combustion product discharge.
Implementation Method 1
A transfer of mass between the measuring space in the housing and the fuel gas/air mixture flowing on the other side of the separating agent takes place at any time by means of diffusion processes
Implementation Method 2
An electrically operated excitation means is arranged within the measuring space. In this context, an electrically operated excitation means is understood to be any device that can effect an energy supply (or energy input) into the measuring space in order to induce a chemical reaction of a fuel gas/air mixture in the measuring space
Implementation Method 3
This chemical reaction is optically measured and the optical signals are evaluated
Data Source
AI summary
A sensor for determining an air ratio of a fuel gas/air mixture, wherein a housing is formed, which delimitates a measuring space. The housing has on one side a diffusion passage for coupling with a fuel gas/air mixture flow, wherein the diffusion passage is formed by a gas-permeable separating agent. An electrically operated excitation element is arranged for energy supply into the measuring space in order to induce a chemical reaction of a fuel gas/air mixture in the measuring space. At least one optical detection device is directed into the measuring space with its detection area, wherein the at least one optical detection device detects the intensity of radiation from the reaction position in at least a first wavelength range and produces a signal being allocated to the detected intensity, from which the air ratio is inferable.