SCR Catalyst Diagnostic Segmentation for Emission Control
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Solution Overview
Problem
Current SCR catalyst systems face challenges in efficiently diagnosing and monitoring both SCR catalyst devices in series, particularly in reducing emissions and increasing diagnostic frequency, with existing methods often restricting active diagnosis to fault detection and struggling to effectively monitor the second catalyst device.
Innovation Solution
A diagnostic method that differentiates between active and passive diagnostic methods for the two SCR catalyst devices, allowing for simultaneous or alternate monitoring, with active diagnosis on one device and passive on the other, using NH3 storage capacity analysis and metering strategies to minimize emissions impact on the overall system, and enabling more frequent diagnostics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active diagnostic method is applied to both SCR catalyst devices, then diagnostic precision is improved, but emissions increase due to reducing agent metering interventions
Solution Approach 1:
The patent divides the SCR catalyst system into two separate catalyst devices (first SCR catalyst device and second SCR catalyst device) with separate injection positions. This segmentation allows differentiated diagnostic approaches: active diagnosis on the first device and passive diagnosis on the second device, thereby limiting emissions impact while maintaining diagnostic precision for the overall system.
2Object-generated harmful factors
If passive diagnostic method is used for both SCR catalyst devices, then emissions impact is reduced, but diagnostic frequency and precision decrease
Solution Approach 1:
By segmenting the diagnostic approach across two catalyst devices, the system can apply active diagnosis (with higher frequency and precision) to the first device while using passive diagnosis on the second device. This segmented strategy increases overall diagnostic frequency without requiring both devices to undergo emissions-intensive active diagnosis simultaneously.
3Device complexity
If single SCR catalyst device is monitored, then device complexity is reduced, but monitoring precision of the second catalyst device is insufficient
Solution Approach 1:
The patent implements segmentation by creating two catalyst devices with separate injection positions and differentiated diagnostic methods. This allows the second catalyst device to be specifically monitored using passive diagnostic methods tailored to its position downstream of the first catalyst, improving monitoring precision without excessive complexity.
Solution Approach 2:
Different diagnostic methods are applied to different locations in the system: active diagnosis is applied to the first catalyst device where reducing agent is injected upstream, while passive diagnosis is applied to the second catalyst device downstream. This local differentiation optimizes monitoring precision for each device's specific operational context.
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 reduces the overall emissions effect, allows for more frequent diagnostics, and enables robust monitoring of both catalyst devices, particularly improving the second SCR catalyst device's monitoring capabilities, while maintaining minimal emissions impact.
Implementation Method 1
The basic principle of the SCR catalyst consists in that nitrogen oxide molecules are reduced to elementary nitrogen on the catalyst surface in the presence of ammonia (NH3) as a reducing agent
Implementation Method 2
Currently known SCR catalysts store NH3 on the catalyst surface. The NH3 stored on the catalyst surface is described as the NH3 filling level
Data Source
AI summary
In a method for diagnosing an SCR catalyst system of an internal combustion engine, the SCR catalyst system comprises at least one first SCR catalyst device (20) and at least one second SCR catalyst device (30). A first injection position upstream of the first SCR catalyst device (20) in the form of a first metering device (40) is provided for injecting liquid reducing agent for the SCR catalyst devices (20, 30). A second injection position between the two SCR catalyst devices (20, 30) in the form of a second metering device (50) is furthermore provided. Both SCR catalyst devices (20, 30) are monitored in a differentiated way by means of active and passive diagnostic methods.