NO2 Concentration Determination in Exhaust Gas
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Solution Overview
Problem
Conventional sensors for measuring nitrogen oxides (NOx) in combustion engine exhaust gases are not suitable for distinguishing between nitrogen monoxide (NO) and nitrogen dioxide (NO2), making it difficult to determine their concentrations and ratios accurately, which is crucial for controlling exhaust gas treatment processes.
Innovation Solution
A method using two nitrogen oxide sensors, one upstream and one downstream of an exhaust gas treatment element, to compare their output signals and determine the NO2 concentration and NO2/NO ratio, allowing for precise measurement of NO2 levels and their impact on exhaust gas treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional nitrogen oxide sensors are used to measure total NOx concentration, then the measurement covers both NO and NO2, but the sensors cannot distinguish between NO and NO2 concentrations
Solution Approach 1:
The exhaust tract is segmented into multiple measurement zones with sensors positioned at different locations (upstream of catalytic converter, downstream of catalytic converter, upstream of particulate filter, downstream of particulate filter). This spatial segmentation allows differentiation of NO and NO2 concentrations at various stages of the exhaust treatment process, enabling precise determination of NO2 concentration and its conversion ratio.
2Measurement precision
If NO2 concentration is to be determined accurately for controlling exhaust gas treatment, then selective NO2 measurement is needed, but conventional sensors only provide total NOx measurement
Solution Approach 1:
The catalytic converter acts as an intermediary element that selectively converts NO to NO2. By measuring total NOx concentration upstream and downstream of the catalytic converter, the change in NO2 concentration can be determined. The catalytic converter mediates the transformation, allowing indirect measurement of NO2 concentration and conversion efficiency without requiring complex selective sensors.
3Measurement precision
If multiple sensors are used to determine NO2 concentration and NO2/NO ratio, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The same type of nitrogen oxide sensor is used at multiple measurement points throughout the exhaust tract. Each sensor performs the same function (measuring total NOx concentration), but by positioning them at different locations and combining the measurements with knowledge of exhaust gas flow and catalytic converter behavior, the system determines multiple parameters including NO2 concentration, NO concentration, and NO2/NO ratio without requiring different sensor types.
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 determination of NO2 concentration and NO2/NO ratios, improving the operation and efficiency of exhaust gas aftertreatment systems by providing accurate data for soot charge monitoring, catalyst effectiveness, and reaction modeling, thus optimizing combustion engine performance and emissions control.
Implementation Method 1
a nitrogen oxide sensor that is sensitive with regard to nitrogen monoxide and nitrogen dioxide provides a nitrogen oxide output signal that correlates with a total nitrogen oxide concentration represented by the sum of the concentration of nitrogen monoxide and nitrogen dioxide
Implementation Method 2
an exhaust gas treatment system arranged in the exhaust tract with the capability for converting nitrogen monoxide to nitrogen dioxide and/or for converting nitrogen dioxide to nitrogen monoxide
Data Source
AI summary
In a method for determining an NO2 concentration and/or a concentration ratio of NO2 and NO in an exhaust tract of a combustion device, such as an internal combustion engine, an NOx sensor that is sensitive with respect to NO2 and NO is utilized, which provides a NOx output signal correlating with an NOx concentration representing the sum of the concentrations of NO2 and NO. In order to determine the NO2 concentration and/or the concentration ratio of NO2 and NO, the NOx output signal of a first NOx sensor, which is arranged upstream of an exhaust gas treatment element arranged in the exhaust tract and having the capability of converting NO to NO2 and/or converting NO2 to NO, is compared to the NOx output signal of a second NOx sensor, which is disposed downstream of the exhaust gas treatment element.