NO Oxidation Catalyst Function Testing via Reducing Agent Concentration
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Solution Overview
Problem
Existing methods for testing the function capacity of NO oxidation catalysts in internal combustion engines are inefficient, particularly at low temperatures, and can cause damage or measurement inaccuracies due to high thermal loads and the need for large hydrocarbon additions, which also affect downstream exhaust gas treatment components.
Innovation Solution
A method that involves changing the concentration of a reducing agent in the exhaust gas flow upstream of the NO oxidation catalyst, measuring the resulting NOx concentration change, and evaluating it to assess the catalyst's function capacity, using NOx sensors and adjusting engine parameters like fuel injection and exhaust gas recirculation to generate carbon monoxide or hydrocarbons for oxidation, thereby determining the catalyst's oxidation capacity without causing excessive thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large quantities of hydrocarbons are added to test the catalyst, then the temperature rise for detection is sufficient, but fuel consumption increases and thermal load on the catalyst becomes excessive
Solution Approach 1:
The patent extracts the essential testing function from the problematic hydrocarbon addition method. Instead of adding large quantities of hydrocarbons to generate temperature rise, the system uses the naturally occurring reducing agents (CO, HC) already present in the exhaust gas at controlled concentrations, combined with precise temperature measurement. This separates the measurement function from the energy-intensive hydrocarbon addition, resolving the contradiction between measurement precision and fuel consumption.
Solution Approach 2:
The patent creates a controlled test condition that copies the essential elements of the original method (reducing agent presence, temperature measurement) while eliminating the harmful excesses. By using stoichiometric or near-stoichiometric engine operation to generate appropriate reducing agent concentrations without excessive hydrocarbon addition, the system replicates the necessary test conditions with minimal energy loss.
2Measurement precision
If large quantities of hydrocarbons are added to test the catalyst, then the temperature rise for detection is sufficient, but thermal load on the catalyst becomes excessive
Solution Approach 1:
The patent extracts the temperature measurement function from the harmful context of excessive hydrocarbon addition. By using controlled, stoichiometric engine operation to generate moderate reducing agent concentrations and measuring the resulting temperature rise from controlled oxidation, the system achieves sufficient temperature detection accuracy without subjecting the catalyst to excessive thermal load.
Solution Approach 2:
The patent changes the operating parameters of the engine during testing - specifically maintaining stoichiometric or near-stoichiometric air-fuel ratios and controlling reducing agent concentrations within safe ranges. This parameter control ensures that the temperature rise is sufficient for measurement while keeping the thermal load on the catalyst within acceptable limits, preventing damage.
3Quantity of substance
If the engine is run rich to generate reducing agents, then sufficient CO and HC are available for oxidation testing, but soot emissions and thermal load on the engine increase undesirably
Solution Approach 1:
The patent changes the engine operating parameters to achieve stoichiometric or near-stoichiometric air-fuel ratios during testing, rather than running rich. This parameter adjustment provides sufficient reducing agent concentrations (CO and HC) for oxidation testing while avoiding the harmful effects of rich operation, specifically soot emissions and excessive thermal load on the engine.
Solution Approach 2:
The patent converts the normally harmful effect of rich operation (excessive soot and thermal load) into a beneficial testing condition by using controlled stoichiometric operation. This generates adequate reducing agents for testing without the harmful side effects, effectively transforming the problem of reducing agent generation into a controlled, beneficial process.
4Quantity of substance
If the engine is run rich to generate reducing agents, then sufficient CO and HC are available for oxidation testing, but thermal load on the engine increases
Solution Approach 1:
The patent changes the engine operating parameters to maintain stoichiometric or near-stoichiometric air-fuel ratios during testing, rather than running rich. This provides sufficient reducing agent concentrations (CO and HC) for oxidation testing while keeping the thermal load on the engine at acceptable levels, avoiding the energy waste and thermal stress associated with rich operation.
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 method allows for reliable testing of NO oxidation catalyst function at low temperatures with reduced fuel consumption and minimal thermal load, providing accurate assessments of catalyst performance and triggering fault messages for malfunction, thus maintaining engine efficiency and preventing damage.
Implementation Method 1
the reducing agent is oxidised by means of the NOx contained in the exhaust gas flow so that there is a change in NOx concentration within and/or downstream after the NO oxidation catalyst
Implementation Method 2
In the NO oxidation catalyst, the reducing agent is oxidised by means of the NOx contained in the exhaust gas flow
Data Source
AI summary
The invention concerns a method and a device for testing the function capacity of an NO oxidation catalyst (5) which is used to reduce nitrous oxides (NOx) contained in the exhaust gas flow of an internal combustion engine (1) operated with air surplus. In the exhaust gas flow which is supplied to the NO oxidation catalyst (5), a change is made in the concentration of a reducing agent and the resulting change in NOx concentration in the exhaust gas flow within the NO oxidation catalyst (5) and/or downstream after the NO oxidation catalyst (5) is determined and used to test its function capacity.