SCR Catalyst Reducing Agent Metering via NO2 Concentration
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Solution Overview
Problem
The determination of the required amount of reducing agent for an SCR catalytic converter in exhaust gas cleaning systems is prone to errors and deviations due to uncertainties in efficiency estimation, leading to suboptimal NOx reduction and increased consumption of the reducing agent.
Innovation Solution
A method that determines the NO2 concentration between the oxidizing exhaust gas cleaning component and the SCR catalytic converter using operating parameters, allowing for a two-stage calculation that accounts for the effects of both components, thereby reducing the data acquisition effort and development costs when replacing or adapting system components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-stage calculation model is implemented to separate oxidizing component and SCR catalyst effects, then the data acquisition effort and development costs are reduced, but the measurement precision and reliability of efficiency estimation may be affected
Solution Approach 1:
The calculation model is segmented into two independent stages: first calculating the NO2 concentration after the oxidizing component, then using that result to calculate SCR catalyst efficiency. This segmentation allows each stage to be developed and calibrated independently, reducing overall data acquisition requirements while maintaining accuracy.
Solution Approach 2:
The NO2 concentration after the oxidizing component serves as an intermediary parameter that couples the two calculation stages. By introducing this intermediate measurement, the system can separately characterize each component's effect while maintaining the ability to predict overall system behavior.
2Adaptability or versatility
If the oxidizing exhaust gas cleaning component is replaced or adapted, then the system can be optimized for specific engine types or vehicles, but complete system re-characterization would require extensive efficiency measurements and NH3 level measurements
Solution Approach 1:
The system characterization is segmented so that only the oxidizing component stage needs re-characterization when that component is replaced. The SCR catalyst stage parameters remain valid and do not require re-measurement, significantly reducing adaptation time.
Solution Approach 2:
The two-stage calculation model performs preliminary characterization of each component separately during system development. This preliminary action creates reusable parameter sets that can be quickly applied when components are replaced, avoiding the need for complete re-characterization.
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 significantly reduces the development and adaptation effort for exhaust gas cleaning systems by implementing a modular calculation model, ensuring precise reducing agent metering and optimal NOx reduction with minimal hardware adjustments.
Implementation Method 1
a reaction with NH3 or with an NH3-releasing substance in an SCR catalytic converter is provided selective catalytic reduction of nitrogen oxides
Implementation Method 2
SCR catalytic converters store a certain amount of ammonia (NH3) on their surface through adsorption
Implementation Method 3
an oxidizing exhaust gas cleaning component... which increases an emergency proportion in the exhaust gas at the expense of an NO proportion in the exhaust gas
Data Source
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AI summary
Proposed is a method to determine a reducing agent amount (Rm) to be fed to an SCR catalyst (18) in an exhaust gas purification system (12) of an internal combustion engine (10) for the reduction of nitrogen oxides contained in the exhaust gas, wherein the reducing agent amount (Rm) is determined in relation to the operating parameters of the exhaust gas purification system (12) and wherein an effect of an oxidizing exhaust gas purifying component (16) is taken into account, said purifying component being located in the exhaust gas flow path prior to the SCR catalyst (18) and raising an NO2 fraction in the exhaust gas at the expense of an NO2 fraction in the exhaust gas. The method is characterized in that for the determination of the reducing agent amount (Rm), a measure (NC2/ NOx) for the NO2 concentration in the exhaust gas between the oxidizing exhaust gas purification component (16) and the SCR catalyst (18) is first determined from the operating parameters of the oxidizing exhaust gas purification component (16), and the reducing agent amount (Rm) is determined from operating parameters of the SCR catalyst (18) and from the measure (NO2/ NOx) for the NO2 concentration in the exhaust gas between the oxidizing exhaust gas purification component (16) and the SCR catalyst (18). Also, a control device (14) set up for the purposes of carrying out the method is proposed.