Exhaust Aftertreatment Emission Measurement Using Catalytic Segment Models
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Solution Overview
Problem
Conventional nitrogen oxide sensors used in exhaust gas aftertreatment systems for internal combustion engines have cross-sensitivity to ammonia, making accurate determination of nitrogen oxide emissions impossible in operating modes with an exhaust gas lambda value less than 1, particularly in gasoline engines.
Innovation Solution
A method and device that utilize a nitrogen oxide sensor on the output side of the exhaust gas aftertreatment system, combined with a conversion model, to determine nitrogen oxide and ammonia emissions by modeling the conversion of nitrogen oxide into ammonia across multiple catalytic converter segments, accounting for local operating conditions such as temperature, oxygen storage, and exhaust gas lambda value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional nitrogen oxide sensor is used on the output side of the exhaust gas aftertreatment system, then nitrogen oxide emissions can be detected in operating modes with exhaust gas lambda value greater than 1, but accurate determination of nitrogen oxide emissions becomes impossible in operating modes with exhaust gas lambda value less than 1 due to cross-sensitivity to ammonia
Solution Approach 1:
The exhaust gas aftertreatment system is divided into multiple catalytic converter segments arranged in series. Each segment's conversion characteristics are modeled separately to determine partial conversion indications, which are then combined to obtain the overall conversion indication. This segmentation allows the system to account for local operating conditions in different segments and resolve the measurement ambiguity caused by ammonia cross-sensitivity.
Solution Approach 2:
A conversion model is introduced as an intermediary between the nitrogen oxide sensor measurement and the final emission determination. The model uses operating parameters (temperature, oxygen storage, lambda value) to calculate a conversion indication that represents the extent of nitrogen oxide conversion to ammonia in the catalytic converter. This intermediary allows the system to differentiate between measured nitrogen oxide and formed ammonia, enabling accurate emission determination in all operating modes.
2Quantity of substance
If ammonia is formed in the exhaust gas (exhaust gas lambda value less than 1), then the nitrogen oxide sensor exhibits cross-sensitivity and cannot accurately measure nitrogen oxide emissions, but ammonia emissions also need to be monitored
Solution Approach 1:
The system uses feedback from the nitrogen oxide sensor measurement combined with the conversion model calculation to determine both nitrogen oxide and ammonia emissions. The conversion indication derived from the model provides feedback about the extent of nitrogen oxide conversion to ammonia, which is then used to interpret the sensor signal correctly. This feedback mechanism enables simultaneous monitoring of both emissions types even when ammonia is present and causing cross-sensitivity.
Solution Approach 2:
The system monitors changes in operating parameters (temperature, oxygen storage capacity, exhaust gas lambda value) to determine the conversion indication. By tracking these parameter changes through the catalytic converter segments, the system can calculate the extent of nitrogen oxide conversion to ammonia at different operating conditions. This parameter-based approach enables the system to adapt to different operating modes and accurately determine both nitrogen oxide and ammonia emissions.
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 accurate measurement of nitrogen oxide and ammonia emissions, allowing for optimized engine operation to minimize pollutant emissions, achieved through model-based evaluation of the sensor signal and consideration of cross-sensitivity to ammonia.
Implementation Method 1
Conventional nitrogen oxide sensors used in exhaust gas aftertreatment systems for internal combustion engines have cross-sensitivity to ammonia
Implementation Method 2
modeling the conversion of nitrogen oxide into ammonia across multiple catalytic converter segments
Data Source
AI summary
A method for determining a nitrogen oxide emission and an ammonia emission in the combustion exhaust gas of an engine system having an exhaust-gas-guided internal combustion engine using an output-side nitrogen oxide sensor having a cross-sensitivity to ammonia. The method including: detecting a measurement signal of the nitrogen oxide sensor; ascertaining a partial conversion indication for each of multiple catalytic converter segments arranged in series in the combustion exhaust gas depending on local operating conditions with the aid of a provided conversion model that maps a local operating condition on the partial conversion indication; determining a conversion indication from the multiple partial conversion indications; and ascertaining a nitrogen oxide emission and an ammonia emission depending on the measurement signal and the conversion indication.